The best mode for carrying out the invention is now explained in greater details.
Before the structure of the thin-film magnetic head of the invention is explained, an account is given of the patterned media that is the subject for magnetic recording in the invention.
As shown in
The recording tracks (TR) shown in
The minimum magnetization inversion units 310 are lined up at equal intervals in the lengthwise direction of the recording tracks (indicated by an action arrow TRL) and in the widthwise direction of the recording tracks (indicated by an action arrow TRW). The lengthwise direction (indicated by the action arrow TRL) is the direction of travel of the head.
The position of the minimum magnetization inversion unit 310 located at a track adjacent to a specific track is determined substantially at center of the minimum magnetization inversion unit 310 adjacent to that specific track in the lengthwise direction of the recording tracks.
Each minimum magnetization inversion unit 310 that is a recording bit is formed of a magnetic material area; for instance, it is formed of a magnetic material capable of perpendicular magnetic recording on the film plane. The depthwise lower portion of the magnetic material area taking aim at such perpendicular recording may be provided with a lining layer made of a soft magnetic material.
For the nonmagnetic material for the nonmagnetic area 350, for instance, use may be made of an oxide such as SiO2, Al2O3 and TiO2; a nitride such as Si3N4, AlN and TiN; a carbide such as TiC; and a boride such as BN.
It is here noted that the minimum magnetization inversion unit 310 that is a recording bit and the nonmagnetic area 350, for instance, are formed on a disk-form substrate, and the recording tracks provided by an array of minimum magnetization inversion units 310 are preferably formed on concentric circles. It is also noted that the minimum magnetization inversion unit 310 is by far smaller than disk size: its planar shape is not particularly limited, although its preferable shape, for instance, is a circular or rectangular shape as shown.
Such a patterned media may be fabricated by, for instance, two methods: (1) a magnetic material is filled in previously prepared mesopores (multipores) of about 2 to 50 nm, and (2) patterning is carried out after (or before) the formation of a magnetic film to form a given pattern. Specifically, the aforesaid method (1) involves block copolymer phase separation, guided self-assembly, Langmuir-Blodgett method, alumina anodic oxidization method, micelle method or the like, and the aforesaid method (2) involves optical lithography, electron beam lithography, X-ray lithography, interference lithography, nanoimprint or the like.
In this regard, synchronism with such a patterned media may be established by previously determining the plane density (track density) of each zone-sector in the media and then patterning the media. Patterning may be carried out by a physical method such as stamping or etching, or chemical method.
One exemplary construction of the whole thin-film magnetic head according to the invention is now explained with reference to
Certain terminology may be used in the following description for convenience in reference only. For instance, the word “width” would refer to a dimension in the X-axis direction shown in
The thin-film magnetic head is used on a magnetic recording system such as a hard disk drive for the purpose of applying magnetic processing to a recording medium moving in the medium travel direction M.
For instance, the thin-film magnetic head illustrated in the drawings is a composite type head capable of implementing both recording and reproducing as magnetic processing. The structure comprises, as shown in
For instance, the reproducing head portion 100A has a multilayer structure comprising a lower read shield layer 3, a shield gap film 4 and an upper read shield layer 30 stacked one upon another in that order. In the shield gap layer 4, there is a magneto-resistive effect device (MR device) 8 embedded as a reproducing device in such a way that its one end face is exposed on the recording medium opposite plane (air bearing surface) 70 in opposition to the recording medium.
Both the lower 3 and the upper read shield layer 30 are provided to separate the MR device magnetically from the surroundings, extending rearward from the air bearing surface 70. The lower read shield layer 3 is made of a soft magnetic material such as permalloy (Ni (80 wt %) Fe (20 wt %)) that is a nickel-iron alloy, and has a thickness of about 0.5 to 2.0 μm.
In the embodiment here, the upper read shield layer 30 has a structure in which a nonmagnetic layer 6 is sandwiched between two upper read shield portions 5 and 7. In other words, that upper read shield layer 30 has a structure where the upper read shield portion 5, the nonmagnetic layer 6 and the upper read shield portion 7 are stacked one upon another in order from a side near to a shield gap film 4.
The upper read shield portion 5 is made of a magnetic material such as permalloy, and has a thickness of typically about 0.5 to 2.0 μm. The upper read shield portion 7 is made of a magnetic material such as permalloy, too, and has a thickness of typically about 0.3 to 1.5 μm. The nonmagnetic layer 6 is made of a nonmagnetic material such as ruthenium (Ru) or alumina, and has a thickness of typically about 0.1 to 0.2 μm. While it is shown and described that the upper read shield layer 30 has a multilayer structure, it is contemplated that it is not always required to have a multilayer structure; it could have a single-layer structure as is the case with the lower read shield layer 3.
