Method for producing a magnetic head, the magnetic head including a pair of magnetic core halves

Abstract

Method for producing a magnetic head of a pair of magnetic core halves combined with a nonmagnetic layer therebetween including forming a winding window in at least one of a pair of generally flat oxide magnetic plates, forming at least one underlying layer on each oxide magnetic plate, forming a metal magnetic thin film on the underlying layer containing magnetic crystalline particles having average volume Va and average surface area Sa fulfilling the relationship Sa>about 4.64 Va¾, forming a groove in a body including the oxide magnetic plate, underlying layer and metal magnetic thin film, and combining the body with another body including an oxide magnetic plate and a metal magnetic thin film with a nonmagnetic layer therebetween, where the metal magnetic thin film is formed in such a manner to prevent the oxide magnetic plates from cracking due to internal stress generated in the metal magnetic thin film.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a magnetic head which is satisfactory in the anti-corrosion characteristic and the input and output characteristic, and is sufficiently durable against cracking in a base thereof; a method for producing the magnetic head; a video recording and reproduction apparatus including the magnetic head, and a video camera including the magnetic head.

2. Description of the Related Art

As a magnetic head for VCRs or the like, a ferrite head including a magnetic core formed by combining a pair of ferrite sections together is conventionally used. Recently, in accordance with the improvement in the magnetic recording density, a metal-in-gap head (MIG head) has become often used. The MIG head uses a metal magnetic material having a more highly saturated magnetic flux density than that of ferrite for a portion in the vicinity of a recording/reproduction gap.

FIG. 8 schematically shows an exemplary conventional ferrite head 300 . FIGS 9 A through 9 D schematically show an exemplary conventional MIG head 400 .

With reference to FIG. 8 , the ferrite head 300 includes a pair of ferrite sections F 1 A and F 1 B, and a nonmagnetic layer N 1 and glass bonding sections G 1 both provided between the pair of ferrite sections F 1 A and F 1 B for combining the ferrite sections F 1 A and F 1 B.

With reference to FIGS. 9A through 9D , the MIG head 400 includes a pair of magnetic core halves MCA and MCB, and a nonmagnetic layer N 2 and glass bonding sections G 2 both provided between the pair of magnetic core halves MCA and MCB for combining the magnetic core halves MCA and MCB. The magnetic core half MCA includes a ferrite section F 2 A, at least one underlying layer (not shown) provided on the ferrite section F 2 A, and a metal magnetic thin film FM 2 provided between the underlying layer and the nonmagnetic layer N 2 . The magnetic core half MCB includes a ferrite section F 2 B, at least one underlying layer (not shown) provided on the ferrite section F 2 B, and a metal magnetic thin film FM 2 provided between the underlying layer and the nonmagnetic layer N 2 .

As a material for the metal magnetic thin films FM 2 , amorphous materials (e.g., Japanese Laid-Open Publication No. 63-120653), Fe—N-based materials, and Fe—C-based materials have been developed. The Fe—N-based materials and Fe—C-based materials are obtained by thermally treating an amorphous film mainly containing Fe to deposit microscopic crystals having a diameter of about 5 to about 20 nm (e.g., Hasegawa, Journal of the Magnetics Society of Japan, 14, pp. 319-322 (1990); and Nago, IEEE, Trans., Magn., Vol, 28, No. 5 (1992)).

Among these materials, materials obtained by depositing or growing microscopic crystalline particles having a magnetic metal composition and thus having a highly saturated magnetic flux density of 1.2 T or higher and a soft magnetic characteristic need to be improved in the anti-corrosion characteristic.

For this purpose, attempts have been made to add light elements having passivity to these materials. However, the light elements, which easily react with oxygen, nitrogen and the like, react with oxygen used for making crystals amorphous or microscopic and thus tend not to remain in the microscopic crystalline particles having the magnetic metal composition.

In order to overcome this problem, in addition to adding the light elements having passivity to the above-mentioned metal magnetic materials, the magnetic crystalline particles of these materials are each controlled to have a relatively large size and a relatively large surface area. The metal magnetic thin film thus developed has satisfactory magnetic characteristics, a highly saturated magnetic flux density, and a sufficient anti-corrosion characteristic (e.g., Japanese Laid-Open Publication No. 10-223435).

An MIG head is a composite device of ferrite, which is an oxide, and a metal magnetic thin film. Accordingly, the MIG head involves the problems that the ferrite base may be cracked by an internal stress generated in the metal magnetic thin film and that the magnetic characteristics may be deteriorated by a reaction at the interface between the ferrite base and the metal magnetic thin film. The above-mentioned problems are caused by the structure of the MIG head or the material characteristics of the metal magnetic thin film.

An optimum structure of a magnetic head varies in accordance with the material characteristics of the metal magnetic thin film. In order to improve the characteristics of the magnetic head, it is necessary to solve the problems of the cracks in the ferrite base and the deterioration of the magnetic characteristics as well as to improve the materials design.

SUMMARY OF THE INVENTION

According to one aspect of the invention, a magnetic head includes a pair of magnetic core halves; and a nonmagnetic layer provided between the pair of magnetic core halves for combining the pair of magnetic core halves. The pair of magnetic core halves each includes an oxide magnetic base, at least one underlying layer provided on the oxide magnetic base, and a metal magnetic thin film provided between the underlying film and the nonmagnetic layer. The metal magnetic thin film includes a magnetic film containing, as a major material, magnetic crystalline particles having an average volume Va and an average surface area Sa fulfilling the relationship of Sa>about 4.84 Va ⅔ . At least one of the pair of magnetic core halves has a winding window therein. The metal magnetic thin film is provided in such a manner as to prevent the oxide magnetic base from cracking due to an internal stress generated in the metal magnetic thin film.

In one embodiment of the invention, the metal magnetic thin film includes magnetic crystalline particles, which have an average length of a longer side of more than about 50 nm.

In one embodiment of the invention, the magnetic crystalline particles have at least one shape selected from the group consisting of a generally needle-like shape, a generally column-like shape, and a multiple-branch shape including the magnetic crystalline particles of the generally needle-like shape and the generally column-like shape; and the magnetic crystalline particles having the generally needle-like shape and the generally column-like shape have an average length of a shorter side of more than about 5 nm and less than about 60 nm.

In one embodiment of the invention, where dS is an average length of a shorter side of the magnetic crystalline particles and dL is an average length of a longer side of the magnetic crystalline particles, 5 nm<dS<60 nm and 60 nm<dL<5000 nm.

In one embodiment of the invention, the metal magnetic thin film has a composition represented by (M a X b Z c ) 100-d A d , where M includes at least one magnetic metal element selected from the group consisting of Fe, Co and Ni; X includes at least one element selected from the group consisting of Si, Al, Ga and Ge; Z includes at least one element selected from the group consisting of elements of group IVa, elements of group Va, Al, Ga and Cr; A includes at least one element selected from the group consisting of O and N; and a, b, c and d fulfill the relationships of about 0.1≦b≦about 26, about 0.1≦c≦about 5, a+b+c=100, and about 1≦d≦about 10.

In one embodiment of the invention, the pair of magnetic core halves each have a combining surface which is combined with the other magnetic core half with the nonmagnetic layer interposed therebetween, a recording medium running surface on which a recording medium runs, and outer side surfaces continuous from the combining surface and from the recording medium running surface; and the metal magnetic thin film is not provided on the outer side surfaces.

In one embodiment of the invention, the metal magnetic thin film has a composition represented by (Fe a Si b Al c T d ) 100-e N e where T includes at least one element selected from the group consisting of Ti and Ta; and a, b, c, d and e fulfill the relationships of about 10≦b≦about 23, about 0.1≦d≦about 5, about 0.1≦c+d≦about 8, a+b+c+d=100, and about 1≦e≦about 10.

In one embodiment of the invention, Z includes at least one element selected from the group consisting of elements of group IVa, elements of group Va and Cr.

In one embodiment of the invention, X includes at least one element selected from the group consisting of Si and Ge; and a, b, c and d fulfill the relationships of about 0.1≦b≦about 23, about 0.1≦c≦about 8, a+b+c=100, and about 1≦d≦about 10.

In one embodiment of the invention, the metal magnetic thin film has a composition represented by (Fe a Si b Al c T d ) 100-e-f N e O f where a, b, c, d, e and f fulfill the relationships of about 10≦b≦about 23, about 0.1≦d≦about 5, about 0.1≦c+d≦about 8, a+b+c+d=100, and about 1≦e+f≦about 10, and 0.1≦f≦about 5.

