JP3825418B2 - Magnetic disk unit - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to a magnetic disk apparatus with improved reproduction signal reliability.
[0002]
In recent years, the amount of information recorded in a magnetic disk device or the like has increased due to an increase in the amount of information processing in a computer system, and a smaller, larger capacity has been promoted, a higher recording density is required, and a high-performance magnetic disk device Is needed.
[0003]
[Prior art]
FIG. 24 is a cross-sectional view schematically showing a main part of a conventional magnetic disk device.
[0004]
In this figure, reference numeral 11 denotes a magnetic recording film 14 made of a CoCr film having magnetic anisotropy in the in-plane direction on a nonmagnetic substrate 12 made of an aluminum plate subjected to surface treatment by NiP plating with a Cr underlayer film 13 interposed therebetween. It is a laminated magnetic disk.
[0005]
21 is a slider, Al ₂ O _Three A first magnetic pole 23 made of a NiFe alloy film on a nonmagnetic substrate 22 made of, etc., and a second magnetic pole 26 made of a NiFe alloy film via a coil 25 encapsulated by an interlayer insulating film 24 on the first magnetic pole 23. However, each front end is exposed to the disk facing surface, and their rear end portions are arranged in a magnetically connected state. ₂ O _Three There is a ring magnetic pole induction type thin film magnetic head coated with a protective film 27 such as a film, and there is a structure in which the magnetic disk 11 and the thin film magnetic head 21 are combined.
[0006]
The first and second magnetic poles 23 and 26 are magnetized by causing a recording signal current to flow through the coil 25 of the thin-film magnetic head 21, and the magnetic disk 11 is caused by the magnetic flux leaking from the gap between the tips of both magnetic poles. Magnetic recording of information is performed on the magnetic recording film 14.
[0007]
Further, the magnetic flux leaking from the magnetic recording film 14 of the magnetic disk 11 on which information has already been recorded flows into the first and second magnetic poles 23 and 26 of the thin film magnetic head 21 and is magnetized, and according to the change of the magnetic flux. Information is reproduced by detecting a voltage generated in the coil 25 as a reproduction signal.
[0008]
In order to increase the recording / reproducing efficiency with such a thin film magnetic head 21, it is necessary to use a magnetic film having excellent soft magnetic characteristics as the magnetic film constituting the first and second magnetic poles 23 and 26.
[0009]
Further, in recent years, attention has been focused on a read-only magnetoresistive thin film head (hereinafter abbreviated as an MR head) that can obtain a large reproduction output without depending on the rotational speed of the magnetic disk. A composite thin film magnetic head in which an inductive thin film magnetic head is integrally formed has been proposed.
[0010]
FIG. 25 is an explanatory diagram when a conventional composite thin film magnetic head is used. 25A is a cut slope view, and FIG. 25B is a cross-sectional view. FIG. 26 shows a bottom view of FIG.
[0011]
FIGS. 25A, 25B, and 26 show a composite thin film magnetic head 30 of an electromagnetic conversion head (recording head) and a magnetoresistive effect type (MR) head (reproducing head). A resistance effect type head (MR head) 31 includes a rectangular magnetoresistive effect element (MR element) 33 formed on a nonmagnetic substrate 32 and a lead conductor layer 34 of the MR element 33. _a , 34 _b (Described later), the upper and lower magnetic shield layers 35 _a , 35 _b It consists of and.
[0012]
Leader conductor layer 34 _a , 34 _b Are cut at a predetermined width with respect to the longitudinal direction of the MR element 33 and connected to both ends of an MR layer (described later) of the MR element 33. MR element 33 and lead conductor layer 34 _a , 34 _b Is the upper magnetic shield layer 35 _a And lower magnetic shield layer 35 _b And electrically connected by a non-magnetic insulating layer 36.
[0013]
On the other hand, an electromagnetic conversion head (inductive head) 37 for recording information on the magnetic disk 11 is an upper magnetic shield element 35 of the MR head 31. _a Is the lower magnetic pole (first magnetic pole), and alumina (Al ₂ O _Three The interlayer insulating layer 39 made of thermosetting resin, the thin-film coil conductor layer (Cu) 40, and the upper magnetic pole 41 are laminated through the recording gap 38 with the upper magnetic pole ()) and the lower magnetic pole (second magnetic pole) 41 and the lower magnetic pole (upper magnetic) Shield layer) 35 _a The information is horizontally recorded by the recording gap 38 formed in the above. A protective insulating layer 42 is formed on the upper magnetic pole 41.
[0014]
Here, FIG. 27 shows a cross-sectional view of a conventional MR element and a lead conductor layer. The MR element 33 includes a soft magnetic layer 33 serving as a linearization bias layer. _a For example, the soft magnetic layer 33 is made of NiFeCr SAL (Soft Adjacent Layer) with a thickness of 300 mm. _a Nonmagnetic intermediate layer (for example, tantalum with a thickness of 100 mm) 33 _b MR layer 33 via _c For example, it is formed of NiFe with a thickness of 300 mm.
[0015]
MR layer 33 _c On the upper side, one lead conductor layer (FeMn (manganese) layer 34) is formed so as to form, for example, an interval of 4 μm as the sense region. _a1 On top of the Ta (tantalum) layer 34 _a2 Through the W (tungsten) layer 34 _a3 34) _a And the other lead conductor layer (FeMn layer 34). _b1 On top of the Ta (tantalum) layer 34 _b2 W layer 34 through _b3 34) _b And are formed.
[0016]
Such an MR head 31 includes an MR layer 33. _c Magnetization direction Mn, the resistance value of which changes according to the signal magnetic field from the magnetic disk 11, and the MR layer 33 _c Is dependent on the relative angle θ with respect to the direction Mi of the sense current Is flowing through.
[0017]
That is, the magnetization vector of the MR element 33 is rotated according to the magnetization direction from the magnetic disk 11, thereby changing the resistivity with respect to the sense current. The resistivity changes substantially according to the cosine square of the angle between the magnetization vector and the current vector, and is expressed by the following equation.
[0018]
ρ = ρ ₀ + Δρ _MAX cos ² θ (1)
Where ρ is resistivity and Δρ _MAX Is the maximum change in resistivity.
[0019]
With this relationship, if the magnetization and current directions match at the beginning, the initial change in resistance change rate due to the magnetization of the recording medium is low. Therefore, the MR element is tilted 45 ° from the easy axis of magnetization of the MR element, and the MR sensor is used with high sensitivity and high linearity.
[0020]
When this MR sensor passes over the recording magnetization on the medium, an electric signal is generated and the signal on the medium can be read by the sensitivity characteristic of the MR element.
[0021]
Next, FIG. 28 shows a cross-sectional view of an essential part schematically showing another conventional magnetic disk device. A composite thin-film magnetic head 51 shown in FIG. 28 includes an MR element 33 in the MR head 31 shown in FIG. 25, a flux guide 52 made of a NiFe alloy film whose tip is exposed on the surface facing the magnetic disk, and an insulation not shown at the rear end. This is magnetically coupled through a thin film, and the others are the same as in FIG.
[0022]
Then, a recording signal current is passed through the coil 40 of the recording magnetic head 37 in the composite thin film magnetic head 51, thereby the first and second magnetic poles 35. _a , 41 is magnetized from a CoCr film having magnetic anisotropy in the in-plane direction via a Cr underlayer film 13 on a nonmagnetic substrate 12 in the opposite magnetic disk 11 by a magnetic flux leaking from the gap between the tip ends of both ends. Magnetic recording of information is performed on the magnetic recording film 14.