The shield gap film 4 is provided to separate the MR device 8 electrically from the surroundings; for instance, it is made of a nonmagnetic material such as alumina.
The MR device operates in such a way as to implement reproducing processing by making use of typically the giant magneto-resistive (GMR) effect, the TMR effect or the like.
The recording head portion 100B, for instance, has a multilayer structure comprising a first-stage thin-film coil 10 buried around with insulating layers 11, 12, 13, a nonmagnetic layer 14, a magnetic pole layer 40 partially buried around with an insulating layer 16, a gap layer 17, a second-stage thin-film coil 22 buried with an insulating layer 50 that forms a magnetic coupling opening (back gap 50BG) and a write shield layer 60, all stacked one upon another in order.
In
The thin-film coil 10 has a primary function of generating a leakage-preventive magnetic flux for holding back leakage of a recording magnetic flux produced at the thin-film coil 22. This thin-film coil 10 is made of a highly electroconductive material such as copper, and has a thickness of typically about 2.0 μm.
As typically shown in
The insulating layers 11, 12, 13 are formed in such a way as to separate the thin-film coil 10 electrically from the surroundings. The insulating layer 11 is formed in such a way as to be filled up between the turns of the thin-film coil 10 and provide a cover around the thin-film coil 10. This insulating layer 11 is made of a non-magnetic insulating material such as a photoresist or spin-on-glass (SOG) exhibiting fluidity upon heating, and has a thickness of typically about 2.0 μm.
In the embodiment here, the insulating layer 11 is formed in such a way as to cover only the sides of the thin-film coil 10 but provide no cover to the upper side of the thin-film coil 10, as shown in
The insulating layer 12 is formed in such a way as to provide a cover around the insulating layer 11. This insulating layer 12 is made of a nonmagnetic material such as alumina, and has a thickness of typically about 2.0 μm.
The insulating layer 13 is formed in such a way as to give a cover to the thin-film coil 10 as well as the insulating layers 11, 12. This insulating layer 13 is made of a nonmagnetic material such as alumina, and has a thickness of typically about 0.2 μm.
The nonmagnetic layer 14 is formed of a nonmagnetic insulating material such as alumina, or a nonmagnetic electroconductive material such as ruthenium, and has a thickness of typically about 1.0 μm.
The magnetic pole layer 40 has a primary function of implementing recording processing by receiving a magnetic recording magnetic flux produced at the thin-film coil 22 and releasing that magnetic flux toward the minimum magnetization inversion units (recording bit units) of the patterned media, thereby inverting the direction of magnetization of the minimum magnetization inversion units.
Such magnetic pole layer 40 is located on the leading side of the thin-film coil 22, extending rearward from the air bearing surface 70, more specifically, as far as the back gap 50BG. It is noted that when the state of movement of the patterned media that moves toward the patterned medium travel direction M shown in
In the embodiment here, the magnetic pole layer 40 has a structure where, as shown in
The main magnetic pole layer 15 functions as a portion for releasing off a main writing magnetic flux. This main magnetic pole layer 15 extends rearward from the air bearing surface 70 on the leading side, more specifically, as far as the back gap 50BG, and has a thickness of typically about 0.25 μm. Such main magnetic pole layer 15, for instance, is made of an iron alloy or the like. The iron alloy here, for instance, includes an iron-nickel alloy (FeNi), an iron-cobalt alloy (FeCo) or an iron-cobalt-nickel alloy (FeCoNi), all rich in iron (Fe).
It is noted that the aforesaid “coupled” would mean just only a coupling involving physical contact but also a coupling involving physical contact plus a magnetically conductive coupling.
As shown in
The front end 15A is primarily adapted to substantially release a recording magnetic flux produced at the thin-film coil 22 toward the patterned media, and has an exposed surface 15M exposed on the air bearing surface 70, as shown in
The trailing edge TE of the front end 15A provides a substantial recording site of the magnetic pole layer 40. Regarding the planar shape of the exposed surface 15M here, it is noted that the angle θ between the extending direction of the lower end edge E2 and the side end edges E3 could be set without restriction typically in the range of less than 90°.
The rear end 15B shown in
The auxiliary magnetic pole layer 19 functions as a portion adapted to receive a dominant magnetic flux. Typically, this auxiliary magnetic pole layer 19 extends rearward from a position P1 (the first position) receded from the air bearing surface 70. To be more specific, it extends as far as the rear of the main magnetic pole layer 15 at the back gap 50BG, and has a thickness of typically about 0.45 μm. Preferably, the auxiliary magnetic pole layer 19 is made of an iron-cobalt-nickel alloy. Note here that the auxiliary magnetic pole layer 19 may just as well be located on the lower portion of the main magnetic pole layer 15 (on the leading side).