In one embodiment of the invention, the at least one underlying layer contains at least one of an oxide of Al, and oxide of Si, a nitride of Al, a nitride of Si, and a mixture thereof.

In one embodiment of the invention, the at least one underlying layer includes a first underlying layer in contact with the magnetic core half and a second underlying layer in contact with the metal magnetic thin film. The first underlying layer contains at least one of an oxide of Al, and oxide of Si, a nitride of Al, a nitride of Si, and a mixture thereof. The metal magnetic thin film contains at least one of oxygen and nitrogen; and the second underlying layer contains an element which is a main component of the metal magnetic thin film, and at least one of oxygen and nitrogen in a larger amount than the amount contained in the metal magnetic thin film. The second underlying layer contains crystalline particles. The crystalline particles have an average particle diameter of about 5 nm or less at least in the vicinity of an interface between the first underlying layer and the second underlying layer.

In one embodiment of the invention, the first underlying layer contains an oxide of Al, and has a thickness of about 0.5 nm or more and about 4 nm or less. The second underlying layer has a thickness of about 0.5 nm or more and about 200 nm or less.

In one embodiment of the invention, the oxide magnetic base of each of the magnetic core halves contains a ferrite single crystal. The ferrite single crystal has a combining surface corresponding to a combining surface of the magnetic core half which is combined with the other magnetic core half with the nonmagnetic layer interposed therebetween, and a recording medium running surface on which a recording medium runs.

In one embodiment of the invention, the ferrite single crystal includes an MnZn ferrite single crystal containing A mol % of Fe 2 O 3 , B mol % of MnO and C mol % of ZnO, where A, B and C fulfill the relationships of about 52≦A≦about 57, about 5≦B≦about 29, and about 16≦C≦about 21.

In one embodiment of the invention, the pair of magnetic core halves each have a combining surface which is combined with the other magnetic core half with the nonmagnetic layer interposed therebetween, and a recording medium running surface on which a recording medium runs. At least one of the pair of magnetic core halves has a bottom surface and a first inner side surface for forming the winding window. The first inner side surface extends from the bottom surface toward the combining surface and is provided on the side of the recording medium running surface with respect to the bottom surface. An angle made by the first inner side surface and the combining surface is about 22.5° or more and about 70° or less.

In one embodiment of the invention, the winding window is provided in one of the pair of magnetic core halves, and the angle made by the first inner side surface and the combining surface is about 45° or more and about 70° or less.

In one embodiment of the invention, the winding window is provided in both of the pair of magnetic core halves, and the angle made by the first inner side surface and the combining surface is about 22.5° or more and about 50° or less.

In one embodiment of the invention, the first inner side surface includes a second inner side surface adjacent to the combining surface and a third inner side surface adjacent to the bottom surface. An angle made by the second inner side surface and the combining surface is about 22.5° or more and about 70° or less. An angle made by the third inner side surface and the bottom surface is about 90°.

In one embodiment of the invention, the winding window is provided in one of the pair of magnetic core halves, and the angle made by the second inner side surface and the combining surface is about 45° or more and about 70° or less.

In one embodiment of the invention, the winding window is provided in both of the pair of magnetic core halves, and the angle made by the second inner side surface and the combining surface is about 22.5° or more and about 50° or less.

In one embodiment of the invention, the metal magnetic thin film has a composition represented by (Fe a Si b Al c Ti d ) 100-e-f N e O f , where a, b, c, d, e and f fulfill the relationships of about 10≦b≦about 13, about 1≦c≦about 3, about 1≦d≦about 3, a+b+c+d=100, about 4≦e+f≦about 10, and about 0.1≦f≦about 2.

In one embodiment of the invention, the oxide magnetic base of each of the magnetic core halves has a combining surface which is combined with the oxide magnetic base of the other magnetic core half with the nonmagnetic layer interposed therebetween, and side surfaces continuous from the combining surface. An angle made by the combining surface and each of the side surfaces is about 70° ore more and about 90° or less. The metal magnetic thin film is provided on the combining surface but is not provided on the side surfaces.

According to another aspect of the invention, a method for producing a magnetic head is provided. The magnetic head includes a pair of magnetic core halves, and a nonmagnetic layer provided between the pair of magnetic core halves for combining the pair of magnetic core halves. The pair of magnetic core halves each include an oxide magnetic base, at least one underlying layer provided on the oxide magnetic base, and a metal magnetic thin film provided between the underlying layer and the nonmagnetic layer. The metal magnetic thin film includes a magnetic film containing, as a major material, magnetic crystalline particles having an average volume Va and an average surface area Sa fulfilling the relationship of Sa>about 4.84 Va ⅔ . At least one of the pair of magnetic core halves has a winding window therein, and the metal magnetic thin film is provided in such a manner as to prevent the oxide magnetic base from cracking due to an internal stress generated in the metal magnetic thin film; wherein the metal magnetic thin film has a composition represented by (M a X b Z c ) 100-d A d , where M includes at least one magnetic metal element selected from the group consisting of Fe, Co and Ni, X includes at least one element selected from the group consisting of Si, Al, Ga and Ge, Z includes at least one element selected from the group consisting of elements of group IVa, elements of group Va, Al, Ga and Cr, and A includes at least one element selected from the group consisting of O and N, and a, b, c and d fulfill the relationships of about 0.1≦b≦about 26, about 0.1≦c≦about 5, a+b+c=100, and about 1≦d≦about 10. The metal magnetic thin film includes magnetic crystalline particles, the magnetic crystalline particles have at least one shape selected from the group consisting of a generally needle-like shape, a generally column-like shape, and a multiple-branch shape combining the generally needle-like shape and the generally column-like shape; and the magnetic crystalline particles have an average length dS of a shorter side of about 5 nm<dS<about 60 nm and an average length of a longer side of about 60 nm<dL<about 5000 nm. The method includes a winding window formation step of forming a winding window in at least one of a pair of oxide magnetic plates which are generally flat; an underlying layer formation step of forming at least one underlying layer on each of the pair of oxide magnetic plates; a metal magnetic thin film formation step of forming the metal magnetic thin film on the underlying layer, the metal magnetic thin film being formed using a solid material containing an element which is a main component of the metal magnetic thin film in an atmosphere containing at least one of oxygen and nitrogen by a gas phase technique; a track formation step of forming a groove in a body including the oxide magnetic plate, the underlying layer, and the metal magnetic thin film so that the groove has a width corresponding to a track; and a combining step of combining the body with another body including an oxide magnetic plate, an underlying layer, and a metal magnetic thin film, with the nonmagnetic layer interposed therebetween.

In one embodiment of the invention, the steps are performed in the order of the winding window formation step, the underlying layer formation step, the metal magnetic thin film formation step, the track formation step, and then the combining step.

In one embodiment of the invention, the steps are performed in the order of the underlying layer formation step, the metal magnetic thin film formation step, the winding window formation step, the track formation step, and then the combining step.

According to still another aspect of the invention, a video recording and reproduction apparatus includes a cylinder having any of the above-defined magnetic heads mounted thereon; a head/tape interface mechanism for winding a magnetic tape around the cylinder; a cylinder driving section for driving the cylinder; and a magnetic tape driving section for driving the magnetic tape wound around the cylinder.

According to still another aspect of the invention, a video camera includes a cylinder having any of the above-defined magnetic heads; a head/tape interface mechanism for winding a magnetic tape around the cylinder; a cylinder driving section for driving the cylinder; a magnetic tape driving section for driving the magnetic tape wound around the cylinder; an optical system for converting a video signal into an electric signal; and a signal processing circuit for outputting the electric signal obtained by conversion by the optical system to the magnetic head.

Thus, the invention described herein makes possible the advantages of providing a magnetic head which (i) is satisfactory in the anti-corrosion characteristic and an input and output characteristic and is sufficiently durable against cracking in a base and (ii) has an optimum combination of a metal magnetic thin film and a head structure; a method for producing the magnetic head; a video recording and reproduction apparatus including the magnetic head; and a video camera including the magnetic head.