[0023]
By introducing the magnetic flux leaking from the magnetic recording film 14 of the magnetic disk 11 on which information has already been recorded into the MR element 33 through the flux guide 52 of the reproducing MR head 31, magnetization according to the change of the magnetic flux is performed. Reproduction is performed by detecting a reproduction signal obtained by taking a change in electrical resistance of the MR element 33 caused by the magnetoresistive effect at that time as a change in voltage.
[0024]
Note that the magnetic flux leaking from the magnetic recording film 14 is introduced into the MR element 33 via the flux guide 52. This is the case when the tip of the MR element 33 is directly exposed to the disk facing surface. When the thin film magnetic head 51 comes into contact with the opposing magnetic disk 11, a part of the sense current flowing through the MR element 33 leaks to the magnetic disk 11 and short-circuits to damage the tip of the MR element 33 and the disk surface.・ This is to prevent destruction.
[0025]
[Problems to be solved by the invention]
Incidentally, in the magnetic disk apparatus shown in FIG. 24, in order to record information on the magnetic disk 11, a signal current is applied to the coil 25 of the thin film magnetic head 21 and recorded on the first and second magnetic poles 23 and 26. The residual magnetization remains, and at the time of reproduction, the leakage magnetic flux from the magnetic recording film 14 of the magnetic disk 11 is read by the first and second magnetic poles 23 and 26 in the state where the residual magnetization remains.
[0026]
At that time, the change in the magnetization of the tips of the first and second magnetic poles 23 and 26 due to the leakage magnetic flux from the magnetic recording film 14 of the magnetic disk 11 is not smoothly performed and becomes irregular (unstable). There is a problem that an error occurs in the reproduction signal, which is largely reflected in the reproduction waveform and causes the reproduction waveform to be distorted.
[0027]
The reason why the change in magnetization of the magnetic pole tip having remanent magnetization is not performed smoothly but becomes irregular is, for example, that the magnetic domain wall in the magnetic pole tip must move smoothly due to the leakage magnetic flux. If there are impurities, defects, etc. in the vicinity of the magnetic domain wall, and there is residual magnetization at the tip of the magnetic pole, the pinning action due to the impurities, defects, etc. (the action of the domain wall moving slowly and moving irregularly in the energy state) This is because the domain wall does not move smoothly and becomes irregular (unstable).
[0028]
Such a problem is particularly caused by a double-layered magnetic disk and a single-pole type perpendicular magnetic layer in which a soft magnetic backing layer made of, for example, a NiFe alloy film and a perpendicular recording film made of a CoCr film having magnetic anisotropy in the vertical direction are laminated. This occurs remarkably at the tip of the single magnetic pole of the single magnetic pole type perpendicular magnetic head in the apparatus combined with the head, reducing the reliability of the reproduced signal quality.
[0029]
Further, for example, the first and second magnetic poles 23 and 26 of the thin film magnetic head 21 immediately after performing magnetic recording in the magnetic disk apparatus shown in FIG. 24 are magnetized, and a part of the domain wall moved in the magnetic poles by the magnetization is recorded. Even after completion, it remains in an unstable position due to the presence of impurities, defects, etc., and momentarily referred to as Uyghur noise or popcorn noise due to sudden movement of its domain wall to a stable position after a transition to subsequent reproduction. There is a problem that a high level of noise is generated.
[0030]
Here, FIG. 29 shows a waveform diagram for explaining the reproduction waveform of FIG. As described above, when the domain wall moves irregularly, Uyghur noise a (FIG. 29A) and popcorn noise b (FIG. 29B) are generated in the reproduced waveform.
[0031]
In order to solve such a problem, a weak current is passed through the coil 25 of the thin film magnetic head 21 immediately after the magnetic recording is finished, so that the domain wall of the magnetized magnetic pole portion is moved to a stable position in advance. The present applicant has already proposed Japanese Patent Application No. 3-0552020 to prevent the occurrence of popcorn noise at the initial stage of reproduction by reproducing the image.
[0032]
However, regarding the movement of the domain wall remaining at the unstable position, especially when the domain wall is pinned due to the presence of impurities, defects, etc., the soft magnetism that constitutes the first and second magnetic poles 23, 26 A current value that gives a magnetic field to the extent that the film is saturated and magnetized is required. However, such a magnetic field gives rise to residual magnetization at the tip of the magnetic field.
[0033]
In addition, the magnetic field generated from the tips of the magnetic poles whose shapes are narrowed down is considerably large, and the magnetic disk is particularly in the case where such a magnetic pole tip is a single magnetic pole tip of a perpendicular magnetic recording type thin film perpendicular magnetic head. There is a problem that the possibility of adverse effects such as demagnetizing or demagnetizing the recording magnetization of the recording medium increases.
[0034]
On the other hand, also in the magnetic disk apparatus of FIGS. 25 and 28, the first magnetic pole 35 which also serves as a magnetic shield is caused by flowing a recording signal current through the coil 40 of the recording magnetic head 37 of the composite thin film magnetic head 30 or 51. _a And the second magnetic pole 41 have residual magnetization, and these magnetic poles (particularly the first magnetic pole (the magnetic shield layer 35)). _a In the same manner, residual magnetization is also generated in the flux guide 52 of the reproducing MR head 33 provided adjacently by the magnetic field from the recording magnetization of ()).
[0035]
Here, FIG. 30 shows an explanatory diagram of the remanent magnetization of the first magnetic pole (magnetic shield layer), and FIG. 31 shows a waveform diagram explaining a change in output characteristics of the MR head.
[0036]
That is, as shown in FIG. _a When the MR head 31 absorbs the leakage magnetic flux from the magnetic recording film 14 of the magnetic disk 11 in the state where the residual magnetization is generated at the tip of the magnetic disk 11 and the residual magnetization is generated in the flux guide 52, the magnetic domain of the MR element 33 is absorbed. The magnetization of the tip of the flux guide 52 due to the residual magnetic flux is not smoothly changed and becomes irregular (unstable).
[0037]
Therefore, as shown in FIG. 31, there is a problem that an output fluctuation of the read waveform of the MR head occurs and an error occurs because the read waveform becomes asymmetrical in the vertical direction and distorts the reproduction waveform.
[0038]
Such a phenomenon has been attempted by optimally setting the sense current value for each of the plurality of MR heads 31 mounted on the magnetic disk device. Although there is an effect in recovering the state, there is a head in which the up / down asymmetry state is not lost only by changing the sense current due to variations in the head, and the effect on the occurrence of the output fluctuation cannot be seen. There is a problem that the reliability of the reproduction system cannot be improved.
[0039]
SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to provide a magnetic disk device that eliminates reproduction waveform distortion due to residual magnetization during reproduction and prevents errors in the reproduction signal.
[0040]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides a magnetic disk having a magnetic film for recording information, a magnetic head element for recording information on the magnetic disk, and a magnetoresistive effect element. In a magnetic disk drive incorporating a reproducing magnetic head element formed by connecting a flux guide to the magnetic thin film head and an integrated composite thin film magnetic head adjacent to the longitudinal direction of the recording track, the reproducing magnetic head element comprises: Information recorded on the magnetic disk after a series of information is recorded on the magnetic disk by the magnetic head element for recording, having a degaussing coil formed by winding the flux guide through a nonmagnetic material Corresponds to the last information before reading A current that generates a magnetic field opposite to the magnetic field acting on the tip of the flux guide by the recording current is generated. A power supply circuit is provided that supplies the demagnetizing coil to set the magnetization state of the tip of the flux guide to a predetermined stable state.
[0041]
According to a second aspect of the present invention, in the first aspect, the magnetic disk is a perpendicular magnetic disk in which a perpendicular recording film having perpendicular magnetic anisotropy is laminated on a soft magnetic backing layer, and the recording magnetic head is a single pole head. .
[0042]
According to a third aspect of the present invention, in the first aspect, one magnetic pole of the recording magnetic head element also serves as a shield portion of the reproducing magnetic head element.