As shown typically in
The insulating layer 16 is provided to isolate the main magnetic pole layer 15 electrically from the surroundings. This insulating layer 16 is made of a nonmagnetic insulating material such as alumina, and has a thickness of typically about 0.25 μm.
The gap layer 17 is formed in such a way as to provide a gap for the magnetic separation of the magnetic layer 40 from the write shield layer 60. As typically shown in
The insulating layer 50 defines the throat height TH that is one of important determinants for the recording performance of the thin-film magnetic head, and is adapted to cover the thin-film coil 22 in such a way as to isolate it electrically from the surroundings. As shown in
As shown in
The aforesaid “position P2” is corresponding to the foremost end position of the insulating layer 50 (nearest to the air bearing surface 70). That is, there is a “zero throat height position TP” for defining the throat height TH. That throat height TH is a distance between the air bearing surface 70 and the zero throat height position TP. This auxiliary insulating layer 20 is made of a nonmagnetic insulating material such as alumina. In the embodiment shown in
As shown in
The main insulating layer portion 21A is made of a nonmagnetic material such as alumina, and has a thickness of typically about 0.2 μm.
The main insulating layer portion 21B is made of a nonmagnetic insulating material such as a photoresist or spin-on-glass (SOG) that exhibits fluidity upon heating. A portion of this main insulating layer portion 21B at and near its end edge is in such a rounded slant shape as to fall away toward that end edge.
The thin-film coil 22 is formed for the generation of a recording magnetic flux. For instance, the thin-film coil 22 operates such that currents flow in the direction opposite to the direction taken by currents through the aforesaid thin-film coil 10.
The write shield layer 60 works capturing the spreading component of a recording magnetic flux released off the magnetic pole layer 40, thereby holding back the spreading of that magnetic flux. Further, the structure of the write shield layer 60 provides one of effective means capable of controlling the combined release angle Φ for the main recording magnetic field that is generated from the magnetic pole layer 40—part of the invention as described later—toward the patterned media for the purpose of recording magnetic information.
Located on the trailing side of the main magnetic pole layer 40 and thin-film coil 22, the write shield layer 60 extends rearward from the air bearing surface 70, whereby it is spaced by the gap film 17 away from the magnetic pole layer 20 on its side near to the air bearing surface 70, and linked to the magnetic layer 40 through the back gap 50BG in its side far away from the air bearing surface 70.
The write shield layer 60 here comprises the TH defining layer 18 (the first magnetic shield layer portion) and a yoke layer 23 (the second magnetic shield layer portion) that are separate from each other, and has a structure wherein the TH defining layer 18 and yoke layer 23 are coupled to each other. It is here noted that the write shield layer 60 is not limited to the couple structure as shown; it may be an integral structure.
The TH defining layer 18 functions as a dominant magnetic flux inlet port adapted to capture an extra portion of the magnetic flux released directly from the magnetic pole, and has a function as well of controlling the combined release angle Φ for the main recording magnetic field that is generated from the magnetic pole layer 40 toward the patterned media for the purpose of recording magnetic information.
As shown typically in
The TH defining layer 18 is made of a magnetic material having a high saturation flux density such as FeNi, FeCo and FeCoNi alloys, and assumes on a rectangular planar shape where W3>W2, preferably W3>W1, as shown in
The yoke layer 23 is set up in such a way as to function as a passage for the magnetic flux captured out of the TH defining layer 18. As shown typically in
In the embodiment here, for instance, the yoke layer 23 extends as far as the rear of the back gap 50BG while linked to the main magnetic pole layer 40 at the back gap 50BG. Such yoke layer 23, for instance, is made of a magnetic material similar to that of which the TH defining layer 18 is made, and takes a rectangular planar shape having a width W3 as shown in
The distance of the main insulating layer 21 receded from the air bearing surface 70, viz., a distance L3 between the air bearing surface 70 and the position P3 is greater than the length of the TH defining layer 18, viz., a distance L2 between the air bearing surface 70 and the position P2 (L3>L2). In consideration of the structural relation where the distance L3 is greater than the distance L2, the write shield layer 60 is designed such that the length of a portion of the yoke layer 23 adjacent to the TH defining layer 18 (viz., the distance L3) is greater than the length of the TH defining layer (viz., the distance L2). In other words, when the magnetic flux is captured in the yoke layer 23 of the write shield layer 60 via the TH defining layer 18, the magnetic path taken by that magnetic flux flowing through the write shield layer 60 is incrementally expanded.
