JP2006323932A - Thin-film magnetic head having heat-generating element, head gimbal assembly having thin-film magnetic head, magnetic disk device having head gimbal assembly, and magnetic recording and reproducing method using thin-film magnetic head - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thin-film magnetic head having a heat-generating element which has a high projection efficiency in the projection of a magnetic head element owing to heat generation and is capable of reliably evading a WATE in response to the writing magnetic flux of a high frequency. <P>SOLUTION: The thin-film magnetic head includes: the writing magnetic head element having a first magnetic pole layer and a second magnetic pole layer; and a reading magnetic head element having a shield layer which is adjacent to the first magnetic pole layer and mutually opposed each other. At least one heat-generating element for generating heat by energization is arranged between the first magnetic pole layer and the shield layer. At least one heat generation body in the thin-film magnetic head has low inductance capable of generating by energization the magnetic flux of the high frequency which is the same as the frequency of a writing electric current to be applied to the writing magnetic head element and which is vertically directed relative to the lamination surface of the first magnetic pole layer and the shield layer. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a thin film magnetic head including a heating element, a head gimbal assembly (HGA) including the thin film magnetic head, and a magnetic disk device (HDD) including the HGA. Furthermore, the present invention relates to a magnetic recording / reproducing method using such a thin film magnetic head.

  In recent years, in order to further improve the surface recording density in the HDD, a perpendicular magnetic recording system different from the conventional in-plane magnetic recording system has been actively developed.

  In the perpendicular magnetic recording system, the demagnetizing field in the magnetization transition region in the magnetic disk surface is much smaller than in the in-plane magnetic recording system, so that the magnetization transition width can be narrowed. Furthermore, since the recording bit is not easily affected by the thermal fluctuation of magnetization, which is a problem in increasing the recording density in the in-plane magnetic recording method, a stable high recording density can be obtained.

  In a thin film magnetic head (perpendicular magnetic head) used for this perpendicular magnetic recording system, a single magnetic pole structure including a main magnetic pole, an auxiliary magnetic pole as a return yoke, and an exciting coil acting on both magnetic poles is mainly employed. In this case, writing is performed on the magnetic disk by a magnetic field generated from the main magnetic pole. The magnetic flux at this time draws a loop that reaches the auxiliary magnetic pole from the main magnetic pole through the recording layer and the soft magnetic underlayer of the magnetic disk.

FIG. 10 shows the magnetic flux distribution in this single magnetic pole structure. According to the figure, during a write operation, induced by a write coil 1004, magnetic flux generated from the main magnetic pole 1002, via a soft magnetic backing layer 1006 in the magnetic disk, returns to the auxiliary magnetic pole 1003 as flux F _Y Come on. This magnetic flux F _Y further reaches the upper and lower shields 1001 and 1000 of the MR effect element for reading, and affects these shields as a magnetic flux F _S. As a result, a considerable magnetic field is generated from the ends 1001a and 1000a on the head end face side of the upper and lower shields 1001 and 1000, and an abnormal signal is written to a track located several μm to several tens μm away from the track to be written. In some cases, the recording signal may be erased. In this specification, such an abnormal phenomenon is called wide area track erasure (WATE). As described above, in the perpendicular magnetic head, the magnetic flux distribution in the magnetic head element has a great influence on the quality of writing due to the presence of the soft magnetic backing layer unique to the magnetic disk for perpendicular magnetic recording.

As a method of avoiding the WATE described above, for example, as disclosed in Patent Document 1, a backing coil 1005 is provided, it is effective to induce a magnetic flux F _B. Indeed, it is possible to cancel or reduce the magnetic flux F _S by the magnetic flux F _B.

  On the other hand, the track width of thin-film magnetic heads tends to decrease as the recording density increases with the recent reduction in capacity and capacity of HDDs. In order to avoid a decrease in writing and reading ability due to the decrease in the track width, for example, in Patent Documents 2 to 5, although a longitudinal magnetic recording method is used, a heating element is provided in the vicinity of the magnetic head element or in the magnetic head element. Technology is disclosed. In these technologies, the end of the magnetic head element protrudes in the direction of the magnetic disk by thermal expansion due to heat from the heating element, and the magnetic effective distance (magnetic spacing) between the magnetic head element and the magnetic disk surface is increased. It is set to an extremely small value and controlled. Thereby, it is possible to avoid a decrease in writing and reading ability.