These and other advantages of the present invention will become apparent to those skilled in the art upon reading and understanding the following detailed description with reference to the accompanying figures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a view of a surface of a magnetic head in a first example according to the present invention, on which a recording tape runs;

FIG. 1B is a cross-sectional view taken along line A 1 —A 1 in FIG. 1A ;

FIG. 1C shows another exemplary magnetic head in the first example according to the present invention,

FIG. 1D shows still another exemplary magnetic head in the first example according to the present invention;

FIG. 1E is a view of a surface of another magnetic head in a first example according to the present invention, on which a recording tape runs;

FIGS. 2A through 2D are isometric views illustrating a method for producing the magnetic head in the first example according to the present invention;

FIG. 3A is an enlarged partial cross-sectional view of a ferrite single crystal having a winding window shown in FIG. 2B ;

FIG. 3B is a cross-sectional view of a ferrite single crystal having a winding window shown in FIG. 1B ;

FIG. 3C is a flowchart illustrating a method for producing the magnetic head in the first example according to the present invention;

FIG. 4A is a view of a surface of a magnetic head in a second example according to the present invention, on which a recording tape runs;

FIG. 4B is a cross-sectional view taken along line A 2 —A 2 in FIG. 4A ;

FIG. 4C shows still another exemplary magnetic head in the second example according to the present invention,

FIG. 4D shows still another exemplary magnetic head in the second example according to the present invention;

FIG. 4E is a view of a surface of another magnetic head in a second example according to the present invention, on which a recording tape runs;

FIGS. 5A through 5D are isometric views illustrating a method for producing the magnetic head in the second example according to the present invention;

FIG. 5E is a flowchart illustrating a method for producing the magnetic head in the first example according to the present invention;

FIG. 6 is a block diagram showing a structure of a video recording and reproduction apparatus in a third example according to the present invention;

FIG. 7 is a block diagram showing a structure of a video camera in a fourth example according to the present invention;

FIG. 8 is a schematic isometric view showing an exemplary conventional ferrite head; and

FIGS. 9A through 9D are schematic views of an exemplary conventional MIG head.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, the present invention will be described by way of illustrative examples with reference to the accompanying drawings. Throughout the specification, identical elements bear identical reference numerals and the descriptions thereof will not be repeated.

EXAMPLE 1

FIGS. 1A and 1B schematically show a magnetic head 100 in a first example according to the present invention. FIG. 1A is a view of a surface of the magnetic head 100 , on which a recording tape runs (hereinafter, referred to as a “tape running surface”). FIG. 1B is a cross-sectional view taken along line A 1 —A 1 in FIG. 1 A.

With reference to FIGS. 1A and 1B , the magnetic head 100 includes a pair of magnetic core halves MC 1 and MC 2 , and a nonmagnetic layer N 3 and glass bonding sections G 3 both provided between the pair of magnetic core halves MC 1 and MC 2 for combining the magnetic core halves MC 1 and MC 2 . The magnetic core half MC 1 includes a ferrite section F 3 A, at least on underlying layer UL 1 ( FIG. 1A ) provided on the ferrite section F 3 A, and a metal magnetic thin film FM 3 provided between the underlying layer UL 1 and the nonmagnetic layer N 3 . The magnetic core half MC 2 includes a ferrite section F 3 B, at least one underlying layer UL 1 ( FIG. 1A ) provided on the ferrite section F 3 B, and a metal magnetic thin film FM 3 provided between the underlying layer UL 1 and the nonmagnetic layer N 3 . The magnetic core half MC 1 has a winding window 21 A.

With reference to FIG. 1A , the ferrite sections F 3 A and F 3 B each include a combining surface S 1 facing the nonmagnetic layer N 3 and outer side surfaces S 2 and S 3 continuous from the combining surface S 1 . In each of the ferrite sections F 3 A and F 3 B, the metal magnetic thin film FM 3 is provided only on the combining surface S 1 with the underlying layer UL 1 interposed therebetween, and is not provided on the outer side surfaces S 2 or S 3 for the following reason. An angle made by the combining surface S 1 and each of the side surfaces S 2 and S 3 is about 70° or more and about 90 20 or less.

In the case where the metal magnetic thin film FM 3 is provided on the outer side surfaces S 2 and S 3 , an undesirable internal stress is generated in the metal magnetic thin film FM 3 provided on the outer side surfaces S 2 and S 3 . Such an internal stress causes cracks in the ferrite sections F 3 A and F 3 B. The metal magnetic thin film FM 3 is provided in such a manner that the ferrite sections F 3 A and F 3 B are not cracked due to the undesirable internal stress. Each of the ferrite sections F 3 A and F 3 B includes a ferrite single crystal, for example, an MnZn ferrite single crystal. The MnZn ferrite single crystal includes A mol % of Fe 2 O 3 , B mol % of MnO and C mol % of ZnO, where A, B and C fulfill the relationships of about 52≦A≦about 57, about 5≦B≦about 29, and about 16≦C≦about 21. The MnZn ferrite single crystal can further include oxides of Ca, oxides of Ni and oxides of Cu.

FIG. 1C shows another exemplary magnetic head 100 A in the first example according to the present invention, and FIG. 1D shows still another exemplary magnetic head 100 B in the first example according to the present invention. The magnetic head 100 A shown in FIG. 1C includes a winding window 21 A in both of the magnetic core halves MC 1 . The magnetic head 100 B shown in FIG. 1D includes a winding window 21 , having a different shape from that of the winding window 21 A, in both of the magnetic core halves MC 3 .

In FIGS. 1B , 1 C and 1 D, the underlying layer UL 1 is omitted for simplicity.

Hereinafter, a method for producing the magnetic head 100 B will be described as an example of a method for producing the magnetic heads 100 , 100 A and 100 B, with reference to FIGS. 2A through 2D showing schematic isometric views and FIG. 3C illustrating a flowchart of the method.

FIG. 2A shows a plate-like rectangular parallelepiped MnZn ferrite single crystal having the surfaces S 21 , S 22 and S 23 . The surfaces S 21 , S 22 and S 23 each have a crystalline orientation of substantially (100). In step S 101 (FIG. 3 C), the MnZn ferrite single crystal shown in FIG. 2A is processed so as to have a shape shown in FIG. 2B having the winding window 21 . More specifically, the surface S 21 is cut and polished and then a layer, the properties of which have been changed by the cutting and polishing, is removed. When producing the magnetic core half MC 2 (FIG. 1 B), no winding window is produced. When producing the magnetic core half MC 1 , the winding window 21 A is produced.

Due to the general characteristics of a magnetic head, the surface S 21 is preferably a (100) plane, and surfaces S 22 and S 23 are preferably (100) or (110) planes. Considering the friction of the magnetic head with the magnetic tape which occurs in operation, it is more preferable for the surface S 23 to be a (100) plane than a (110) plane. When the surfaces S 21 and S 23 are both (100) planes, the surface S 22 is inevitably a (100) plane.

On a practical level, it is difficult to form the surfaces S 21 , S 22 and S 23 to be precisely (100) or (110) planes, but a substantially equivalent effect is obtained when the error of the crystal orientation of the surfaces S 21 , S 22 and S 23 is ±4°.

FIG. 3A is an enlarged partial cross-sectional view of the ferrite single crystal having the winding window 21 shown in FIG. 2 B. FIG. 3B is a cross-sectional view of a ferrite single crystal having the winding window 21 A (FIG. 1 B). The cross-sectional shape of the winding window 21 shown in FIG. 3A is inclined only in the vicinity of the combining surface S 1 (S 21 in FIG. 2 B). Due to such an inclination, the magnetic flux is narrowed and thus the characteristics of a magnetic head are improved.

The winding window 21 A shown in FIG. 3B has a first inner side surface S 1 A and a bottom surface S 1 B. The first inner side surface S 1 A is extended from the bottom surface S 1 B toward the combining surface S 1 and is provided on the side of the recording medium running surface with respect to the bottom surface. Angle θ 1 made by the combining surface S 1 and the first inner side surface is equal to angle θ 2 made by the bottom surface S 1 B and the first inner side surface S 1 A; i.e., θ 1 =θ 2 . In the magnetic head 100 ( FIG. 1B ) having the winding window 21 A in only one of the two magnetic core halves (i.e., the magnetic core half MC 1 ), a favorable result of narrowing the magnetic flux is obtained when θ 1 =about 45° to about 70°. In the magnetic head 100 A ( FIG. 1C ) having the winding window 21 A in both of the two magnetic core halves MC 1 , a favorable result of narrowing the magnetic flux is obtained when θ 1 =about 22.5° to about 50°.

The size of the winding window 21 A is determined so that a required number of turns can be provided. Where two winding windows allowing an identical number of turns are compared, the winding window having a shorter magnetic path when seen from the tape running surface provides a higher level of reproduction sensitivity of the magnetic head.