[0045]
According to a fourth aspect of the present invention, when the current is supplied by the demagnetization power supply circuit according to any one of the first to third aspects, the composite thin film magnetic head is mounted on the magnetic disk. Non-recording area Move to.
[0046]
[Action]
According to the first and second aspects of the invention, a horizontal thin film magnetic head element for recording information on a horizontal recording magnetic disk having in-plane magnetic anisotropy, or a perpendicular recording magnetic disk having perpendicular magnetic anisotropy. Composite consisting of a perpendicular thin film magnetic head element for recording information and a reproducing magnetic head element composed of a magnetoresistive effect element magnetically coupled with a flux guide at the tip, adjacent to each other in the longitudinal direction of the recording track. Before reading information recorded on the magnetic disk in the degaussing coil, a degaussing coil is provided around the flux guide of the reproducing magnetic head element in the thin film magnetic head. A current that generates a magnetic field opposite to the magnetic field acting on the tip of the flux guide by the recording current corresponding to the last information is generated. By flowing, the magnetization state of the tip portion of the flux guide is set to a predetermined stable state.
[0047]
Therefore, in reproducing information from a horizontal recording magnetic disk or a vertical recording magnetic disk, the reproduction guide of the reproduced waveform is obtained by setting the flux guide of the reproducing magnetic head element in the composite thin film magnetic head as described above to a constant magnetization state. Output fluctuations and vertical asymmetry can be reduced, and errors in the reproduction signal can be prevented.
[0048]
According to a third aspect of the present invention, the composite thin film magnetic head has a configuration in which one magnetic pole of the recording magnetic head element also serves as a shield part of the reproducing magnetic head element. Therefore, the flux guide is easily affected by the recording magnetic field of the recording magnetic head element, but the flux guide can be brought into a constant magnetization state by the degaussing coil of the flux guide.
[0051]
Claim 4 In the present invention, when a current is passed through the degaussing coil, the composite thin film magnetic head is moved to a predetermined position, that is, a non-recording area such as a CSS zone or a gap area other than the information recording area. It is possible to completely eliminate the adverse effect on the magnetization recorded on the magnetic disk due to the magnetic field generated by energizing the current for stabilizing the current.
[0052]
【Example】
Embodiments of the present invention will be described below in detail with reference to the drawings.
[0053]
FIG. 1 is a block diagram for explaining a first embodiment of a magnetic disk apparatus according to the present invention.
[0054]
In this embodiment, as shown in the figure, a magnetic disk 61 which is a magnetic recording medium. _A For example, as in the conventional example shown in FIG. 24, a magnetic anisotropy is provided in the in-plane direction via a Cr underlayer (13) on a non-magnetic substrate (12) made of an aluminum plate subjected to NiP surface treatment. The magnetic recording film (14) made of a CoCr film is laminated. 61 _a Is the magnetic disk 61 _A This is a non-recording area (inner guard band).
[0055]
Also, the magnetic disk 61 _A As shown in FIG. 24, the recording / reproducing thin film magnetic head 62 combined with the slider is an Al slider. ₂ O _Three A first magnetic pole (23) made of a NiFe alloy film in a predetermined region on a nonmagnetic substrate (22) made of, etc., and a coil (25) encapsulated with an interlayer insulating film (24) on the first magnetic pole (23) A second magnetic pole (26) made of a NiFe alloy film is disposed in such a manner that its front ends are exposed to the disk-facing surface, and the rear end portions thereof are magnetically connected. ₂ O _Three It consists of a ring magnetic pole induction type thin film magnetic head coated with a protective film (27) such as a film.
[0056]
Further, 63 is a head positioning mechanism, 64 is a head positioning control circuit, and 65 is a recording / reproduction control circuit having a demagnetizing power supply circuit 66 therein.
[0057]
The magnetic disk 61 _A And rotating the magnetic disk 61 _A The thin film magnetic head 62 supported by the head positioning mechanism 63 is levitated above, and the thin film magnetic head 62 is moved to the magnetic disk 61. _A Positioning is performed by the head positioning mechanism 63 driven by a control signal from the head positioning control circuit 64 in a predetermined area on the surface.
[0058]
Here, FIG. 2 shows a circuit block diagram of the recording / reproducing system of FIG. FIG. 2 shows the recording / reproduction control circuit of FIG. 1, and a predetermined number of thin film magnetic heads 62 are connected to the head IC circuit 71 and controlled.
[0059]
In the reproducing system, the read waveform from the thin film magnetic head 62 is sent to the AGC (auto gain control) amplifier 72 via the head IC circuit 71 and sent to the filter 73 from the AGC amplifier 72.
[0060]
The AGC amplifier 72 performs AGC control on the read waveform, and the filter 73 cuts a high frequency component of the output of the AGC amplifier 72. The output from the filter 73 is sent to the equalizer circuit 74. The equalizer circuit 74 equalizes the read waveform (for example, partial response equalization), and sends the equalized waveform to a VFO (Variable Frequency Oscillator) circuit 75 and a maximum likelihood detection circuit 76.
[0061]
The VFO circuit 75 generates a synchronous clock signal from the equalized waveform from the equalizer circuit 74. The maximum likelihood detection circuit 76 decodes the most likely data string from the equalized waveform from the equalizer circuit 74 and outputs it as a reproduction data string.
[0062]
On the other hand, in the recording system, the write data is write-compensated by a write pre-competition (recording compensation circuit) 77 and sent to the direct write control circuit 78 to generate a write pattern. The direct write control circuit 78 is supplied with a degaussing current for supplying a degaussing current for a predetermined time after the write data from the degaussing power supply circuit 66.
[0063]
Then, the magnetic disk 61 is selected from the thin film magnetic head 62 selected by the direct write control circuit 78 via the write flip-flop 79 and the head IC circuit 71. _A (See FIG. 19 for the configuration of the entire apparatus).
[0064]
FIG. 3 is a view for explaining the demagnetizing current application in the first embodiment of the magnetic disk apparatus of the present invention. As shown in FIG. 3, after recording information by supplying a recording signal current from the recording / reproducing control circuit 65 to the thin film magnetic head 62, a current having a polarity opposite to the polarity of the last recording current, that is, The demagnetizing current is supplied to the coil (coil 25 in FIG. 24) of the thin film magnetic head 62 from the demagnetizing power supply circuit 66 provided in the recording / reproducing control circuit 65, whereby the first magnetic pole (23 generated during recording) is generated. ) And the second magnetic pole (26), it is possible to demagnetize the residual magnetization at the tip of the ring-type magnetic pole.
[0065]
FIG. 4 is a view for explaining the magnetic domain structure at the tip of the magnetic pole (second magnetic pole (26)) of the thin film magnetic head in the first embodiment of the magnetic disk apparatus of the present invention. 4A and 4B schematically show a state in which the magnetic domain structure at the tip of the ring-type magnetic pole of the thin film magnetic head 62 changes after energization of a recording signal current and after energization of a degaussing current. FIG.
[0066]
The magnetic domain at the tip of the ring-type magnetic pole immediately after the recording signal current is supplied to the coil (25), the residual magnetization is generated, and as shown in FIG. It becomes a state that does not become. However, when a current for demagnetization is applied to the coil (25) after that, the residual magnetization at the tip of the ring-type magnetic pole tip becomes demagnetized, and the magnetic domain is stabilized in a hexagonal shape as shown in FIG. It becomes a reflux magnetic domain structure.
[0067]
Therefore, subsequently, the magnetic disk 61 continues. _A In the reproduction of information, the distortion of the reproduction waveform due to the residual magnetization at the tip of the ring-type magnetic pole of the thin-film magnetic head 62 as in the prior art is eliminated, so that an error in the reproduction signal due to the distortion of the reproduction waveform is prevented. It becomes possible.