Japanese Patent Application Laid-Open No. 2004-164783 US Pat. No. 5,991,113 JP 2003-272335 A JP 2003-168274 A Japanese Patent Laid-Open No. 05-020635

  However, when the heating element as described above is employed in the perpendicular magnetic head, it is very difficult to reliably avoid WAIT.

  Actually, when a perpendicular magnetic head element is projected using a heating element, it is required to have low power consumption and good response. For this reason, it is necessary to increase the efficiency of protrusion due to heat generation, and it is desirable to provide the heating element in the magnetic head element as in the technique disclosed in Patent Document 5. However, in this case, a magnetic flux is induced in the magnetic layer such as a shield or a magnetic pole in the perpendicular magnetic head element by energizing the heating element, and the above-described WAIT may be generated. That is, as described above, the write characteristic of the perpendicular magnetic head element is very sensitive to the magnetic flux distribution in the element. Therefore, if a means for generating a magnetic flux is installed in the element, this write characteristic can be adversely affected.

  At this time, a method of coping with further increasing the magnetomotive force of the backing coil is conceivable, but the gradient of the write magnetic field by the main pole is greatly reduced. In addition, when the number of turns is increased and the magnetomotive force is increased, the resistance of the backing coil is further increased, so that a larger amount of heat is generated together with the resistance of the write coil during the write operation. Here, since the backing coil is generally connected in series with the write coil, the protrusion of the perpendicular magnetic head element due to the amount of heat generated in this way cannot be freely controlled independently of the write operation. Therefore, the method of increasing the magnetomotive force of the backing coil is not suitable for avoiding the above-described WAIT. Furthermore, the magnetic flux induced by the writing coil is high frequency, and it becomes much more difficult to cope with the situation where the magnetic flux generated by the heating element is added to the high frequency magnetic flux.

  Accordingly, an object of the present invention is to provide a thin film magnetic head including a heating element, which has a high protrusion efficiency in the protrusion of the magnetic head element due to heat generation, and can reliably avoid WAIT in response to a high-frequency write magnetic flux. An object of the present invention is to provide an HGA including a thin film magnetic head and an HDD including the HGA.

  It is still another object of the present invention to provide a magnetic recording / reproducing method capable of reliably avoiding WAIT in response to a high-frequency write magnetic flux while controlling the magnetic spacing to a sufficiently small value.

  Before describing the present invention, terms used in the specification will be defined. In the laminated structure of the magnetic head elements formed on the element formation surface of the substrate, it is assumed that the component on the element formation surface side of the reference layer is “down” or “downward” and viewed from the reference layer. It is assumed that the component on the side opposite to the element formation surface is “upper” or “upper”. For example, “there is a shield layer on the insulating layer” means that there is a shield layer on the side opposite to the element formation surface of the insulating layer.

  Further, when comparing the positions of two components in one laminated structure, the closer to the element formation surface is defined as “lower”, and the farther is defined as “upper”. For example, of the two magnetic pole layers provided in the electromagnetic coil element, the “lower magnetic pole layer” means the one closer to the element formation surface. Further, “being directly above” means that within the “upper” region, the region is in a region formed of a position where a perpendicular can be drawn with respect to the reference layer or the surface of the layer.

  According to the present invention, a write magnetic head element including a first magnetic pole layer and a second magnetic pole layer, and a read magnetic head element including a shield layer adjacent to the first magnetic pole layer and facing each other, The at least one heating element that generates heat when energized is provided between the first magnetic pole layer and the shield layer, and the at least one heating element There is provided a thin film magnetic head capable of generating a high-frequency magnetic flux having the same frequency as the write current applied to the magnetic head element and having a direction perpendicular to the laminated surface of the first magnetic pole layer and the shield layer by energization.