In order to shorten the magnetic path while keeping the effect of narrowing the magnetic flux, the winding window 21 shown in FIG. 3A is preferable. The winding window 21 includes the bottom surface S 1 B and, the side corresponding to the first inner side surface S 1 A in FIG. 3B is divided into a second inner side surface S 1 C and a third inner side surface S 1 D. Angle θ 11 made by the combining surface S 1 and the second inner side surface S 1 B is different from θ 12 made by the third inner side surface S 1 D and the bottom surface S 1 B.

Angle θ 11 , which relates to narrowing of the magnetic flux, provides a favorable result in the same range as described above. In other words, in the magnetic head having the winding window 21 in only one of the two magnetic core halves (not shown), a favorable result of narrowing the magnetic flux is obtained when θ 11 =about 45° to about 70°. In the magnetic head 100 B ( FIG. 1D ) having the winding window 21 in both of the two magnetic core halves MC 3 , a favorable result of narrowing the magnetic flux is obtained when θ 11 =about 22.5° to about 50°.

Angle θ 12 is preferably substantially 90° as shown in FIG. 3A in order to keep the size of the winding window 21 required for a desired number of turns of winding while shortening the magnetic path.

After the winding window (e.g., 21 ) is formed, the underlying layer UL 1 ( FIG. 1A ) of alumina is formed on the combining surface S 1 in step S 102 (FIG. 3 C). The underlying layer UL 1 is formed since formation of the metal magnetic thin film FM 3 directly on the ferrite (i.e., oxide) sections F 3 A and F 3 B undesirably causes oxygen to diffuse during heat treatment. Other materials favorably usable for the underlying layer UL 1 include oxides of silicon, oxides of aluminum, nitrides of aluminum, nitrides of silicon, and mixtures thereof. The underlying layer UL 1 preferably has a thickness of about 0.5 nm or more to prevent the diffusion of oxygen. The effect of preventing the diffusion of oxygen is better as the underlying layer UL 1 is thicker, but the magnetic flux leaks when the underlying layer UL 1 is too thick since the materials favorable for the underlying layer UL 1 are nonmagnetic. The leaking of the magnetic flux deteriorates the characteristics of the magnetic head. Accordingly, the thickness of the underlying layer UL 1 is preferably about 4 nm or less.

In step S 103 (FIG. 3 C), the metal magnetic thin film FM 3 is formed on the underlying layer UL 1 . A more favorable effect is provided by forming a second underlying layer UL 2 ( FIG. 1E ) having a thickness of about 0.5 nm or more to about 200 nm or less, preferably about 0.5 nm to about 20 nm, before the metal magnetic thin film FM 3 is formed. The amount of each of oxygen and nitrogen contained in the second underlying layer UL 2 is larger than that contained in the metal magnetic thin film FM 3 . The metal magnetic thin film FM 3 is formed using a solid material. FIG. 2C shows the resultant body. In FIG. 2 C and FIG. 2D (described below), the underlying layer UL 1 and UL 2 are omitted for simplicity.

After a nonmagnetic gap layer (not shown) is formed on the metal magnetic thin film FM 3 , a groove or grooves 22 (i.e., track or tracks) are formed for regulating the width of a track in step S 104 (FIG. 3 C). FIG. 2D shows the resultant body. Then, the nonmagnetic layer N 3 is formed on the body shown in FIG. 2 D.

In step S 105 (FIG. 3 C), the resultant body with the nonmagnetic layer N 3 is properly positioned to face another identical body, and a bonding glass material is caused to flow by the heat treatment performed in an inactive gas atmosphere to bond the two bodies. In step S 106 (FIG. 3 C), the resultant assembly is cut into a desired shape and polished. Thus, the magnetic head 100 B ( FIG. 1D ) including the two magnetic core halves MC 3 is obtained. The magnetic heads 100 ( FIG. 1B ) and 100 A ( FIG. 1C ) are obtained in a similar manner with appropriate changes.

For forming the magnetic head according to the present invention, usual methods are usable. For example, cutting can be performed using a dicing saw including a resin bond diamond blade or a metal resin bond diamond blade, a slicing saw or the like. Polishing can be performed by, for example, rotation lapping using green carbon (SiC) grindstone or diamond grindstone in combination with a cast iron or tin surface plate, or using a lapping tape including an organic resin tape and alumina or diamond grindstone dispersed thereon.

When necessary, a layer of the ferrite, the properties of which have been changed, can be removed by, for example, acid surface etching using phosphoric acid or the like, or mechanochemical lapping using a low weight tin surface plate in combination with colloidal silica grindstone adjusted to be weakly acidic.

The underling layers UL 1 and UL 2 and the nonmagnetic layer for combining the magnetic core halves according to the present invention can be formed by usual gas phase film formation methods, for example, by sputtering such as high frequency magnetron sputtering, counter target sputtering, ion beam sputtering, ECR sputtering or the like, or by CVD.

The metal magnetic thin film can be formed in a low gas pressure atmosphere by sputtering, for example, high frequency magnetron sputtering, DC sputtering, counter target sputtering, ion beam sputtering, ECR sputtering, or the like.

The metal magnetic thin film is specifically produced as follows. An alloy target, having a composition determined in consideration of a possible offset in the composition from the composition intended according to the present invention, is formed on a base by sputtering using an inactive gas such as argon or the like. A portion of an additive can be provided on the alloy target as a pellet and sputtered together with the alloy target. Alternatively, a portion of the additive can be introduced into the sputtering apparatus in a gaseous state and reactive sputtering can be performed.

The pair of magnetic core halves can be bonded together by glass bonding using a bonding glass material, which is usually used for ferrite heads and MIG heads. For example, a bonding glass material selected from bonding glass materials having a softening point of about 460° C. to about 560° C. is heat-treated at a temperature selected from the range of softening point ±40° C. and caused to flow in at least two portions around the magnetic core halves to be bonded. The bonding glass material is then cured. Thus, the magnetic core halves are combined together.

As described above, in the first example according to the present invention, the metal magnetic thin film FM 3 is provided only on the combining surface S 1 of each of the magnetic core halves and not on the outer side surface S 2 or S 3 . Consequently, the ferrite sections F 3 A and F 3 B are prevented from cracking by the undesirable internal stress in the metal magnetic thin film FM 3 .

Therefore, according to the present invention, a magnetic head which is satisfactory in the anti-corrosion characteristic and input and output characteristic and is durable against cracks and a method for producing such a magnetic head are provided.

EXAMPLE 2

FIGS. 4A and 4B schematically show a magnetic head 200 in a second example according to the present invention. FIG. 4A is a view of a tape running surface of the magnetic head 200 . FIG. 4B is a cross-sectional view taken along line A 2 —A 2 in FIG. 4 A. The magnetic head 200 includes two magnetic core halves MC 4 and MC 5 , and includes a winding window 21 A in one of the magnetic core halves (i.e., the magnetic core half MC 4 ).

FIG. 4C shows another exemplary magnetic head 200 A in the second example according to the present invention, and FIG. 4D shows still another exemplary magnetic head 200 B in the second example according to the present invention. The magnetic head 200 A shown in FIG. 4C includes a winding window 21 A in both of the magnetic core halves MC 4 . The magnetic head 200 B shown in FIG. 4D includes two magnetic core halves MC 5 and MC 6 , and includes a winding window 21 A, in one of the magnetic core halves (i.e., the magnetic core half MC 6 ).

In FIGS. 4B , 4 C and 4 D, the underlying layer UL 1 is omitted for simplicity.

Hereinafter, a method for producing the magnetic head 200 B will be described as an example of a method for producing the magnetic heads 200 , 200 A and 200 B, with reference to FIGS. 5A through 5D showing schematic isometric views and FIG. 5C illustrating a flowchart of the method.

FIG. 5A shows a rectangular parallelepiped MnZn ferrite single crystal having the surfaces S 21 , S 22 and S 23 . The MnZn ferrite single crystal shown in FIG. 5A is cut and polished so as to have a shape shown in FIG. 5 B. The surface S 21 is polished and then the layer, the properties of which have been changed by the cutting and polishing, is removed. In step S 201 (FIG. 5 E), and underlying layer UL 1 ( FIG. 4A ) of alumina is formed on the combining surface S 1 . Other materials usable for the underlying layer include oxides of silicon, oxides of aluminum, and nitrides of aluminum, nitrides of silicon, and mixtures thereof as in the first example.