[0068]
The value of the demagnetizing current opposite to the polarity of the last recording current passed through the coil (25) is the soft magnet that forms the ring-type magnetic poles (first and second magnetic poles 23, 26). For example, it is 10 μA for generating a magnetic field having a value approximately half of the coercive force (Hc) value of the film, and the energization time is about 1 μS.
[0069]
The current value for demagnetization is determined by the material of the magnetic pole, the magnetic characteristics, and the shape of the tip of the magnetic pole. On the contrary, residual magnetization occurs at a current value higher than the determined demagnetizing current value, and demagnetization does not occur at a low current value. It will be enough.
[0070]
Incidentally, the magnetic field generated at the tip of the magnetic pole when the current for demagnetization is applied is about several Gauss, and the influence on the magnetic disk 1 having a coercive force value of several thousand Oersted (Oe) or more with this level of magnetic field. Almost negligible.
[0071]
However, in order to eliminate the influence on the magnetic disk 1 in any situation, the magnetic disk 61 _A After recording is performed by supplying a recording signal current to the coil (25) of the thin film magnetic head 62 for recording information on the magnetic disk 61, as shown in FIG. _A For example, a non-recording area 61 such as a CSS (Contact Start Stop) zone or a gap area other than the information recording area provided in the plane of _a The thin-film magnetic head 62 is temporarily moved upward, and a demagnetizing current is applied to the coil (25) of the thin-film magnetic head 62 over the region, whereby the residual magnetization at the tip of the ring-type magnetic pole Magnetic disk 61 by a magnetic field generated by energizing current for demagnetizing the disk _A It is possible to completely eliminate the adverse effect on the magnetization recording.
[0072]
FIG. 5 schematically shows a second embodiment in which the embodiment of the magnetic disk apparatus of the present invention is applied to a magnetic disk apparatus in which a perpendicular magnetic recording type magnetic disk and a single pole type vertical thin film magnetic head are combined. A partial sectional view is shown.
[0073]
Magnetic disk 61 in this embodiment _B As shown in the figure, a perpendicular made of a CoCr film having a magnetic anisotropy in the vertical direction is placed on a nonmagnetic substrate 81 made of an aluminum plate subjected to surface treatment by NiP plating with a soft magnetic backing layer 82 made of a NiFe film. This is a perpendicular magnetic disk having a two-layer structure in which a recording film 83 is laminated.
[0074]
Further, the perpendicular magnetic disk 61 _B On the other hand, the perpendicular thin film magnetic head 91 for recording / reproducing information is sandwiched by an interlayer insulating layer 94 on a nonmagnetic member 93 made of glass or the like embedded in a coil arrangement region of a ferrite substrate 92 serving as a return yoke. The leading end of the main magnetic pole 96 made of NiFe film is exposed on the leading end surface of the head through the coil 95, and the trailing end is arranged in a state of being magnetically coupled to the ferrite substrate 92, and further on the surface thereof. Al ₂ O _Three A protective film 97 such as a film is coated.
[0075]
FIG. 6 is a block diagram for explaining a second embodiment of the magnetic disk apparatus of the present invention. FIG. 6 shows the perpendicular magnetic disk 61. _B And a perpendicular thin film magnetic head 91, and the perpendicular thin film magnetic head 91 has a recording / reproducing control circuit 65 for controlling recording / reproducing signals for the perpendicular magnetic thin film magnetic head 91, as in the first embodiment. A demagnetizing power supply circuit 66 for supplying a demagnetizing current to the 91 coil 95 is provided.
[0076]
The rotated perpendicular magnetic disk 61 is rotated. _B In the state where the perpendicular thin film magnetic head 91 supported by the head positioning mechanism 63 is levitated above, the head positioning mechanism 63 is driven and positioned in a predetermined area by a control signal from the head positioning control circuit 64.
[0077]
Subsequently, after recording information by supplying a recording signal current to the perpendicular thin-film magnetic head 91 from the recording / reproducing control circuit 65 as shown in FIG. 3, the polarity of the last recording current is determined. A current having the opposite polarity, that is, a demagnetizing current is energized to the coil 95 of the perpendicular thin film magnetic head 91 from the demagnetizing power supply circuit 66 provided in the recording / reproducing control circuit 65 under the same conditions as in the first embodiment. As a result, it is possible to demagnetize the remanent magnetization at the tip of the main magnetic pole 96 of the perpendicular thin film magnetic head 91 generated during the recording of information.
[0078]
Accordingly, subsequently, the perpendicular magnetic disk 61 is subsequently continued. _B When the information is reproduced, the distortion of the reproduction waveform due to the residual magnetization at the front end of the main pole of the perpendicular thin film magnetic head 91 as in the conventional example is eliminated as in the first embodiment. It is possible to prevent the occurrence of an error in the reproduced signal.
[0079]
FIG. 7 shows an embodiment of the magnetic disk apparatus of the present invention, a composite thin film magnetic head in which a horizontal magnetic recording type magnetic disk, a ring magnetic pole induction type thin film magnetic head element, and a magnetoresistive thin film head element are integrally formed. FIG. 3 is a cross-sectional view of a main part schematically showing a third embodiment applied to a magnetic disk device in combination with
[0080]
Magnetic disk 61 of this embodiment _A As in the conventional example shown in FIG. 24, a magnetic recording film 103 made of a CoCr film having magnetic anisotropy in the in-plane direction is laminated on a nonmagnetic substrate 101 with a Cr underlayer film 102 interposed therebetween.
[0081]
Also, the magnetic disk 61 _A On the other hand, as a composite thin film magnetic head 111 for recording / reproducing information, a reproducing magnetic head element (reproducing MR head element) 112 and a recording magnetic head element 113 are integrally disposed as shown in the figure. Al their surface ₂ O _Three The structure is covered with a protective film 114 such as a film.
[0082]
The reproducing MR head element 112 is an Al slider. ₂ O _Three A magnetic shield 116 made of a NiFe alloy film on a nonmagnetic substrate 115 made of, etc., a flux guide 117 with the tip exposed on the disk-facing surface on the magnetic shield 116, and an insulating thin film (not shown) at the rear end. A magnetoresistive effect element (hereinafter abbreviated as an MR element) 118 made of a NiFe alloy film bonded to the substrate and a one-turn demagnetizing coil 119 are wound around the flux guide 117, ₂ O _Three It is arranged in a state of being encapsulated by an insulating film 120 made of, for example.
[0083]
The recording magnetic head element 113 includes a first magnetic pole 121 made of a NiFe alloy film also serving as a magnetic shield on the reproducing MR head element 112, and a coil 123 encapsulated with an interlayer insulating film 122 on the first magnetic pole 121. The second magnetic pole 124 made of a NiFe alloy film is disposed in such a manner that its leading ends are exposed to the disk facing surface and their rear end portions are magnetically connected to each other.
[0084]
FIG. 8 is a block diagram for explaining a third embodiment of the magnetic disk apparatus of the present invention.
[0085]
As shown in FIG. 8, in the recording / reproducing control circuit 65 for controlling the recording / reproducing signal for the composite thin film magnetic head 111, the demagnetization provided in the composite thin film magnetic head 111 as in the first and second embodiments. A demagnetizing power supply circuit 66 to be energized to the coil 119 (see FIG. 7) is provided.
[0086]
Then, the rotating magnetic disk 61 of the horizontal magnetic recording system is used. _A The composite thin-film magnetic head 111 supported by the head positioning mechanism 63 is levitated above, and the head positioning mechanism 63 is driven and positioned in the predetermined recording area by a control signal from the head positioning control circuit 64.