  During the write operation, the magnetic flux induced in the first magnetic pole layer of the write magnetic head element reaches the shield layer of the read magnetic head element when returning through the second magnetic pole layer. Also affects the layer. This magnetic flux generates an unnecessary magnetic field at the end of the shield layer, causing WATE. The direction of the magnetic flux is high frequency following the write current.

  Here, the heating element of the present invention generates a high-frequency magnetic flux having the same frequency as the write current applied to the write magnetic head element and having a direction perpendicular to the laminated surface of the first magnetic pole layer and the shield layer by energization. Is possible. Therefore, for example, a high-frequency magnetic flux having a phase opposite to that of the high-frequency magnetic flux that causes WAIT can be generated. Here, the reverse phase is the phase of the current that is flipping simultaneously with the write current, and refers to a phase in which a magnetic flux having a direction to cancel the magnetic flux due to the write current is induced at any time. Refers to the phase of the generated magnetic flux. As a result, the magnetic flux causing WATE can be suppressed by the magnetic flux from the heating element. In other words, it is possible to positively suppress WAIT by applying a high-frequency current for heat generation to the heat generating element.

  Further, the heating element is provided at a position substantially adjacent to the write magnetic head element and the read magnetic head element. Therefore, the protrusion efficiency of the write magnetic head element and the read magnetic head element due to heat generation can be sufficiently increased while avoiding adverse magnetic effects such as causing WAIT as described above.

  Here, it is preferable that the at least one heating element includes at least one coil portion having a coil surface parallel to the laminated surface of the first magnetic pole layer and the shield layer. Furthermore, it is preferable that a plurality of the coil portions are provided and connected in series with each other. With such a configuration of the coil portion, the resistance value can be sufficiently increased due to heat generation, while allowing high impedance matching with a preamplifier, wiring, etc. without greatly deteriorating high frequency characteristics. The inductance can be suppressed within a predetermined range. Furthermore, this eliminates the need to increase the total value of resistance with the write coil by increasing the magnetomotive force of the backing coil, for example.

  Further, it is preferable that the first magnetic pole layer is a main magnetic pole layer, the second magnetic pole layer is an auxiliary magnetic pole layer, and the write magnetic head element is for perpendicular magnetic recording. Since the writing characteristics of a perpendicular magnetic head are very sensitive to the magnetic flux distribution in the head element, generally, if a heating element, which is a means capable of generating magnetic flux in the head element, is installed, adverse effects such as WAIT occur during writing. Can do. Therefore, when the heating element according to the present invention with countermeasures against WATE is employed in the perpendicular magnetic head, the effect is particularly remarkable.

  According to the present invention, there is also provided at least one thin-film magnetic head as described above, a lead wire for supplying current to at least one heating element, and signals for the write magnetic head element and the read magnetic head element. An HGA further comprising a wire and a support mechanism for supporting the thin film magnetic head is provided.

  According to the present invention, furthermore, at least one HGA as described above is provided, at least one magnetic disk, a heat generation control circuit for controlling a current supplied to at least one heat generator, and write and read operations. An HDD further provided with a recording / reproducing circuit for controlling the above is provided.

  Here, it is preferable that the HDD controls the heat generation control circuit and the recording / reproducing circuit, and includes a CPU for driving the heat generation control circuit in synchronization with the writing and / or reading operation. By using such a CPU, more various energization modes for the heating elements can be implemented.

  Further, according to the present invention, the magnetic pole layer provided in the write magnetic head element and the read magnetic head element are provided during writing by applying a write current to the write magnetic head element. The heating element installed between the shield layer adjacent to the pole layer and facing each other is flipped simultaneously with the write current, and the direction of the magnetic flux generated from this heating element is changed within the shield layer. There is provided a magnetic recording / reproducing method for applying a heat generation current in a direction opposite to the direction of the magnetic flux as needed. Here, it is preferable that the heat generation current has an opposite phase to the write current, and the amplitude of the magnetic field generated by the heat generation current is smaller than the amplitude of the magnetic field generated by the write current. Further, it is preferable to apply a direct current to the heating element before the read operation is started by the read magnetic head element or during the read operation from immediately before. Furthermore, it is also preferable to apply a direct current to the heating element before the writing operation is started by the writing magnetic head element and immediately before the writing operation.