In step S 202 (FIG. 5 E), the metal magnetic thin film FM 3 is formed on the underlying layer UL 1 . A more favorable effect is provided by forming a second underlying layer UL 2 ( FIG. 4E ) having a thickness of about 0.5 nm or more to about 200 nm or less, preferably about 0.5 nm to about 20 nm, and an average particle diameter of about 5 nm or less in the vicinity of the interface with the underlying layer UL 1 is formed before the metal magnetic thin film FM 3 is formed. The amount of each of oxygen and nitrogen contained in the second underlying layer UL 2 is larger than that contained in the metal magnetic thin film FM 3 . FIG. 5C shows the resultant body. In FIG. 5 C and FIG. 5D (described below), the underlying layers UL 1 and UL 2 are omitted for simplicity.

After a nonmagnetic gap layer (not shown) is formed on the metal magnetic thin film FM 3 , the winding window 21 is formed in step S 203 (FIG. 5 E). When producing the magnetic core half MC 5 (FIG. 4 B), no winding window is produced. When producing the magnetic core half MC 4 (FIG. 4 B), the winding window 21 A of a different shape is produced. The winding window 21 can have the same shape as that in the first example.

In step S 204 (FIG. 5 E), a groove or grooves 22 (i.e., track or tracks) are formed for regulating the width of a track. FIG. 5D shows the resultant body. Then, the nonmagnetic layer N 3 is formed on the body shown in FIG. 5 D. In step S 205 (FIG. 5 E), the resultant body with the nonmagnetic layer N 3 is properly positioned to face another body without any winding window, and a bonding glass material is caused to flow by the heat treatment performed in an inactive gas atmosphere to bond the bodies. In step S 206 (FIG. 5 E), the resultant assembly is cut into a desired shape and polished. Thus, the magnetic head 200 B ( FIG. 4D ) including the magnetic core halves MC 6 and MC 5 is obtained. The magnetic head 200 ( FIG. 4B ) and 200 A ( FIG. 4C ) are obtained in a similar manner with appropriate changes.

As described above, in the second example according to the present invention, the metal magnetic thin film FM 3 is provided only on the combining surface S 1 of each of the magnetic core halves and not on the outer side surface S 2 or S 3 . Consequently, the ferrite sections F 3 A and F 3 B are prevented from cracking by the undesirable internal stress in the metal magnetic thin film FM 3 .

Therefore, according to the present invention, a magnetic head which is satisfactory in the anti-corrosion characteristic and input and output characteristic and is durable against cracks and a method for producing such a magnetic head are provided.

EXAMPLE 3

FIG. 6 is a block diagram of a video recording and reproduction apparatus 800 including a plurality of magnetic heads 100 in the first example according to the present invention.

The video recording and reproduction apparatus 800 includes the magnetic heads 100 , a cylinder 801 for securing the magnetic heads 100 , a head/tape interface mechanism 805 for winding a magnetic tape 804 around the cylinder 801 , a cylinder driving section 802 for rotating the cylinder 801 , and a magnetic tape driving section 803 for driving the magnetic tape 804 wound around the cylinder 801 .

The video recording and reproduction apparatus 800 performs recording or reproduction of a video signal or an audio signal as follows.

The cylinder driving section 802 rotates the cylinder 801 at a constant rate. The magnetic tape driving section 803 feeds the magnetic tape 804 from one reel at a constant rate so that the magnetic tape 804 runs along the cylinder 801 and then is wound around another reel. The head/tape interface mechanism 805 acts to wind the magnetic tape 804 around the cylinder 801 obliquely.

When the cylinder 801 starts rotating, the magnetic heads 100 scan the magnetic tape 804 at a constant cycle. During a recording operation, the magnetic heads 100 convert an input electric signal into a magnetic flux to change the magnetization state of a magnetic material on the magnetic tape 804 . Thus, recording is performed. During a reproduction operation, the magnetic heads 100 convert a magnetic flux on the magnetic tape 804 into an electric signal.

According to the present invention, a video recording and reproduction apparatus including a magnetic head which is satisfactory in the anti-corrosion characteristic and input and output characteristic and is durable against cracks is provided.

EXAMPLE 4

FIG. 7 is a block diagram of a video camera 900 including a plurality of magnetic heads 100 in the first example according to the present invention.

The video camera 900 includes the magnetic heads 100 , a cylinder 801 for securing the magnetic heads 100 , a head/tape interface mechanism 805 for winding a magnetic tape 804 around the cylinder 801 , a cylinder driving section 802 for rotating the cylinder 801 , a magnetic tape driving section 803 for driving the magnetic tape 804 wound around the cylinder 801 , an optical system 901 for converting a video signal into an electric signal, a microphone 902 for converting an audio signal into an electric signal, a signal processing circuit 904 for outputting the electric signals from the optical system 901 and the microphone 902 to the magnetic heads 100 , and a liquid crystal monitor 903 for displaying a video signal.

The video camera 900 performs recording or reproduction of a video signal or an audio signal in a similar manner to that in the third example.

During a recording operation, the video signal and the audio signal are recorded on the magnetic tape 804 by the magnetic heads 100 and also displayed on the liquid crystal monitor 903 . During a reproduction operation, the video signal reproduced by the magnetic heads 100 are displayed on the liquid crystal monitor 903 through the signal processing circuit 904 and output to an external device (not shown) through an interface section 905 . The audio signal reproduced by the magnetic heads 100 is output through a speaker (not shown).

According to the present invention, a video camera including a magnetic head which is satisfactory in the anti-corrosion characteristic and input and output characteristic and is durable against cracks is provided.

Specific Examples

Specific examples of the present invention will be described in detail.

Specific Example 1

The magnetic heads described in the first example having no metal magnetic thin film on the outer side surfaces, and the conventional magnetic heads 400 shown in FIGS. 9A through 9D having the metal magnetic thin film FM 2 on the outer side surfaces as a comparative example, were produced with the common specifications described below under the conditions shown in Table 1. The magnetic heads were evaluated for the recording and reproduction output, anti-corrosion characteristic, and ferrite cracking ratio.

TABLE 1
Condition	Evaluation
	Metal		Anti-corrosion
	magnetic	Shape of		characteristic
	Metal	thin film	winding	Recording/	(deterioration in output	Cracking
	magnetic	on side	window	reproduction	after spraying with	ratio
NO.		thin film	surfaces?	θ1	θ2	output	salt water)	(%)
1	&Asteriskpseud;	ba	Yes	45	45	56 dB	−6 dB	20
2	&Asteriskpseud;	ac	Yes	45	45	Δ	◯	35
3	&Asteriskpseud;	ae	Yes	45	45	◯	◯	25
4	&Asteriskpseud;	ag	Yes	45	45	◯	◯	30
5	&Asteriskpseud;	bb	No	45	45	Δ	Δ	0
6	&Asteriskpseud;	bc	No	45	45	X	X	0
7	&Asteriskpseud;	bd	No	45	45	Δ	Δ	0
8	&Asteriskpseud;	be	No	45	45	X	X	0
9	&Asteriskpseud;	bf	No	45	45	X	◯	0
10	&Asteriskpseud;	bg	No	45	45	X	◯	0
11		aa	No	45	45	◯	◯	0
12		ab	No	45	45	◯	◯	0
13		ac	No	45	45	◯	◯	0
14		ad	No	45	45	◯	⊚	0
15		ae	No	45	45	◯	⊚	0
16		af	No	45	45	◯	⊚	0
17		ag	No	45	45	◯	⊚	0
18		ac	No	60	60	◯	⊚	0
19		ad	No	60	60	◯	⊚	0
20		ac	No	45	90	⊚	⊚	0
21		ad	No	60	90	⊚	⊚	0
&Asteriskpseud;: comparative examples
⊚: Significantly superior to No.1
◯: Superior to No.1
Δ: Equivalent to No.1
X: Inferior to No.1

In Table 1, compositions of the metal magnetic thin films are indicated with aa through ag and ba through bg, which are shown in Table 2. In order to evaluate the anti-corrosion characteristic, salt water was sprayed on the samples. The recording and reproduction outputs before and after this test were compared. The anti-corrosion characteristic was evaluated by the degree of deterioration in the outputs. The ferrite cracking ratio was evaluated by the ratio of samples determined to be defective due to the ferrite cracking with respect to the total number of samples in each category.

In Table 1, the evaluation of the recording and reproduction output and the anti-corrosion characteristic and is shown with respect to the conventional magnetic head indicated by No. 1. “X” indicates inferiority as compared to the No. 1 magnetic head, “Δ” indicates equivalence to the No. 1 magnetic head, “◯” indicates superiority over the No. 1 magnetic head (i.e., superiority of more than 0 and less than +2 dB), and “⊚” indicates significant superiority over the No. 1 magnetic head (i.e., superiority of +2 dB or more).