[0087]
Here, FIG. 9 shows a circuit block diagram of the recording / reproducing system of FIG. In FIG. 9, the recording / reproduction control circuit 65 has a configuration in which the demagnetization power supply circuit 66 supplies current to the demagnetization coil 119 via the amplifier 80 at the timing of the end of writing by the direct write control circuit 78. This is the same as FIG.
[0088]
FIG. 10 is a diagram for explaining the demagnetizing current in the third embodiment of the present invention. As shown in FIG. 10, after recording information by supplying a recording signal current from the recording / reproducing control circuit 65 to the recording magnetic head element 113 in the composite thin film magnetic head 111, Current that generates a magnetic field opposite to the magnetic field acting on the tip of the flux guide by the recording current of the last polarity of the recording current For example, in the composite thin film magnetic head 111, a magnetic current of 0.3 mA that generates a magnetic field having a value approximately half the coercive force (Hc) of the soft magnetic film forming the flux guide 117 of the reproducing MR head element 112 is used. A reproducing MR head element generated at the time of recording information by energizing a demagnetizing coil 119 provided in the reproducing MR head element 112 from a demagnetizing power supply circuit 66 provided in the recording / reproducing control circuit 65 with a current of 1 μS. It is possible to easily demagnetize the remanent magnetization at the tip of the 112 flux guide 117.
[0089]
Therefore, subsequently, the magnetic disk 61 continues. _A When the information is reproduced, the reproduction waveform distortion due to the residual magnetization at the tip of the flux guide 117 of the reproducing MR head element 112 is eliminated as in the first and second embodiments. It is possible to prevent the occurrence of an error in the reproduction signal due to the above.
[0090]
Next, FIG. 11 shows a cross-sectional view of the essential part schematically showing a fourth embodiment of the magnetic disk apparatus of the present invention. FIG. 11 shows a magnetic disk apparatus according to an embodiment of the present invention in which a magnetic disk of a perpendicular magnetic recording system is combined with a composite thin film magnetic head in which a single magnetic pole type perpendicular magnetic head element and a magnetoresistive element are integrated. This is applied to a disk device.
[0091]
The perpendicular magnetic disk 61 of this embodiment _B As in the second embodiment shown in FIG. 5, a perpendicular recording film 83 made of a CoCr film having magnetic anisotropy in the vertical direction is laminated on a nonmagnetic substrate 81 via a soft magnetic backing layer 82 made of NiFe film. It consists of a two-layer structure.
[0092]
Also, the perpendicular magnetic disk 61 _B As for the composite thin film magnetic head 131 for recording / reproducing information, the tip portion of the composite thin film magnetic head 131 is opposed to the disk on a nonmagnetic member 93 made of glass or the like embedded in the main magnetic pole arrangement region of the ferrite substrate 92 serving as a return yoke. A magnetoresistive element comprising a flux guide 133 exposed around the surface and wound around one turn of a degaussing coil 132 and a NiFe film magnetically coupled to the rear end of the flux guide 133 via an insulating thin film (not shown). MR element) 134 is Al ₂ O _Three It is arranged in a state of being encapsulated by an interlayer insulating film 135 made of a film or the like.
[0093]
On the flux guide 133 and the MR element 134 encapsulated by the interlayer insulating film 135, the recording coil 136 and the front end are exposed at the front end surface of the head, and the rear end is magnetically coupled to the ferrite substrate 92. Main magnetic poles 137 are laminated with an interlayer insulating film 135 interposed therebetween, and further on the surface thereof Al ₂ O _Three A protective film 138 such as a film is coated.
[0094]
Also in the magnetic disk apparatus having such a configuration, the perpendicular magnetic disk 61 rotates in the same manner as in the third embodiment shown in FIG. _B The composite thin film magnetic head 131 supported by the head positioning mechanism is levitated above, positioned in a predetermined recording area, and information is recorded by a recording signal current from the recording / reproducing control circuit.
[0095]
After the information recording, a current opposite to the polarity of the last recording current, for example, a magnetic field having a value of about ½ of the coercive force (Hc) of the soft magnetic film forming the flux guide 133 is applied. By applying a current to be generated to the demagnetizing coil 132 provided around the flux guide 133 of the composite thin film magnetic head 131 from the demagnetizing power supply circuit 66 provided in the recording / reproducing control circuit 65 for a predetermined time. As in the third embodiment shown in FIG. 7, it is possible to demagnetize the residual magnetization at the tip of the flux guide 133 that has occurred during information recording.
[0096]
Accordingly, subsequently, the perpendicular magnetic disk 61 is subsequently continued. _B When the information is reproduced, since the distortion of the reproduction waveform due to the residual magnetization at the tip of the flux guide 133 of the composite thin film magnetic head 131 is eliminated as in the third embodiment, the reproduction caused by the distortion of the reproduction waveform is eliminated. It is possible to prevent signal errors from occurring.
[0097]
FIG. 12 is a cross-sectional view of a principal part schematically showing a fifth embodiment of the magnetic disk apparatus of the present invention.
[0098]
In this embodiment, as shown in the drawing, a perpendicular magnetic disk 61 having a double-layer structure similar to that of the fourth embodiment shown in FIG. _B On the other hand, as a composite magnetic head 141 for perpendicularly recording / reproducing information, a recording / reproducing coil 143 is formed on the main magnetic pole arrangement region of the ferrite substrate 142 serving as a return yoke. ₂ O _Three The film is embedded in a state of being encapsulated by a first insulating film 144 such as a film.
[0099]
A main magnetic pole 146 that also serves as a flux guide made of a NiFe film is formed on the buried region via a second insulating film 145 made of a diamond-like carbon film. A magnetoresistive effect element (MR element) 147 is arranged in a magnetically coupled state via an Al ₂ O _Three A protective film 148 such as a film is coated.
[0100]
The central portion of the main magnetic pole 146 and a part of the MR element 147 are magnetically connected to the ferrite substrate 142 to constitute a parallel bypass magnetic path.
[0101]
The perpendicular magnetic disk 61 described above is used. _B Also in the magnetic disk device having a configuration in which the thin film magnetic head 141 and the composite thin film magnetic head 141 are combined, the perpendicular magnetic disk 61 that rotates as in the first and second embodiments _B The composite thin film magnetic head 141 is levitated above, positioned in a predetermined recording area, and information is recorded by a recording signal current from the recording / reproducing control circuit 65 (see FIG. 2).
[0102]
After the information recording, the coercive force (Hc) of the soft magnetic film made of NiFe forming the main electrode 146 also serving as the flux guide, for example, the current having the opposite polarity to the last recording current. A current for generating a magnetic field having a value of approximately ½ is supplied to the coil 143 of the composite thin film magnetic head 141 from the demagnetizing power supply circuit 66 provided in the recording / reproducing control circuit 65 for a predetermined time (FIG. 2). As in the fourth embodiment shown in FIG. 11, it is possible to easily demagnetize the remanent magnetization at the front end of the main magnetic pole 146 generated during the recording of information.
[0103]
Therefore, subsequently, the magnetic disk 61 continues. _B When the information is reproduced, since the distortion of the reproduction waveform due to the residual magnetization at the tip of the main magnetic pole 146 of the composite thin film magnetic head 141 is eliminated as in the fourth embodiment, the reproduction caused by the distortion of the reproduction waveform is eliminated. It is possible to prevent signal errors from occurring.
[0104]
In the above embodiment, an example in which a NiFe film is used as a material for forming magnetic poles and flux guides has been described. However, the present invention is not limited to this example, and has an equivalent function other than this NiFe film, such as a CoZrNb film. May be used.
[0105]
In the first to fifth embodiments described above, description of bias for functioning the MR element and stabilization of the magnetic domain of the MR element itself is omitted. For example, a SAL (Soft Adjacent Layer) bias, Any one of shunt bias, barber pole bias, exchange bias by diamagnetic film, etc. may be used as appropriate.