  The heating element is flipped at the same time as the writing current, and the direction of the magnetic flux generated from the heating element is such that the direction of the magnetic flux generated from the heating element is opposite to the direction of the magnetic flux due to the writing current in the shield layer as needed, for example, the writing current Apply current that is in reverse phase. Such current acts in the direction in which the magnetic fluxes cancel each other, thereby preventing the generation of a magnetic field that causes WAIT at the end of the shield layer. In addition, since the amplitude of the magnetic field generated by such a current is set to a value smaller than the amplitude of the magnetic field generated by the write current, an adverse effect on the write magnetic field due to the write current can be avoided.

  By controlling the current applied to the heating element as described above, the write magnetic head element protrudes while suppressing the flow of unnecessary magnetic flux in the magnetic head element at the time of writing and reliably avoiding WAIT. A predetermined very small magnetic spacing can be realized and a good write operation can be performed. Further, when a direct current is applied to the heating element before or just before the reading operation starts, the MR effect element sufficiently protrudes due to the heat from the heating element. As a result, a predetermined very small magnetic spacing can be realized and a good read operation can be performed. Furthermore, the heating element can be warmed in advance by applying a direct current to the heating element before starting the writing operation. As a result, it is possible to stably and sufficiently apply the heat generation current during the writing operation from the beginning of writing.

  According to the present invention, the protrusion efficiency of the protrusion of the magnetic head element due to heat generation can be increased, and WAIT can be reliably avoided in response to the high-frequency write magnetic flux.

  EMBODIMENT OF THE INVENTION Below, the form for implementing this invention is demonstrated in detail, referring an accompanying drawing. In the drawings, the same elements are denoted by the same reference numerals. In addition, the dimensional ratios in the components in the drawings and between the components are arbitrary for easy viewing of the drawings.

  FIG. 1 is a perspective view schematically showing a configuration of a main part in an embodiment of an HDD according to the present invention, and FIG. 2 is a perspective view showing an embodiment of an HGA according to the present invention. 3A is a perspective view showing a thin film magnetic head (slider) attached to the tip of the HGA in the embodiment of FIG. 2, and FIG. 3B is a perspective view of FIG. 1 is a plan view schematically showing an embodiment of a magnetic head element.

  In FIG. 1, 10 is a plurality of magnetic disks rotating around the rotation axis of the spindle motor 11, 12 is an assembly carriage device for positioning a thin film magnetic head (slider) 21 on a track, and 13 is this thin film. A recording / reproducing and a heat generation control circuit are shown for controlling the writing and reading operations of the magnetic head and for controlling the current applied to the heating element described later.

  The assembly carriage device 12 is provided with a plurality of drive arms 14. These drive arms 14 can be angularly swung about a pivot bearing shaft 16 by a voice coil motor (VCM) 15 and are stacked in a direction along the shaft 16. An HGA 17 is attached to the tip of each drive arm 14. Each HGA 17 is provided with a thin film magnetic head (slider) 21 so as to face the surface of each magnetic disk 10. A single magnetic disk 10, drive arm 14, HGA 17, and slider 21 may be provided.

  As shown in FIG. 2, the HGA 17 is configured by fixing a slider 21 having a magnetic head element to the tip of a suspension 20 and electrically connecting one end of a wiring member 25 to a terminal electrode of the slider 21. The

  The suspension 20 includes a load beam 22, a flexure 23 having elasticity fixedly supported on the load beam 22, a base plate 24 provided at the base of the load beam 22, and a lead conductor provided on the flexure 23. And a wiring member 25 composed of connection pads electrically connected to both ends thereof. Although not shown, a head driving IC chip may be mounted in the middle of the suspension 20.