The evaluation of the cracking ratio is shown with a percentage.

Each metal magnetic thin film contains magnetic crystalline particles. The magnetic crystalline particles can each have a generally needle-like shape, a generally column-like shape, or a multiple-branch shape (i.e., combination of the generally needle-like shape and the generally column-like shape).

	TABLE 2
	Composition of metal	dS	dL
	magnetic thin film wt %	nm	nm
Examples
	aa	(Fe 98 Si 0.5 Ta 1.5 ) 93 O 2 N 5	19	320
	ab	(Fe 98 Si 1.5 Ta 0.5 ) 93 O 2 N 5	21	330
	ac	(Fe 86 Si 10 Al 2 Ta 2 ) 93 O 2 N 5	18	280
	ad	(Fe 87.5 Si 9 Al 1.5 Ta 2 ) 93 N 7	22	340
	ae	(Fe 85 Si 10.5 Al 2.5 Ta 2 ) 91 N 9	15	150
	af	(Fe 76.5 Si 16 Al 7 Ta 0.5 ) 92 N 8	16	160
	ag	(Fe 83 Si 10 Al 2 Ta 5 ) 90 N 10	15	250
Comparative Examples
	ba	Fe 73 Si 18 Al 9	200	500
	bb	(Fe 98 Ta 2 ) 93 O 2 N 5	22	340
	bc	(Fe 98 Si 0.5 Ta 1.5 ) 93 O 2 N 5	200	480
	bd	(Fe 98 Si 2 ) 93 O 2 N 5	24	340
	be	(Fe 98 Si 1.5 Ta 0.5 ) 93 O 2 N 5	160	420
	bf	(Fe 70 Si 20 Al 7 Ta 3 ) 93 O 2 N 5	10	150
	bg	(Fe 86 Si 10 Al 2 Ta 2 ) 88 O 4 N 8	5	30

In Table 2, “dS” indicates the average length of a shorter side of the magnetic crystalline particles, and “dL” indicates the average length of a longer side of the magnetic crystalline particles. As shown in Table 2, dL exceeds 50 nm, and preferably is more than 60 nm and less than 5000 nm. dS is more than 5 nm and less than 60 nm.

Compositions aa through ag are represented by (M a X b Z c ) 100-d A d . M includes at least one magnetic metal element selected from the group consisting of Fe, Co and Ni. X includes at least on element selected from the group consisting of Si, Al, Ga and Ge. Z includes at least one element selected form the group consisting of elements of group IVa, elements of group Va and Cr. A includes at least one element selected from the group consisting of O and N.

a, b, c and d fulfill the relationships of:

about 0.1≦b≦about 26,

about 0.1≦c≦about 5,

a+b+c=100, and

about 1≦d≦about 10.

Compositions ac through ag are represented by (Fe a Si b Al c T d ) 100-e N e . T includes at least one element selected from the group consisting of Ti and Ta.

a, b, c, d and e fulfill the relationships of:

about 10≦b≦about 23,

about 0.1≦c≦about 5,

about 0.1≦c+d≦about 8,

a+b+c+d=100, and

about 1≦e≦about 10.

The common specifications mentioned above are as follows.

	Head:
	Track width:	17	μm
	Gap depth:	12.5	μm
	Gap length:	0.2	μm
	Number of turns:	16
	Metal magnetic thin film thickness:	4.5	μm
	Underlying layer: alumina; thickness:	2	nm
	C/N (carrier-to-noise ratio) characteristic:
	Relative speed of tape: 10.2	m/s
	Recording and reproduction frequency:	20.9	MHz
	Tape:	MP tape

Even when the structure in the magnetic heads in Table 1 (first example) was changed to the structure in the second example, the test results showed a similar tendency to that of Table 1.

Even when Si in Table 2 was changed to Ge, the test results showed a similar tendency to that of Table 1. Even when Si in compositions aa and ab in Table 2 was changed to Al, the test results showed a similar tendency to that of Table 1.

Even when Ta in Table 2 was changed to Ti, Zr, Hf, V, Nb or Cr, the test results showed a similar tendency to that of Table 1.

The expression “similar tendency” refers to that, for example, although the numerical values of the recording and reproduction output are not exactly the same, but the same evaluation, i.e., “X”, “Δ”, “◯” or “⊚” is obtained.

Based on the above-described experimental results, it was confirmed that the magnetic heads according to the present invention (indicated with No. 11 through No. 21) are improved in the recording and reproduction output, anti-corrosion characteristic and ferrite cracking ratio. The No. 14 through No. 21 magnetic heads were especially favorable in the anti-corrosion characteristic. The No. 20 and No. 21 magnetic heads having a winding window in which θ 12 =90° ( FIG. 3A ) were favorable in the recording and reproduction output.

The metal magnetic thin film includes a magnetic film containing, as a major material, magnetic crystalline particles. The magnetic crystalline particles of each composition mentioned above according to the present invention were observed to have a generally needle-like shape, a generally column-like shape, or a multiple-branch shape (i.e., combination of the generally needle-like shape and the generally column-like shape). An average volume Va and an average surface area Sa of the magnetic crystalline particles were confirmed to have the relationship of Sa>about 4.84 Va ⅔ .

Specific Example 2

The magnetic heads produced with the common specification described below under the conditions shown in Table 3 were evaluated in the same manner as in the specific example 1.

TABLE 3
Condition	Evaluation
	Metal	Metal	Record-	Anti-corrosion
	mag-	magnetic	ing/	characteristic	Crack-
	netic	thin film	repro-	(deterioration in output	ing
	thin	on side	duction	after spraying with	ratio
NO.		film	surfaces?	output	salt water)	(%)
51	&Asteriskpseud;	da	Yes	56 dB	−6 dB	20
52	&Asteriskpseud;	cc	Yes	◯	◯	37
53	&Asteriskpseud;	ce	Yes	◯	◯	30
54	&Asteriskpseud;	cg	Yes	◯	◯	30
55	&Asteriskpseud;	db	No	Δ	Δ	0
56	&Asteriskpseud;	dc	No	X	X	0
57	&Asteriskpseud;	dd	No	Δ	Δ	0
58	&Asteriskpseud;	de	No	X	X	0
59	&Asteriskpseud;	df	No	Δ	◯	0
60	&Asteriskpseud;	dg	No	X	◯	0
61		ca	No	◯	◯	0
62		cb	No	◯	◯	0
63		cc	No	◯	⊚	0
64		cd	No	◯	⊚	0
65		ce	No	◯	⊚	0
66		cf	No	◯	⊚	0
67		cg	No	◯	⊚	0
&Asteriskpseud;: comparative examples
⊚: Significantly superior to No.1
◯: Superior to No.1
Δ: Equivalent to No.1
X: Inferior to No.1

In Table 3, compositions of the metal magnetic thin films are indicated with ca through cg and da through dg, which are shown in Table 4.

In Table 3, the evaluation of the recording and reproduction output and the anti-corrosion characteristic and is shown with respect to the conventional magnetic head indicated by No. 1. “X” indicates inferiority as compared to the No. 1 magnetic head, “Δ” indicates equivalence to the No. 1 magnetic head, “◯” indicates superiority over the No. 1 magnetic head (i.e., superiority of more than 0 and less than +2 dB), and “⊚” indicates significant superiority over the No. 1 magnetic head (i.e., superiority of +2 dB or more).

The evaluation of the cracking ratio is shown with a percentage.

	TABLE 4
	Composition of metal	dS	dL
	magnetic thin film wt %	nm	nm
Examples
	ca	(Fe 98 Si 0.5 Al 0.5 Ti 1 ) 95 O 1 N 4	22	350
	cb	(Fe 98 Si 1.5 Al 0.2 Ti 0.3 ) 95 O 1 N 4	23	340
	cc	(Fe 86 Si 10 Al 2 Ti 2 ) 95 O 1 N 4	22	290
	cd	(Fe 87.5 Si 9 Al 1.5 Ti 2 ) 95 O 1 N 4	23	350
	ce	(Fe 85 Si 10.5 Al 2.5 Ti 2 ) 91 O 1 N 8	15	160
	cf	(Fe 76.5 Si 17 Al 3.5 Ti 3 ) 93 O 2 N 7	12	120
	cg	(Fe 83 Si 9 Al 3 Ti 5 ) 93 O 1 N 6	18	240
Comparative Examples
	da	Fe 73 Si 18 Al 9	200	500
	db	(Fe 98 Al 0.5 Ti 1.5 ) 95 O 1 N 4	22	340
	dc	(Fe 98 Si 0.5 Al 0.5 Ti 1 ) 95 O 1 N 4	220	490
	dd	(Fe 98 Si 2 ) 95 O 1 N 4	28	360
	de	(Fe 98 Si 1.5 Al 0.2 Ti 0.3 ) 95 O 1 N 4	180	480
	df	(Fe 70 Si 25 Al 2 Ti 3 ) 91 O 1 N 8	10	150
	dg	(Fe 86 Si 10 Al 2 Ti 2 ) 88 O 2 N 10	6	35

In Table 4, compositions ca through cg are represented by (M a X b Z c ) 100-d A d . M includes at least one magnetic metal element selected from the group consisting of Fe, Co and Ni. X includes at least one element selected from the group consisting of Si and Ge. Z includes at least one element selected from the group consisting of elements of group IVa, elements of group Va and Cr. A includes at least one element selected from the group consisting of O and N.

a, b, c and d fulfill the relationships of:

about 0.1≦b≦about 23,

about 0.1≦c≦about 8,

a+b+c=100, and

about 1≦d≦about 10.