[0106]
As described above, after information is recorded on the corresponding magnetic disk by each thin film magnetic head, the thin film magnetic head is temporarily moved to a position in a non-recording area other than the information recording area on the magnetic disk, and each thin film magnetic head is moved. Information is reproduced after demagnetizing the residual magnetization of the ring-type magnetic pole, single magnetic pole, flux guide, or flux guide that also serves as a single magnetic pole by supplying a current for demagnetization to the coil of the magnetic head or the degaussing coil. This eliminates an unexpected adverse effect on the residual magnetization and information recorded on the magnetic disk when the residual magnetization is demagnetized.
[0107]
Next, FIG. 13 shows a configuration diagram of a sixth embodiment of the magnetic disk apparatus of the present invention. FIG. 13A is a main configuration diagram of the magnetic disk device, and FIG. 13B is a circuit block diagram of the recording / reproducing system.
[0108]
In this case, the magnetic disk 61 for horizontal recording _A As a magnetic head, a composite thin film magnetic head 30 (51) in which a recording magnetic head 37 and a reproducing MR head 31 are combined as described in the conventional example is used.
[0109]
Further, the head positioning mechanism 63, the head positioning control circuit 64, and the recording / reproduction control circuit 65 in FIG. 13A are the same as those shown in FIG. In this case, the recording / reproduction control circuit 65 is provided with a stabilizing power supply circuit 151.
[0110]
In the recording / reproduction control circuit 65 shown in FIG. 13B, the stabilization power supply circuit 151 supplies a stabilization current to the direct write control circuit 78. In addition, since it is a component part of the same function as the thing of the same code | symbol as the above-mentioned, description is abbreviate | omitted.
[0111]
FIG. 14 is a diagram for explaining the reproduction stabilization of the sixth embodiment of the present invention. FIG. 14A is a flowchart, and FIG. 14B is a timing chart. 14A and 14B, the magnetic disk 61 as shown in FIG. _A When a read command for reproduction is issued after recording predetermined information (step (S) 1, FIG. 14B), the composite thin film magnetic head 30 is controlled by the head positioning mechanism 63 and the head positioning mechanism. The circuit 64 causes the magnetic disk 61 to _A Non-recording area 61 of _a (S2).
[0112]
Then, a stabilizing current (described later) is supplied to the recording magnetic head 37 from the stabilizing power supply circuit 151 via the direct control circuit 78 in a predetermined direction for a predetermined time, for example, 50 mA (S3, FIG. 14B). In this case, the predetermined time is the electromagnetic shield (first magnetic pole) 35 of the composite thin film magnetic head 30 (51). _a It is necessary and sufficient time that the magnetization state of the film can be changed.
[0113]
When the stabilization current is supplied, the composite thin film magnetic head 30 (51) is moved to the magnetic disk 61. _A Is moved onto the lead track to be reproduced (S4), and a read start is performed (S5).
[0114]
Here, FIG. 15 shows an explanatory diagram of the magnetization state of the shield portion of the composite thin film magnetic head.
[0115]
15 shows a shield portion (electromagnetic shield 35 in FIG. 25). _a ), And generally has three stable states of A to C in the minimum part. Among these, the B state is the most stable, and A and C are metastable states. That is, the magnetization state can be settled in any state of A to C by the write magnetic field, and the characteristics (output values) are different in each, and the output fluctuation becomes large.
[0116]
In this embodiment, a stabilizing current is supplied to the recording magnetic head 37 so as to be in one of the states A and C, thereby the shield 35 of the composite thin film magnetic head 30 (51). _a Is always magnetized in a certain stable state.
[0117]
That is, the state B in FIG. 15 is the most stable state without residual magnetism, but in this embodiment the shield 35 _a Rather than demagnetizing the residual magnetism, a stabilizing current with a constant current direction is supplied to the recording magnetic head 37 to obtain a constant magnetization state. This can be easily prevented and reading errors can be reduced.
[0118]
FIG. 16 is a graph showing the relationship between the stabilized current and the output fluctuation. FIG. 16 shows the output fluctuation ratio and the vertical asymmetric fluctuation ratio when a current of 40 mA in both directions, 40 mA in one direction, and 50 mA in one direction is supplied to the recording magnetic head 37 before the MR head 31 is read. It is shown.
[0119]
As shown in the figure, it is clear that each fluctuation rate is low when a stabilized current of 40 mA and 50 mA is supplied in one direction. In this case, the normal write current is 40 mA, and each fluctuation rate can be reduced by supplying a similar or higher current value of several μS or less.
[0120]
The supply of the stabilizing current is assumed to be before reading, but “before reading” includes the case immediately before reading by the MR head 31 and the case immediately after writing by the recording magnetic head 37.
[0121]
This embodiment can also be applied to the configuration in the fifth embodiment.
[0122]
Next, FIG. 17 shows a configuration diagram of another embodiment of the sixth embodiment. 17A is a main configuration diagram of the magnetic disk device, and FIG. 17B is a circuit block diagram of the recording / reproducing system.
[0123]
FIGS. 17A and 17B show the case where the composite thin film magnetic heads 111 and 131 used in the third and fourth embodiments are used, and for demagnetization formed around the flux guides 117 and 133. FIG. A stabilizing current is supplied to the coil 119 from the stabilizing power supply circuit 151 via the amplifier 80, and other configurations are the same as those in FIG.
[0124]
That is, the magnetization state of the flux guides 117 and 133 is always kept constant as shown in FIG. 15 to reduce the output fluctuation and the vertical asymmetry of the MR head 112, thereby reducing the reading error.
[0125]
When supplying the stabilizing current from the stabilizing power supply circuit 151, the composite thin film magnetic head 30 (51, 111, 131, 141) is connected to the magnetic disk 61. _A , 61 _B It may be separated from the surface in the vertical direction. That is, the composite thin-film magnetic head 30 (51, 111, 131, 141) is retracted from the recording area or separated from the disk surface, thereby preventing the recording area from being affected by the stabilized current supply.
[0126]
Next, FIG. 18 shows a block configuration diagram of erase control of the seventh embodiment of the present invention. In the embodiment shown in FIG. 18, the magnetic recording medium used may be either a horizontal or vertical magnetic disk, and the magnetic head is a reproducing MR head element comprising a thin film inductive recording magnetic head element and an MR element. A composite thin film magnetic head is used. Further, the reproducing MR head element in the composite thin film magnetic head may be constituted by connecting the MR element to a flux guide. In FIG. 18, the same reference numerals as those in the above embodiment have the same functions, and the description thereof is omitted.
[0127]
FIG. 18 is a main block diagram of a recording system of a magnetic disk apparatus as a recording / reproducing apparatus in the seventh embodiment. A read error signal of a read error that occurs during reproduction is an MPU (microprocessor) 161, and a write gate output means 162. And dummy write data output means 163 which is pseudo record information output means.
[0128]
The MPU 161 includes a magnetic disk 61 _A (61 _B ), A dummy data recording area 61 which is a pseudo recording area in which data is not recorded. _a (For example, the magnetic disk 61 shown in FIG. _A Non-recording area (inner guard band) 61 _a Or a command to move the composite thin film magnetic head (described in FIG. 19) to the outer guard band on the outer peripheral side is sent to the seek control means 164.
[0129]
The seek control means 164 sends an on-track signal to the effect that the thin film magnetic head has been on-tracked to the dummy data recording area to the direct write control circuit 78 and the write gate output means 162.
[0130]
In addition, dummy write data which is pseudo recording information from the write gate and write data output means 163 from the write gate output means 162 is sent to the direct write control circuit 78.