It is here noted that the thin-film magnetic head as described above may have a light source for so-called thermal assist recording purposes mounted on it. It is also noted that the thin-film magnetic head as described above may have shields mounted just only on the trailing side of the magnetic pole but on both its sides as well.
Part of the invention to be specifically and structurally claimed by the invention in the preferable whole construction of the thin-film magnetic head as described above is now explained in further details with reference to
Corresponding to
Corresponding to
As shown in
As that combined release angle Φ for the dominant recording magnetic field goes below 35°, it causes the inconvenience of being only imperfect inversion of magnetization of the minimum magnetization inversion units for the reason that the angle of access to the patterned media surface is too shallow for the saturation of magnetization of the minimum magnetization inversion units. In a word, there is only too insufficient recording or storage of magnetic information. As 65° is exceeded, on the other hand, it takes much time for the inversion of magnetization, so that faster switching operation—the object of the invention—is not achievable. The method of making the magnetization inversion speed (time) of the minimum magnetization inversion units much faster (shorter) by virtue of an oblique magnetic field in the aforesaid angle range of 35° to 65° is strictly based on the merit obtained through the use of the patterned media as a recording medium. In other words, even when it is attempted to record magnetic information on a medium in contrast to the patterned media, viz., a non-patterned magnetic recording film available in the form of an ordinary continuously formed film, in the aforesaid angle range of 35° to 65° for the combined release angle Φ for the dominant recording magnetic field, there is no way to overwrite. This is because for a continuous film having a structure different from that of the patterned media, the combined release angle for the dominant recording magnetic field must exceed 65°.
Here the exchange coupling of magnetic particles is elaborated on. In a continuous medium, there is an exchange coupling occurring between adjacent bits; however, in the patterned media in contrast to the continuous medium, there would be substantially no or little exchange coupling, because bits are physically isolated from one another. In case there is an exchange coupling, that coupling would be extremely weak. With the patterned media where a magnetic flux can penetrate from between patterns, therefore, there is switching more easily occurring than would be possible with a continuous medium having an increased exchange coupling.
The “combined release angle Φ for the dominant recording magnetic field” referred to in the present disclosure is defined as a combined magnetic field angle of a component in the perpendicular direction (tantamount to the Y direction in
Such a combined release angle Φ for the dominant recording magnetic field may be adjusted by adjusting the thickness TH of the TH defining layer 18 that works capturing the spreading component of a recording magnetic flux released off the main magnetic pole layer 15, thereby holding back the spreading of that magnetic flux (
The head gimbal assembly and hard disk system according to the embodiment here are now explained.
A slider 210 included in the head gimbal assembly is first explained with reference to
The substrate 211 is in a generally hexahedral shape. Of the six surfaces of the substrate 211, one surface (the upper surface in
As the hard disk rotates in the γ direction in FIG. 6, it causes an air flow passing between the hard disk and the slider 210 to induce lift relative to the slider 210 in the downward β direction in
Near the end of the slider 210 on an air exit side (the left lower end in
A head gimbal assembly 220 according to this embodiment is now explained with reference to
The base plate 224 is adapted to be attached to an arm 230 of an actuator for moving the slider 210 in the track traverse direction a of the hard disk 262. The actuator comprises the arm 230 and a voice coil motor for driving that arm 230. At a portion of the flexure 223 having the slider 210 attached to it, there is a gimbal portion provided for keeping the posture of the slider 210 constant.
The head gimbal assembly 220 is attached to the arm 230 of the actuator. The head gimbal assembly 220 attached to one arm 230 is called a head arm assembly, whereas the head gimbal assembly 220 attached to a carriage at its plurality of arms is referred to as a head stack assembly.
One each example of the head stack assembly and the hard disk system according to the embodiment here are now explained with reference to
A head stack assembly 250 comprises a carriage 251 having a plurality of arms 252. The plurality of arms 252 are provided with a plurality of the head gimbal assemblies 220 such that they line up perpendicularly at an interval. On the side of the carriage 251 that faces away from the arms 252, there is a coil 253 attached, which coil becomes a part of the voice coil motor. The head stack assembly 250 is incorporated in the hard disk system.
The hard disk system comprises a plurality of hard disks 262 attached to a spindle motor 261. For each hard disk 262, two sliders 210 are located such that they are opposite to each other with the hard disk 262 held between them. The voice coil motor has also permanent magnets 263 located at opposite positions with the coil 253 of the head stack assembly 250 held between them.