Compositions cc and ce are represented by (Fe a Si b Al c Ti d ) 100-e-f N e O f , where a, b, c, d, e and f fulfill the relationships of about 10≦b≦about 13, about 1≦c≦about 3, about 1≦d≦about 3, a+b+c+d=100, about 4≦e+f≦about 10, and about 0.1≦f≦about 2.

The common specifications mentioned above are as follows.

	Head:
	Track width:	17	μm
	Gap depth:	12.5	μm
	Gap length:	0.2	μm
	Number of turns:	16
	Metal magnetic thin film thickness:	4.5	μm
	Underlying layer: alumina; thickness:	2	nm
	C/N characteristic:
	Relative speed of tape: 10.2	m/s
	Recording and reproduction frequency:	20.9	MHz
	Tape:	MP tape

Even when the structure in the magnetic heads in Table 3 (first example) was changed to the structure in the second example, the test results showed a similar tendency to that of Table 3.

Even when Si in Table 4 was changed to Ge, the test results showed a similar tendency to that of Table 3.

Even when Al and Ti in Table 4 were each changed to Ga, Zr, Hf, V, Ta, Nb or Cr, the test results showed a similar tendency to that of Table 3.

As in specific example 1, the expression “similar tendency” refers to that, for example, although the numerical values of the recording and reproduction output are not exactly the same, but the same evaluation, i.e., “X”, “Δ”, “◯” or “⊚” is obtained.

Based on the above-described experimental results, the effects of the present invention were confirmed.

The magnetic crystalline particles of each composition of the metal magnetic thin films were observed to have a generally needle-like shape, a generally column-like shape, or a multiple-branch shape (i.e., combination of the generally needle-like shape and the generally column-like shape). An average volume Va and an average surface area Sa of the magnetic crystalline particles were confirmed to have the relationship of Sa>about 4.84 Va ⅔ .

Specific Example 3

The magnetic heads in the first example were produced with the common specification described below under the conditions shown in Table 5, and evaluated for the recording and reproduction output and ripple.

TABLE 5
Condition	Evaluation
	Metal		Recording/
	magnetic	Underlying layer 2/	reproduction	Ripple
NO.	thin film	Underlying layer 1	output	dB
71	ac	No layer/no layer	54.5 dB	2.7
72	cc	No layer/no layer	54.2 dB	2.9
73	ac	No layer/Al 2 O 3 0.5 nm	◯	0.3
74	cc	No layer/Al 2 O 3 0.5 nm	◯	0.2
75	ac	No layer/Al 2 O 3 2 nm	◯	0.8
76	cc	No layer/Al 2 O 3 2 nm	◯	0.7
77	ac	No layer/Al 2 O 3 4 nm	◯	1.2
78	cc	No layer/Al 2 O 3 4 nm	◯	1.2
79	ac	No layer/Al 2 O 3 10 nm	Δ	2.4
80	cc	No layer/Al 2 O 3 10 nm	Δ	2.4
81	ac	Condition A 0.5 nm/Al 2 O 3	⊚	0.8
		2 nm
82	cc	Condition A 0.5 nm/Al 2 O 3	⊚	0.7
		2 nm
83	ac	Condition A 1.5 nm/Al 2 O 3	⊚	0.9
		2 nm
84	cc	Condition A 1.5 nm/Al 2 O 3	⊚	0.9
		2 nm
85	ac	Condition B 0.5 nm/Al 2 O 3	⊚	0.8
		2 nm
86	cc	Condition B 0.5 nm/Al 2 O 3	⊚	0.8
		2 nm
87	ac	Condition B 2 nm/Al 2 O 3	⊚	1.0
		2 nm
88	cc	Condition B 2 nm/Al 2 O 3	⊚	0.9
		2 nm

TABLE 6
Film formation conditions
					Average
	Film			Flow rate	particle
	formation	Power	Gas	of film	diameter
	method	density	pressure	forming gas	nm
Condition	RF	15 W/in 2	4 mTorr	Ar 75% +	2
A	magnetron			Nitrogen 25%
	sputtering
Condition	RF	15 W/in 2	4 mTorr	Ar 85% +	4
B	magnetron			Nitrogen 15%
	sputtering

In Table 5, compositions of the metal magnetic thin films are indicated with ac and cc, which are shown in Tables 2 and 4.

Also in Table 5, “underlying layer 1 ” refers to a layer in contact with the ferrite section (UL 1 in FIGS. 1 E and 4 E), and “underlying layer 2 ” refers to a layer in contact with metal magnetic film (UL 2 in FIGS. 1 E and 4 E).

Regarding the magnetic heads indicated with Nos. 73, 75, 77, 79, 81, 83, 85 and 87 in which the metal magnetic film has composition ac, the recording and reproduction output is evaluated with respect to the No. 71 magnetic head with neither underlying layer 1 nor 2 . “Δ” indicates equivalence to the No. 71 magnetic head, “◯” indicates superiority over the No. 71 magnetic head (i.e., superiority of more than 0 and less than +3 dB), and “⊚” indicates significant superiority over the No. 71 magnetic head (i.e., superiority of +3 dB or more).

The evaluation of the ripple is shown with a numerical value.

Table 6 shows the formation conditions of the underlying layer 2 in Table 5. As the target, and alloy target for a metal magnetic thin film was used.

The common specifications mentioned above are as follows.

	Head:
	Track width:	17	μm
	Gap depth:	12.5	μm
	Gap length:	0.2	μm
	Number of turns:	16
	Metal magnetic thin film thickness:	4.5	μm
	Underlying layer: alumina; thickness:	2	nm
	C/N characteristic:
	Relative speed of tape: 10.2	m/s
	Recording and reproduction frequency:	20.9	MHz
	Tape:	MP tape

Even when Al in Table 5 was changed to Si, the test results showed a similar tendency to that of Table 5. Even when nitrogen in Table 6 was changed into oxygen, the test results showed a similar tendency to that of Table 5. Even when compositions ac and cc in Table 5 were respectively changed to any of ca through cb and any of cd through cg, the test results showed a similar tendency to that of Table 5.

As in specific example 1, the expression “similar tendency” refers to that, for example, although the numerical values of the recording and reproduction output are not exactly the same but the same evaluation, i.e., “X”, “Δ”, “◯” or “⊚” is obtained.

Based on the above-described experimental results, the effects of the present invention were confirmed.

The magnetic crystalline particles of each composition of the metal magnetic thin films were observed to have a generally needle-like shape, a generally column-like shape, or a multiple-branch shape (i.e., combination of the generally needle-like shape and the generally column-like shape). An average volume Va and an average surface area Sa of the magnetic crystalline particles were confirmed to have the relationship of Sa>about 4.84 Va ⅔ .

As described above, the present invention provides a magnetic head which is satisfactory in the anti-corrosion characteristic and input and output characteristic and is sufficiently durable against cracking in a base, a method for producing the magnetic head, a video recording and reproduction apparatus including such a magnetic head, and a video camera including such a magnetic head.

The present invention also provides a magnetic head having an optimum combination of a metal magnetic thin film and a head structure.

Various other modifications will be apparent to and can be readily made by those skilled in the art without departing from the scope and spirit of this invention. Accordingly, it is not intended that the scope of the claims appended hereto be limited to the description as set forth herein, but rather that the claims be broadly construed.