[0131]
Then, after receiving the on-track signal, the direct write control circuit 78 applies a write current based on the dummy write data between the write gate signals via the write flip-flop (write FF) 79 and the amplifier 165 provided in the head IC circuit. The magnetic head 168 is supplied to the inductive recording magnetic head 166.
[0132]
FIG. 19 is an overall block diagram of the magnetic disk device in the seventh embodiment. In the figure, the same reference numerals as those in the above embodiment are assumed to have the same functions, and the description thereof is omitted.
[0133]
In FIG. 19, as a device control system, a magnetic disk device 170 receives commands from an external host device 171 as input to the MPU 161 via an interface (scsi) controller 172 as an interface, and commands from the MPU 161 pass through the digital LSI 173. Sent through. A read / write gate signal is sent from the SCSI controller 172 to the digital LSI 173. The SCSI controller 172 is provided with a DRAM (Dynamic Random Access Memory) buffer 174, and the MPU 161 is provided with a ROM (Read Only Memory) 175 and a RAM 176.
[0134]
Further, a read gate signal is sent from the SCSI controller 172 to the control logic 177 and a write gate signal is sent from the digital LSI 173 to output any one of the signals to the recording / reproducing decoder 178 and the encoder 179. This control logic 177 becomes the write gate output means 162 of FIG.
[0135]
On the other hand, a DSP (digital signal processor) 180 as a drive system transmits and receives signals such as seek control to and from the digital LSI 173, and drives a DC motor 182 that rotates a magnetic disk via a spindle motor driver 181 and VCM. (Voice coil motor) The VCM 184 for seeking the composite thin film magnetic head 168 is driven via the driver 183. This DSP 180 becomes the seek control means 164 of FIG.
[0136]
The recording / reproducing system has the same configuration as that shown in FIGS. 2 and 9, and includes a composite thin film magnetic head 168 composed of a recording magnetic head (inductive write head) 166 and a reproducing magnetic head (MR head) 167. A head IC circuit 71, an AGC amplifier 72, a filter 73, an equalizer circuit 74, a VFO circuit 75, a maximum likelihood detection circuit 76, a write pre-competition 77, a direct control circuit 78, and a write flip-flop 79 that transmit and receive recording / reproduction signals. Consists of.
[0137]
A head selection signal and a write gate signal are input from the digital LSI 173 by the head IC circuit 189. The output of the filter 73 is sent to the DSP 180 after the cylinder servo information of the magnetic disk is demodulated by the cylinder servo demodulation circuit 185.
[0138]
Then, the reproduction data string from the maximum likelihood detection circuit 76 and the synchronous clock from the VFO circuit 75 are decoded by the decoder 178 and sent to the SCSI1 controller 172 as a parallel reproduction signal decoded by the serial / parallel conversion circuit 186. The write data from the SCSI computer 172 is converted into a serial signal sequence by the parallel / serial conversion circuit 187, encoded by the encoder 179, and sent to the write pre-competition 77.
[0139]
On the other hand, when the magnetic disk device 170 is a servo surface servo system having a servo disk, servo information from the servo head 188 for reading servo information is sent to the servo demodulation circuit 190 via the servo IC circuit 189. The servo demodulation circuit 190 sends the demodulated servo data to the DSP 180 and sends dummy write data to the direct write control circuit 78. This servo demodulating circuit 190 serves as dummy write data output means in FIG. The direct circuit control circuit 78 receives a dummy write execution command (write gate signal) from the MPU via the digital LSI 173.
[0140]
When the control method of the apparatus is the data surface servo method, the servo head 188 and the servo IC circuit 189 are unnecessary, and servo information from the data surface in the cylinder is demodulated by the cylinder demodulation circuit 185 and sent to the DSP 180.
[0141]
FIG. 20 shows a flowchart of erasing in the seventh embodiment, and FIG. 21 shows a timing chart of AC erasing in the seventh embodiment. 20 and 21, even if a slight read error occurs during reproduction, it can be corrected by retrying or the like, but if a read error occurs to such an extent that the error cannot be corrected (S11), the composite thin film magnetic head 168 is attached to the magnetic disk. 61 _A (61 _B ) Dummy data recording area 61 _a Seek to the cylinder (S12).
[0142]
When the seek is completed, a write gate is input as a dummy write execution command signal to the direct write control circuit 78 (FIG. 21A), and dummy write data is supplied from the servo demodulation circuit 190 to supply current to the write head 166. Is supplied (FIG. 21C). Thus, the magnetic disk 61 _A (61 _B ) Dummy data recording area 61 _a The dummy write data is recorded (S13, FIG. 21B).
[0143]
The dummy data is composed of predetermined dummy data D1 and AC erase D2, and as shown in FIGS. 21A to 21C, after writing dummy data D1, which is pseudo recording information, a low-frequency solitary wave (described later). ) AC erase D2 current is supplied to the recording magnetic head 166 for a predetermined time. The current supply time for the dummy data D1 and the AC erase D2 is determined by the write gate signal (FIG. 21A).
[0144]
By this AC erase D2, the shield portion (or flux guide) that also serves as the magnetic pole of the recording magnetic head 166 is interposed between the reproducing magnetic head 167 and the recording magnetic head 166 in the composite thin film magnetic head 168 after data writing. It is intended to demagnetize the residual magnetization.
[0145]
Therefore, the dummy data D1 recorded by the reproducing magnetic head 167 is read (S14), and if no read error occurs, the composite thin film magnetic head 168 is moved to the magnetic disk 61. _A (61 _B ) Is sought to the cylinder that performs the reproduction (S16), and a read retry is performed.
[0146]
On the other hand, if the magnetization is not stabilized and a read error occurs, dummy data write is performed (S13), and dummy data read is performed again (S14). Repeat until no read error occurs. When the read error does not occur, seek to the read error cylinder and perform a read retry.
[0147]
However, if the number of read errors exceeds the predetermined number (X), an alarm is displayed as a head failure (S15). As a result, the cause of the read error can be selected.
[0148]
Thus, the occurrence of residual magnetization can be prevented by performing the AC erase after writing the dummy data D1.
[0149]
Here, FIG. 22 shows a timing chart of DC erase of the seventh embodiment. 22A to 22C show a case where a current having a predetermined polarity of the DC erase D3 is supplied to the recording magnetic head 166 for a predetermined time after the dummy data D1 in FIG. 21 is written.
[0150]
In this case, the DC erase D3 shown in FIGS. 22A to 22C is a medium (magnetic disk 61) based on the last data of the dummy data D1. _A (61 _B It is only necessary to supply a magnetic pole current that stabilizes the magnetization of the head with respect to the polarity of the magnetization reversal in the dummy data recording area).
[0151]
Next, FIG. 23 shows an explanatory diagram of the output change amount of the reproducing magnetic head due to the erase of the seventh embodiment.
[0152]
In FIG. 23A, the recording magnetic head 166 was subjected to 40 mA AC erase (1 MFRPS, 10.5 MFRPS, 63 MFRPS) and 40 mA DC erase a predetermined number of times (measurement number) using five composite thin film magnetic heads 168. In this case, the output change amount (average value) [%] of the reproducing magnetic head 167 is shown. In this case, when the output amount of the average reproducing magnetic head is 100%, for example, head No. 1 is 100-10.8 = 89.2 [%] is 100 + 4.3 = 104.3 [%], indicating that an increase in output amount of 15.1 [%] is recognized. In the figure, “-” indicates that erasing is not performed.
[0153]
Further, as shown in FIG. 23B, the probability of an increase in output when the dummy write time (erase time) is 10 μS, 20 μS, and 30 μS is shown as a case where AC erase is performed. The erase time for DC erase is the time (several μS) for the domain wall in the shield part of the composite thin film magnetic head 168 to move.