  As shown in FIG. 3A, the thin film magnetic head (slider) 21 includes an air bearing surface (ABS) 30 processed so as to obtain an appropriate flying height, and a magnetic head element formed on the element forming surface 31. 32 and four signal terminal electrodes 36 and two drive terminal electrodes 37 exposed from the layer surface of the covering layer 45 formed on the element forming surface 31. Here, the magnetic head element 32 includes an MR effect element 33 for reading, an electromagnetic coil element 34 for writing, and a heating element 35 for projecting the magnetic head element 32 in the magnetic disk direction by thermal expansion. Here, the four signal terminal electrodes 36 are connected to the MR effect element 33 and the electromagnetic coil element 34, and the two drive terminal electrodes 37 are connected to the heating element 35.

  The two drive terminal electrodes 37 are arranged on both sides of the group of four signal terminal electrodes 36, respectively. This is an arrangement capable of preventing crosstalk between the wiring of the MR effect element 33 and the wiring of the electromagnetic coil element 34 as described in JP-A-2004-234792. However, when crosstalk is allowed, the two drive terminal electrodes 37 may be disposed at a position between any of the four signal terminal electrodes 36, for example. In addition, the number of these terminal electrodes is not limited to the form of FIG. In FIG. 3, the number of terminal electrodes is six. However, for example, the number of electrodes may be five and the ground may be grounded to the slider substrate.

  In the MR effect element 33 and the electromagnetic coil element 34, as shown in FIG. 3B, one end of the element reaches the head end surface 300 on the ABS side. When these ends face the magnetic disk, reading by sensing the signal magnetic field and writing by applying the signal magnetic field are performed. The heating element 35 is installed in the magnetic head element 32 and includes a coil portion 350. An end 350 a of the coil portion 350 reaches the vicinity of the head end surface 300.

  The coil surface of the coil unit 350 is parallel to the laminated surface of the magnetic head element 32. That is, the coil surface is perpendicular to the head end surface 300 and parallel to the element forming surface 31. The coil portion 350 is installed at the center of the magnetic head element 32 in the track width direction so that the magnetic head element 32 protrudes symmetrically about its center line (corresponding to the AA line in the figure). Has been.

  With the configuration described above, the heating element 35 has a high projecting efficiency when projecting the magnetic head element by heat generation, as described later, and can generate a low magnetic flux that suppresses a high-frequency magnetic flux that causes WAIT. It has an inductance structure.

  4 is a cross-sectional view taken along line AA of FIG. 3B, showing the configuration of one embodiment of the magnetic head element 32 of FIG. 3B. Note that the number of turns of the write coil layer in FIG. 4 is shown to be smaller than the number of turns in FIG. 3B in order to simplify the drawing. Further, the write coil layer may be one layer, two layers or more, or a helical coil.

  In FIG. 4, reference numeral 210 denotes a slider substrate, which has an ABS 30 facing the surface of the magnetic disk, and floats with a predetermined flying height hydrodynamically on the surface of the rotating magnetic disk during a write or read operation. An MR effect element 33 for reading, a heating element 35, a backing coil portion 43, and an electromagnetic coil element 34 for writing are formed on the element forming surface 31 which is one side surface when the ABS 30 of the slider substrate 210 is the bottom surface. And the coating layer 45 which protects these elements is mainly formed.

  The MR effect element 33 includes an MR multilayer 332, and a lower shield layer 330 and an upper shield layer 334 disposed at positions sandwiching the multilayer. The MR multilayer 332 is composed of an in-plane energization type (CIP (Current In Plain)) giant magnetoresistance (GMR (Giant Magneto Resistive)) multilayer film, a vertical energization type (CPP (Current Perpendicular to Plain)) GMR multilayer film, or a tunnel. It has a magnetoresistive (TMR (Tunnel Magneto Resistive)) multilayer film and senses a signal magnetic field from a magnetic disk with very high sensitivity. The upper and lower shield layers 334 and 330 prevent the MR multilayer 332 from receiving an external magnetic field that causes noise.