The head stack assembly 250 except the slider 210 and the actuator correspond to the positioning device here which is operable to support the slider 210 and position it relative to the hard disk 262.
With the hard disk system here, the actuator is actuated to move the slider 210 in the track traverse direction of the hard disk 262, thereby positioning the slider 210 with respect to the hard disk 262. The thin-film magnetic head incorporated in the slider 210 works such that information is recorded by a recording head in the hard disk 262, and the information recorded in the hard disk 262 is played back by a reproducing head.
The head gimbal assembly and the magnetic disk system here have pretty much the same action as the thin-film magnetic head according to the foregoing embodiment.
While the embodiment here has been described with reference to the thin-film magnetic head of the structure wherein the reproducing head is located on the substrate side and the recording head is stacked on the reproducing head, it is contemplated that that order of stacking could be reversed. When the thin-film magnetic head here is used as a read-only head, the recording head could be removed from it.
The construction and advantages of the thin-film magnetic head according to the invention are now explained in greater details with reference to specific examples of experimentation.
The thin-film magnetic heads having such structure as shown in
There were various thin-film magnetic head samples prepared, wherein the write shield layer 60 was made of CO65Ni25Fe15, the thickness TH of the TH defining layer 18 of the write shield layer 60 as shown in
For reference purposes,
The patterned media used for experimental recording had the following specifications.
The track width, bit length and thickness were 60 nm, 60 nm and 30 nm, respectively. The material for the magnetic layer was FePt (Al2O3 matrix), with a coercive force of 8,000 Oe and a saturation magnetization of 700 emu/cc. The then soft magnetic under layer was CoZrTa of 100 nm in thickness.
For such a patterned media, the magnetization transition time (magnetization inversion time: switching time in arbitrary unit) for each dot was found on the thin-film magnetic heads whose combined release angle Φ for the dominant recording magnetic field was 90°, 72°, 65°, 55°, 45°, 40°, 35° and 27°, respectively. For the relative estimation of the respective data, the values of the data worked out by standardization with the arbitrary unit value of 90° as a reference are set out in the table.
The magnetization transition time for each bit was determined by measuring a time length from the start of inversion of magnetization of the bit after the release of the recording magnetic field to a point at which the magnetization of the bit reached a maximum in the inversion direction.
The results are shown in Table 1.
There was experimentation carried out, wherein in each sample of TH=100 nm prepared in Experimental Example I, the specifications of the write shield layer were modified as shown in
The results are shown in the graph of
As can be seen from the graph of
There was comparative experimentation done as follows. This was to show that the effect of the invention of this application wherein the combined release angle for the dominant recording magnetic field was set at Φ=35° to 65° was quite unique to the patterned media having physically isolated bits. More specifically, experimentation for overwrite performance was done with a generally available continuous medium of the perpendicular magnetic recording mode.
The specifications of the continuous medium of the perpendicular magnetic recording mode were: a recording layer made of CoCrPt.SiO2, a coercive force of 5,200 Oe, a saturation magnetization of 500 emu/cc, and a soft magnetic lining layer having a multilayer structure of CoZrTa (25 nm)/Ru (0.8 nm)/CoZrTa (25 nm).
In the magnetic heads used here, the respective combined release angles Φ for the dominant recording magnetic field were 90°, 72°, 65°, 58°, 55°, 50°, 45°, 40°, 35°, and 27°.
Overwrite performance was determined by recording LF (12 MHZ) on HF (90 MHz) and measuring the output ratio (dB) between the output of HF before recording and the rest of HF after LF recording.
For comparative consideration, overwrite performance was determined for the aforesaid patterned media too.
The results are set out in Table 2 give just below.
From the results of Table 2, it can be appreciated that between the patterned media and the continuous medium, there are differences in the combined release angle Φ for the dominant recording magnetic field for achieving satisfactory overwrite values.
The advantages of the invention would be understood from the aforesaid results of experimentation. That is, in the invention, the combined release angle Φ for the dominant recording magnetic field generated from the magnetic pole layer toward the patterned media for the purpose of recording magnetic information is set to within the angle range of 35° to 65° with respect to the patterned media surface. It is thus possible to invert, with efficiency and reliability, the direction of magnetization of the bits of the patterned media having physically isolated bits. In addition, the setting of the combined release angle for the dominant recording magnetic field to Φ=35° to 65° is a quite unique requirement that is effective for the patterned media alone.
Number | Date | Country | Kind |
---|---|---|---|
2006-154658 | Jun 2006 | JP | national |