The present invention relates to a reproducing magnetic head and a magnetic recording apparatus utilizing the head, and more specifically, to highly sensitive magnetoresistive reproducing magnetic heads.
In recent years, a larger capacity recording apparatus is required for processing digital signals and increased quantities of information, and rapid progress in recording density has occurred in the development of magnetic recording apparatus such as a hard disk drive (HDD). Several years ago, inductive heads were used for both reading and writing. To increase storage capacity, bit size for recording to a magnetic recording medium (hereinafter, referred to as a recording medium or simply as a medium) was reduced and magnetic flux of a signal read from the recording medium was also reduced in size. However, inductive heads for reading a medium signal by using the electromagnetic inductive effect through a ring core of the related art could not sufficiently read the weak medium signals produced.
Accordingly, a magnetoresistive reproducing magnetic head (MR head) has been used. An MR head is capable of reading a medium signal because its resistance changes when magnetization of a magnetic thin film rotates in response to a magnetic field produced by a medium.
Among such MR heads, a gigantic magnetoresistive (GMR) head having a sensitivity of about two times the sensitivity of the magnetoresistive head of the related art has been widely used. The GMR head includes a laminated structure having a free-magnetic layer, a non-magnetic layer and a fixed magnetic layer, that is, a spin-valve type reproducing magnetic head.
However, recording apparatus having an even larger storage capacity is desired and such a large increase in recording density is required that a medium signal cannot be properly sensed even with a spin-valve type reproducing magnetic head. Accordingly, a tunnel type magnetoresistive reproducing magnetic head having still higher sensitivity, and a current perpendicular-to-the-plane (CPP) type magnetoresistive reproducing magnetic head for applying a current in the perpendicular direction of the film plane have been developed.
a)-1(c) show a spin-valve type magnetoresistive element of the related art.
Next,
In a case where a medium magnetic field 8 exists, the magnetizing direction of the free-magnetic layer 2 rotates in response to the medium magnetic field 8, as shown in
When the spin-valve type reproducing magnetic head and the tunnel magnetoresistive reproducing magnetic head of the related art are used, the fixed-magnetic layer 3 does not respond to the medium magnetic field and a medium signal can be read as a change of resistance through rotation of only a single soft-magnetic layer (free-magnetic layer 2).
However, when magnetizing directions of a pair of soft-magnetic layers 10 and 11 (
Meanwhile, in a case where the medium magnetic field 8 exists (vertically away from the plane 9 in
However, in the case where both end portions of the first free-magnetic layer and the second free-magnetic layer are fixed using a pair of anti-ferromagnetic layers of different blocking temperatures, a thickness of about 5 nm to 20 nm is required for the anti-ferromagnetic layers. Such a thickness of the anti-ferromagnetic layers creates a significant problem in realizing a narrow gap for high density recording.
Moreover, the regions of the bias applying layer arranged on both sides of the element suppress Barkhausen noise by applying a bias magnetic field to the free-magnetic layers. However, in this case, the result of such an arrangement is lower sensitivity of the free-magnetic layer to the medium magnetic field and reduction in reproducing output.
To read fine magnetic information recorded in a high density magnetic disk, the magnetoresistive element is also reduced in size.
Accordingly, it is desirable to provide a high sensitivity magnetoresistive reproducing magnetic head formed with a pair of free-magnetic layers in order to solve the problem explained above, and also to provide a magnetic recording apparatus utilizing the head. It is also desirable to provide a high sensitivity magnetoresistive reproducing magnetic head generally similar to the structures suffering from a reduction in output due to the bias applying layer, and also to provide a magnetic recording apparatus utilizing the head.
A reproducing magnetic head includes a first free-magnetic layer, a second free-magnetic layer, and a non-magnetic layer provided between the first free-magnetic layer and the second free-magnetic layer. Also included is a bias applying layer having a single region adjacent at least one of the first and second free magnetic layers for applying a bias magnetic field in the direction perpendicular to the medium facing plane of the first free-magnetic layer and the second free-magnetic layer, and an electrode electrically connected to the first free-magnetic layer, the second free-magnetic layer, and the non-magnetic layer. Magnetizations of the first free-magnetic layer and the second free-magnetic layer are tilted in opposite directions within a film plane of each free-magnetic layer from the direction perpendicular to the medium facing plane with a magnetic field generated when a current is applied to the first free-magnetic layer, the second free-magnetic layer, and the non-magnetic layer in the direction perpendicular to the medium facing plane.