  When the MR multilayer 332 includes a CIP-GMR multilayer film, insulating upper and lower shield gap layers 333 and 331 are provided between the upper and lower shield layers 334 and 330 and the MR multilayer 332, respectively. . Further, an MR lead conductor layer 335 for supplying a sense current to the MR multilayer 332 and taking out a reproduction output is formed. On the other hand, when the MR multilayer 332 includes a CPP-GMR multilayer film or a TMR multilayer film, the upper and lower shield layers 334 and 330 also function as upper and lower electrodes, respectively. In this case, the upper and lower shield gap layers 333 and 331 and the MR lead conductor layer 335 are unnecessary and are omitted. However, insulating layers are formed on the shield layer opposite to the head end surface 300 of the MR multilayer 332 and on both sides of the MR multilayer 332 in the track width direction.

  The electromagnetic coil element 34 is for perpendicular magnetic recording in this embodiment, and includes a main magnetic pole layer 340, an auxiliary magnetic pole layer 345, and a writing coil layer 343. The main magnetic pole layer 340 is a magnetic path for guiding the magnetic flux induced by the writing coil layer 343 while converging it to the perpendicular magnetic recording layer of the magnetic disk on which writing is performed, and the main magnetic pole main layer 3400 and the main magnetic pole auxiliary layer. 3401. Here, the length (thickness) in the layer thickness direction of the end portion 340a on the head end surface 300 side of the main magnetic pole layer 340 corresponds to the thickness of the main magnetic pole main layer 3400 alone and is small. As a result, a fine write magnetic field corresponding to higher recording density can be generated.

  The end portion of the auxiliary magnetic pole layer 345 on the head end surface 300 side is a trailing shield portion 3450 having a wider layer cross section than the other portion of the auxiliary magnetic pole layer 345. By providing the trailing shield part 3450, the magnetic field gradient becomes steeper between the end part 3450a of the trailing shield part 3450 and the end part 340a of the main magnetic pole layer 340. As a result, the jitter of the signal output is reduced, and the error rate at the time of reading can be reduced.

  The backing coil portion 43 is formed of a backing coil layer 430 and a backing coil insulating layer 431, and generates a magnetic flux that cancels the magnetic flux loop generated from the electromagnetic coil element 34 and passes through the MR effect element 33, thereby suppressing WAIT. I am trying. Note that the magnetic flux from the backing coil portion 43 also acts in the direction of weakening the gradient of the write magnetic field. Therefore, in order to limit this action within an allowable range, the number of turns of the backing coil layer 430 is set to be equal to or less than the number of turns of the write coil layer 343.

  The heating element 35 is formed on the MR effect element 33 via the insulating layer 41, and the coil portion 350, the first lead conductor layer 3510 and the second lead conductor layer 3511 for energizing the coil portion 350. The lead conductor portion 351 is made of. The end 350a of the coil part 350 reaches the vicinity of the head end surface 300 as described above. The coil surface of the coil portion 350 is parallel to the laminated surface of the main magnetic pole layer 340 and the upper shield layer 334. That is, the coil surface is perpendicular to the head end surface 300, and the normal line 46 is in the vertical direction in the laminated structure. Therefore, the magnetic flux generated from the coil portion 350 is substantially composed of this vertical component, and has almost no component perpendicular to the head end surface 300. Furthermore, the first and second lead conductor layers 3510 and 3511 are opposite in current direction due to energization, so that the generated magnetic field cancels out at a predetermined distance and becomes very weak.

  When the heating element 35 has such a structure, as will be described later, a magnetic flux that suppresses a high-frequency magnetic flux that causes WAIT can be induced.

  Further, the heating element 35 generates heat due to the current flowing through the coil portion 350. Due to this amount of heat, the layer made of an insulating material surrounding the heating element 35 expands itself to push out the MR effect element 33 and the electromagnetic coil element 34, and the ends of these elements on the head end face 300 side are projected in the magnetic disk direction. . Further, the end of the element protrudes due to thermal expansion of the element itself. Due to such protrusion, the magnetic spacing is controlled to a small value, and the writing and reading ability is improved.