[0154]
As shown in FIGS. 23A and 23B, when the frequency of AC erase D2 is 1MFRPS and 10.5MFRPS, the probability that the output recovers beyond the output average value is about 50%. Probability is low at 20%. Therefore, a low frequency is suitable as the frequency.
[0155]
In the case of DC erase D3, there is only one data, but the probability is 65%. A recovery rate was obtained.
[0156]
In this way, when the read error occurs, dummy write data is written, and then the current for AC or DC erase is supplied to the recording magnetic head, so that the shield portion of the composite thin film magnetic head has stable residual magnetization. And distortion of the playback waveform can be eliminated. As a result, fluctuations in the output of the reproduced waveform and up / down asymmetry are suppressed, error generation is prevented, error recovery and head replacement can be easily performed, and reliability can be improved.
[0157]
【The invention's effect】
As is apparent from the above description, in the first and second aspects of the invention, a horizontal thin film magnetic head element for recording information on a horizontal recording magnetic disk having in-plane magnetic anisotropy, or perpendicular magnetic anisotropy. A perpendicular thin film magnetic head element for recording information on a perpendicular recording magnetic disk having a magnetic recording element and a reproducing magnetic head element composed of a magnetoresistive effect element having a flux guide magnetically coupled to the tip are arranged in the longitudinal direction of the recording track. A demagnetizing coil is provided around the flux guide of a reproducing magnetic head element in a composite thin film magnetic head constructed integrally adjacent to each other, and the last recording before reading the information recorded on the magnetic disk in the degaussing coil. By flowing a current having a polarity opposite to the polarity of the current, the magnetization state of the flux guide tip is set to a predetermined stable state.
[0158]
Therefore, in reproducing information from a horizontal recording magnetic disk or a vertical recording magnetic disk, the reproduction guide of the reproduced waveform is obtained by setting the flux guide of the reproducing magnetic head element in the composite thin film magnetic head as described above to a constant magnetization state. Output fluctuations and vertical asymmetry can be reduced, and errors in the reproduction signal can be prevented.
[Brief description of the drawings]
FIG. 1 is a configuration diagram for explaining a main part of a first embodiment of a magnetic disk apparatus according to the present invention;
FIG. 2 is a circuit block diagram of recording / reproduction of FIG.
FIG. 3 is a diagram for explaining energization of a degaussing electrode in the first embodiment of the magnetic disk apparatus of the present invention;
FIG. 4 is a diagram for explaining the magnetic domain structure of the magnetic pole tip of the thin film magnetic head in the first embodiment of the magnetic disk apparatus of the invention.
FIG. 5 is a sectional view of an essential part schematically showing a second embodiment of the magnetic disk apparatus of the present invention.
FIG. 6 is a configuration diagram for explaining a second embodiment of the magnetic disk apparatus of the present invention;
FIG. 7 is a sectional view of an essential part schematically showing a third embodiment of the magnetic disk apparatus of the invention.
FIG. 8 is a configuration diagram for explaining a third embodiment of the magnetic disk apparatus of the present invention;
FIG. 9 is a circuit block diagram of the recording / reproducing of FIG. 8;
FIG. 10 is a diagram for explaining energization of a degaussing current in the third embodiment of the magnetic disk apparatus of the present invention.
FIG. 11 is a cross-sectional view of an essential part schematically showing a fourth embodiment of the magnetic disk apparatus of the present invention.
FIG. 12 is a cross-sectional view schematically showing a main part of a fifth embodiment of the magnetic disk apparatus according to the present invention.
FIG. 13 is a block diagram of a sixth embodiment of the magnetic disk apparatus of the present invention.
FIG. 14 is an explanatory diagram of reproduction stabilization according to the sixth embodiment of the present invention.
FIG. 15 is an explanatory diagram of the magnetization state of the shield portion of the composite thin film magnetic head.
FIG. 16 is a graph showing the relationship between write current and output fluctuation.
FIG. 17 is a configuration diagram of another embodiment of the sixth embodiment.
FIG. 18 is a block diagram of erase control according to a seventh embodiment of the present invention.
FIG. 19 is an overall block diagram of a magnetic disk device in a seventh embodiment.
FIG. 20 is a flowchart of erase in the seventh embodiment.
FIG. 21 is a timing chart of AC erase according to the seventh embodiment.
FIG. 22 is a timing chart of DC erase according to the seventh embodiment.
FIG. 23 is an explanatory diagram of an output change amount of a reproducing magnetic head by erasing in the seventh embodiment.
FIG. 24 is a cross-sectional view schematically showing a main part of a conventional magnetic disk device.
FIG. 25 is an explanatory diagram when a conventional thin film magnetic head is used.
26 is a bottom view of FIG. 25. FIG.
FIG. 27 is a cross-sectional view of a conventional MR head element and a lead conductor layer.
FIG. 28 is a main part sectional view schematically showing a conventional magnetic disk device.
29 is a waveform chart for explaining the reproduction waveform of FIG. 24. FIG.
30 is an explanatory diagram of residual magnetization of a first magnetic pole (magnetic shield layer). FIG.
FIG. 31 is a waveform diagram illustrating changes in output characteristics of an MR head.
[Explanation of symbols]
61 _A , 61 _B Magnetic disk
61 _a Non-recording area (dummy data recording area)
62 Thin-film magnetic head
63 Head positioning mechanism
64 Head positioning control circuit
65 Recording / playback control circuit
66 Power supply circuit
71 Head IC circuit
72 AGC amplifier
73 Filter
74 Equalizer
75 VFO circuit
76 Maximum likelihood detection circuit
77 Light pre-competition
78 Direct write control circuit
79 Light flip-flop
80 amplifiers
81 Non-magnetic substrate
82 Soft magnetic backing layer
83 Perpendicular recording film
91 Perpendicular thin film magnetic head
92 Ferrite substrate
93 Non-magnetic material
94 Interlayer insulation layer
95 coils
96 Main pole
97 Protective layer
101 Non-magnetic substrate
102 Cr underlayer
103 Magnetic recording film
116 Magnetic shield
117, 133 flux guide
118,134,147 MR element
119,132 Degaussing coil
121 1st magnetic pole
123, 136, 143 coil
124 Second magnetic pole
137,146 Main pole
151 Stabilizing power supply circuit
161 MPU
162 Write gate output means
163 Dummy write data output means
164 Seek control means
165 amplifier
166 Magnetic head for power supply
167 Magnetic head for playback
170 Magnetic disk drive

Claims (4)

A magnetic disk having a magnetic film for recording information;
A composite in which a recording magnetic head element for recording information on the magnetic disk and a reproducing magnetic head element in which a flux guide is connected to a magnetoresistive effect element are adjacent to each other in the longitudinal direction of the recording track. A thin film magnetic head;
In the magnetic disk device incorporating
The reproducing magnetic head element has a degaussing coil formed by winding the flux guide through a nonmagnetic material,
After a series of information is recorded on the magnetic disk by the recording magnetic head element, before the information recorded on the magnetic disk is read , a magnetic field acting on the tip of the flux guide by a recording current corresponding to the last information And a power feeding circuit for supplying a current for generating a magnetic field in the opposite direction to the degaussing coil to set the magnetization state of the tip of the flux guide to a predetermined stable state.   2. The magnetic disk according to claim 1, wherein the magnetic disk is a perpendicular magnetic disk in which a perpendicular recording film having perpendicular magnetic anisotropy is laminated on a soft magnetic backing layer, and the recording magnetic head is a single pole head. Magnetic disk unit.   2. The magnetic disk apparatus according to claim 1, wherein one magnetic pole of the recording magnetic head element also serves as a shield portion of the reproducing magnetic head element.   4. The magnetic disk according to claim 1, wherein when the current is supplied by the demagnetization power supply circuit, the composite thin film magnetic head is moved to a non-recording area of the magnetic disk. apparatus.

Images