In the structure explained above, magnetizing directions of the first free-magnetic layer and the second free-magnetic layer are opposed to each other, with a bias magnetic field from a single region of the bias applying layer and a magnetic field generated from the current tilted in the desired elevation angle from the medium facing plane. Moreover, a soft magnetic film usually generates a magnetic domain but magnetizations of the first free-magnetic layer and the second free-magnetic layer do not generate the magnetic domain due to the bias magnetic field from the bias applying layer.
Accordingly, a magnetizing direction of each free-magnetic layer responds to the medium magnetic field by rotating and becoming parallel or anti-parallel to such a medium magnetic field. Thereby, relative angles in magnetization of the first free-magnetic layer and the second free-magnetic layer are almost twice that of the reproducing magnetic head of the structure of the related art. As a result, the reproducing output obtained can be almost doubled.
Moreover, magnetizations of the first free-magnetic layer and the second free-magnetic layer are tilted in opposite directions by 30° to 60° in terms of an elevation angle for respective medium facing planes within the film plane of each free-magnetic layer. Therefore, an improved reproducing output can be obtained under the conditions explained above.
Moreover, the bias applying layer is electrically connected, on the side of the head opposite of the medium facing plane, with the first free-magnetic layer, second free-magnetic layer, and the non-magnetic layer. The bias applying layer also operates as an electrode. Since the bias applying layer is arranged on the side of the head away from the medium facing plane, reduction of output due to excessive control of the magnetic domain by the bias applying layer can be prevented with less control of the magnetic domain to each free-magnetic layer at the area near the medium facing plane, each free-magnetic layer having a larger sensitivity to the medium magnetic field.
The magnetic recording apparatus of the present invention includes a magnetic disk, and a reproducing magnetic head for reading recorded information from the disk. A flexible suspension is bonded to the reproducing magnetic head, and an actuator arm freely rotates the suspension. A detecting circuit device which is electrically connected to the reproducing magnetic head through an insulated wire on the suspension and the actuator arm detects an electrical signal read from the magnetic disk with the reproducing magnetic head. The magnetic recording apparatus utilizes the reproducing magnetic head of the present invention.
According to the magnetoresistive reproducing magnetic head of the present invention, a relatively high output can be obtained and a reproducing magnetic head suitable for high recording density and a large capacity magnetic recording apparatus can be provided.
The present invention will be explained with reference to the accompanying drawings.
a) is a side elevation view showing a structure of a conventional magnetoresistive element,
a)-2(c) are diagrams showing the magnetizing conditions of the free-magnetic layer and fixed-magnetic layer of a spin-valve type reproducing magnetic head of the related art.
a)-3(c) are schematic diagrams showing the magnetizing conditions of the first free-magnetic layer and second magnetic-layer of a reproducing magnetic head having a first free-magnetic layer and a second free-magnetic layer.
a) is a side elevation of the reproducing magnetic head of the first embodiment of the present invention observed from the direction parallel to the film plane.
b) is a cross-sectional view of the reproducing magnetic head of the first embodiment cut at the center of the element.
c) is a side elevation of the reproducing magnetic head of the first embodiment observed from the medium facing plane.
a)-6(b) are schematic diagrams showing the magnetizing conditions of the first free-magnetic layer and the second free-magnetic layer of the reproducing magnetic head of the first embodiment.
a)-9(b) are schematic diagrams showing the positional relationships of the medium suspension, slider, and reproducing magnetic head of the present invention, and structures of the reproducing magnetic head and write magnetic head, respectively.
a)-(c) show a structure of the first embodiment of a reproducing magnetic head of the present invention.
The reproducing magnetic head is formed, for example, by laminating a lower shielding layer of NiFe or the like and an insulating layer of Al2O3 or the like on the Al2O3-TiC substrate, sequentially laminating and processing into the predetermined shape CoFe of about 4 nm as a first free-magnetic layer 10, Cu of about 1.5 nm as a non-magnetic layer 5, CoFe of about 4 nm as a second free-magnetic layer 11, and arranging CoCrPt of about 15 nm in a single region 6c as a bias applying layer 6 for applying the bias magnetic field to the first free-magnetic layer and the second magnetic layer via the underlayer 7 formed of Cr of about 1.5 nm to the side of the plane d opposed to the medium facing plane 9 and Ti of about 80 nm as a current terminal 12 on the side of the medium facing plane c.