Claims

1. A method for producing a magnetic head, the magnetic head including a pair of magnetic core halves, and a nonmagnetic layer provided between the pair of magnetic core halves for combining the pair of magnetic core halves,the method comprising: a step of forming a winding window in at least one of a pair of oxide magnetic plates which are generally flat; a step of forming at least one underlying layer on each of the pair of oxide magnetic plates; a step of forming a metal magnetic thin film on the underlying layer, the metal magnetic thin film being formed using a solid material containing an element which is a main component of the metal magnetic thin film in an atmosphere containing at least one of oxygen and nitrogen by a gas phase technique, wherein the metal magnetic thin film includes a magnetic film containing, as a major material, magnetic crystalline particles having an average volume Va and an average surface area Sa fulfilling the relationship of Sa>about 4.84 Va⅔ and the metal magnetic thin film has a composition represented by (MaXbZc)100-dAd, where M includes at least one magnetic metal element selected from the group consisting of Fe, Co and Ni, X includes at least one element selected from the group consisting of Si, Al, Ga and Ge, Z includes at least one element selected from the group consisting of elements of group IVa, elements of group Va, Al, Ga and Cr, and A includes at least one element selected from the group consisting of O and N, and a, b, c and d fulfill the relationships of about 0.1≦b≦about 26, about 0.1≦c≦about 5, a+b+c=100, and about 1≦d≦about 10; wherein the metal magnetic thin film includes magnetic crystalline particles, the magnetic crystalline particles have at least one shape selected from the group consisting of a generally needle-like shape, a generally column-like shape, and a multiple-branch shape combining the generally needle-like shape and the generally column-like shape, and the magnetic crystalline particles have an average length dS of a shorter side of about 5 nm<dS<about 60 nm and an average length of a longer side of about 60 nm<dL<about 5000 nm; a step of forming a groove in a body including the oxide magnetic plate, the underlying layer, and the metal magnetic thin film so that the groove has a width corresponding to a track; and a step of combining the body with another body including an oxide magnetic plate, an underlying layer, and a metal magnetic thin film, with the nonmagnetic layer interposed therebetween, wherein the pair of magnetic core halves each include an oxide magnetic base, at least one underlying layer provided on the oxide magnetic base, and a metal magnetic thin film provided between the underlying layer and the nonmagnetic layer, wherein at least one of the pair of magnetic core halves has a winding window therein, and wherein the metal magnetic thin film is provided in such a manner as to prevent the oxide magnetic base from cracking due to an internal stress generated in the metal magnetic thin film.

2. A method according to claim 1, wherein the steps are performed in the order of the winding window formation step, the underlying layer formation step, the metal magnetic thin film formation step, the track formation step, and then the combining step.

3. A method according to claim 1, wherein the steps are performed in the order of the underlying layer formation step, the metal magnetic thin film formation step, the winding window formation step, the track formation step, and then the combining step.

4. A method for producing a magnetic head, the magnetic head including a pair of magnetic core halves, and a nonmagnetic layer provided between the pair of magnetic core halves for combining the pair of magnetic core halves, the method comprising the steps of:forming a winding window in at least one of a pair of oxide magnetic plates which are generally flat; forming at least one underlying layer on each of the pair of oxide magnetic plates; forming a metal magnetic thin film on the underlying layer, the metal magnetic thin film being formed using a solid material containing an element which is a main component of the metal magnetic thin film in an atmosphere containing at least one of oxygen and nitrogen by a gas phase technique, the metal magnetic thin film containing, as a major material, magnetic crystalline particles having an average volume Va and an average surface area Sa fulfilling the relationship of Sa>about 4.84 Va⅔; forming a groove in a body including the oxide magnetic plate, the underlying layer, and the metal magnetic thin film so that the groove has a width corresponding to a track; and combining the body with another body including an oxide magnetic plate, an underlying layer, and a metal magnetic thin film, with the nonmagnetic layer interposed therebetween, wherein the metal magnetic thin film is provided in such a manner as to prevent the pair of oxide magnetic plates from cracking due to an internal stress generated in the metal magnetic thin film.

5. A method according to claim 4, wherein the steps are performed in the order of the winding window formation step, the underlying layer formation step, the metal magnetic thin film formation step, the track formation step, and then the combining step.

6. A method according to claim 4, wherein the steps are performed in the order of the underlying layer formation step, the metal magnetic thin film formation step, the winding window formation step, the track formation step, and then the combining step.

7. A method according to claim 4, wherein the metal magnetic thin film includes magnetic crystalline particles, which have an average length of a longer side of more that about 50 nm.

8. A method according to claim 7, wherein the magnetic crystalline particles have at least one shape selected form the group consisting of a generally needle-like shape, a generally column-like shape, and a multiple-branch shape including the magnetic crystalline particles of the generally needle-like shape and the generally column-like shape; and the magnetic crystalline particles having the generally needle-like shape and the generally column-like shape have an average length of a shorter side of more than about 5 nm and less than about 60 nm.

9. A method according to claim 7, wherein, where dS is an average length of a shorter side of the magnetic crystalline particles and dL is an average length of a longer side of the magnetic crystalline particles, about 5 nm<dS<about 60 nm and about 60 nm<dL<about 5000 nm.

10. A method according to claim 4, wherein the metal magnetic thin film has a composition represented by (MaXbZc)100-dAd, where M includes at least one magnetic metal element selected from the group consisting of Fe, Co and Ni; X includes at least one element selected form the group consisting of Si, Al, Ga and Ge; Z includes at least one element selected form the group consisting of elements of group IVa, elements of group Va, Al, Ga and Cr; A includes at least one element selected from the group consisting of O and N; and a, b, c and d fulfill the relationships of about 0.1≦b≦about 26, about 0.1≦c≦about 5, a+b+c=100, and about 1≦d≦about 10.

11. A method according to claim 10, wherein Z includes at least one element selected from the group consisting of elements of group IVa, elements of group Va and Cr.

12. A method according to claim 10, wherein X includes at least one element selected form the group consisting of Si and Ge; and a, b, c and d fulfill the relationships of about 0.1≦b≦about 23, about 0.1≦c≦about 8, a+b+c=100, and about 1≦d≦about 10.

13. A method according to claim 12, wherein the metal magnetic thin film has a composition represented by (FeaSibAlcTid)100-eNeOf where a, b, c, d, e and f fulfill the relationships of about 10≦b≦about 23, about 0.1≦d≦about 5, about 0.1≦c+d≦about 8, a+b+c+d=100, and about 1≦e+f≦about 10, and about 0.1≦f≦about 5.

14. A method according to claim 4, wherein the metal magnetic thin film has a composition represented by (FeaSibAlcTd)100-eNe where T includes at least one element selected from the group consisting of Ti and Ta; and a, b, c, d and e fulfill the relationships of about 10≦b≦about 23, about 0.1≦d≦about 5, about 0.1≦c+d≦about 8, a+b+c+d=100, and about 1≦e≦about 10.

15. A method according to claim 4, wherein the at least one underlying layer contains at least one of an oxide of Al, an oxide of Si, a nitride of Al, a nitride of Si, and a mixture thereof.

16. A method according to claim 15, wherein:the at least one underlying layer includes a first underlying layer in contact with the magnetic core half and a second underlying layer in contact with the metal magnetic thin film, the first underlying layer contains at least one of an oxide of Al, an oxide of Si, a nitride of Al, a nitride of Si, and a mixture thereof, the metal magnetic thin film contains at least one of oxygen and nitrogen; and the second underlying layer contains an element which is a main component of the metal magnetic thin film, and at least one of oxygen and nitrogen in a larger amount than the amount contained in the metal magnetic thin film, the second underlying layer contains crystalline particles, and the crystalline particles have an average particle diameter of about 5 nm or less at least in the vicinity of an interface between the first underlying layer and the second underlying layer.

17. A method according to claim 16, wherein:the first underlying layer contains an oxide of Al, and has a thickness of about 0.5 nm or more and about 4 nm or less; and the second underlying layer has a thickness of about 0.5 nm or more and about 200 nm or less.

18. A method according to claim 4, wherein the oxide magnetic plates contain a ferrite single crystal which includes and MnZn ferrite single crystal containing A mol % of Fe2O3, B mol % of MnO and C mol % of ZnO, where A, B and C fulfill the relationships of about 52≦A≦about 57, about 5≦B≦about 29, and about 16≦C≦about 21.

19. A method according to claim 4, wherein the metal magnetic thin film has a composition represented by (FeaSibAlcTid)100-eNeOf, where a, b, c, d, e and f fulfill the relationships of about 10≦b≦about 13, about 1≦d≦about 3, a+b+c+d=100, about 4≦e+f≦about 10, and about 0.1≦f≦about 2.