The bias applying layer 6 may be formed in a laminating structure of a ferromagnetic layer of CoPt or the like, anti-ferromagnetic layer of PdPtMn, IrMn or the like and a soft magnetic layer of NiFe, CoFe or the like. The layer 6 may also be arranged without the underlayer 7. Moreover, the current terminal 12 may also be formed of W or the like, while the first free-magnetic layer or the second free-magnetic layer may be formed of NiFe or the like and the non-magnetic layer may be formed of an insulating material such as Al2O3, MgO or the like. In addition, an underlayer of Ta or the like and a cap layer of Ta or the like are also provided in some cases.
The reproducing magnetic head of this embodiment allows the single region 6c of the bias applying layer 6 to operate as another current terminal. When no current is applied to the current terminal, the first free-magnetic layer 10 and the second free-magnetic layer 11 are respectively magnetized toward the direction perpendicular to the medium facing plane, due to the bias magnetic field from the bias applying layer 6, as shown in
Next, response to the medium magnetic field of magnetization of the reproducing magnetic head of the present invention will be explained.
When a medium magnetic field does not exist, magnetizing directions of the first free-magnetic layer 10 and the second free-magnetic layer 11 are opposed to each other with an angle of elevation of about 45° from the medium facing plane due to the magnetic field generated from the current and the bias magnetic field from the bias applying layer, as shown in
Next, when the medium magnetic field 8 is applied as shown in
In the related art of
When a tBr of the bias applying layer is reduced, the bias magnetic field applied to the free-magnetic layer becomes small, and the rotating angle of the free-magnetic layer corresponding to the medium magnetic field becomes larger. However, control of the magnetic domain of the free-magnetic layer is also reduced, resulting in a possible generation of Barkhausen noise. When Barkhausen noise is generated, an asymmetrical property of the reproducing waveform or output becomes larger. This asymmetrical property is preferably set within ±5%. When the asymmetrical property is set to ±5% from
Here, a reproducing output of the reproducing magnetic head is expressed with the following formula (1).
V=(1/2)×ΔR×(1−cos θ)×Is (1)
Here, V is a reproducing output, ΔR is change in the magnetic resistance, θ is a relative angle between the first free-magnetic layer and the second free-magnetic layer, and Is is a sense current. From the description herein, it is desirable that the magnetizing direction of the first free-magnetic layer and the second free-magnetic layer is rotating at an angle equal to 30° or less for the medium magnetic field. As a result, if the medium magnetic field does not exist, excellent reproducing output can be obtained through magnetization of the first free-magnetic layer 10 and the second free-magnetic layer 11 by setting the angle of elevation with respect to the medium facing plane c to an angular range of 30° to 60°. The reason for this setting is that when the angle of elevation with respect to the medium facing plane c is set to 30° or less, the first free-magnetic layer and the second free-magnetic layer are anti-parallel with the medium magnetic field. Meanwhile, when the angle of elevation with respect to the medium facing plane c is set to 60° or more, the first free-magnetic layer and the second free-magnetic layer become parallel with the medium magnetic field and a linear reproducing output can no longer be obtained.
Moreover, in the related art, rotation of the magnetizing direction of the free-magnetic layer 2 at both ends of the element is reduced because the magnetic field from the dual regions 6a, 6b of the bias applying layer 6 is applied at both ends of the element, as shown in
In this embodiment, magnetization of the first free-magnetic layer and the second free-magnetic layer is conducted without any influence thereon due to the element core width direction. Therefore, a large anti-magnetic field is not generated and significant Barkhausen noise is not generated even though the bias applying layer does not have regions on both end portions of the element.
Here, a magnetic recording apparatus loading the reproducing magnetic head of this embodiment will be explained briefly.
The housing 21 accommodates a fixed detecting circuit device for detecting the recording/reproducing signals. The detecting circuit device detects changes in the resistance value of the magnetoresistive element and recovers information from the medium by feeding a sense current to the magnetoresistive element of the reproducing magnetic head and measuring changes in voltage across the magnetoresistive element.
a) is a schematic diagram showing the positional relationship between the suspension 18, slider 22 of
b) shows a reproducing magnetic head and a write magnetic head of the embodiment shown in
When the medium magnetic field produced by the magnetic disk 16 in accordance with the recorded magnetic information is applied to the reproducing magnetic head 24 of this embodiment, which is held between the lower shield 23 and the upper shield 25, magnetizing directions of the first free-magnetic layer and the second free-magnetic layer respectively rotate independently as shown in
The present invention is not limited to the specifically disclosed embodiments, and variations and modifications may be made without departing from the scope of the present invention.
Number | Date | Country | Kind |
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2006-310731 | Nov 2006 | JP | national |