  Here, since the heating element 35 is substantially adjacent to the MR effect element 33 and the electromagnetic coil element 34 and is disposed near the head end surface 300, the protrusion efficiency due to heat generation is very high. As a result, it is possible to achieve power saving without requiring a large energization amount to obtain a predetermined protrusion amount, and it is possible to increase the reliability of the heating element 35 because it is not necessary to excessively increase the current density. Become. Further, as will be described later, it is possible to realize a protrusion with good response corresponding to the write and read operations.

  Next, the configuration of the magnetic head element 32 shown in FIG. 4 will be described in more detail with reference to FIG.

First, a first insulating layer 40 made of Al ₂ O ₃ or the like and having a thickness of about 0.05 to 10 μm is formed on a slider substrate 210 made of AlTiC (Al ₂ O ₃ —TiC) or the like. ing. On the first insulating layer 40, a lower shield layer 330 made of, for example, NiFe, NiFeCo, CoFe, FeN, FeZrN or the like and having a thickness of about 0.3 to 3 μm is formed, and an MR multilayer 332 is further formed. . For example, when the MR multilayer 332 includes a TMR multilayer film, the MR multilayer 332 includes a stacked structure in which a magnetization fixed layer, a tunnel barrier layer, and a magnetization free layer are sequentially stacked.

Further, an upper shield layer 334 made of, for example, NiFe, NiFeCo, CoFe, FeN, or FeZrN and having a thickness of about 0.3 to 4 μm is formed so as to sandwich the MR multilayer 332 with the lower shield layer 330. . Further, on the upper shield layer 334, a second insulating layer 41 made of, for example, Al ₂ O ₃ or the like and having a thickness of about 0.1 to 2.0 μm is formed.

  A coil portion 350, a first lead conductor layer 3510, and a second lead conductor layer 3511 are formed on the second insulating layer 41, and further, for example, heat-cured so as to cover these components. A coil insulating layer 352 having a thickness of approximately 0.1 to 5 μm and formed of a resist layer or the like is formed. The heating element 35 is configured by the above laminated structure.

  Here, the coil part 350 has a thickness of about 0.05 to about 0.50 μm, for example, and is made of a material containing NiCu, for example. Here, the content ratio of Ni in NiCu is, for example, about 15 to about 60 atomic%, and preferably 25 to 45 atomic%. Further, the additive for NiCu contains at least one element of Ta, Al, Mn, Cr, Fe, Mo, Co, Rh, Si, Ir, Pt, Ti, Nb, Zr and Hf. Also good. The content of these additives is preferably 5 atomic% or less.

  Moreover, the coil part 350 has a thickness of about 0.05 to about 0.50 μm, for example, and may be made of a material containing NiCr. In this case, the content ratio of Ni in NiCr is, for example, about 55 to about 90 atomic%, and preferably 70 to 85 atomic%. Further, the additive for NiCr contains at least one element of Ta, Al, Mn, Cu, Fe, Mo, Co, Rh, Si, Ir, Pt, Ti, Nb, Zr and Hf. Also good. The content of these additives is preferably 5 atomic% or less.

  Furthermore, the coil part 350 has a thickness of about 0.05 to about 0.50 μm, for example, and may be made of Ta alone or a material containing Ta. Here, as an additive to Ta, at least one element of Al, Mn, Cu, Fe, Mo, Co, Rh, Si, Ir, Pt, Ti, Nb, Zr, and Hf may be included. . The content of these additives is preferably 5 atomic% or less.

  Further, the first and second lead conductor layers 3510 and 3511 may be formed of, for example, one of Au, Au alloy, Cu, and Cu alloy.

A third insulating layer 42 made of, for example, Al ₂ O ₃ or the like and having a thickness of about 0.1 to 2.0 μm is formed so as to cover the heating element 35. Furthermore, a backing coil layer 430 made of, for example, Cu or the like having a thickness of about 0.5 to 3 μm is formed on the third insulating layer 42. Further, for example, thermosetting is performed so as to cover the backing coil layer 430. A backing coil insulating layer 431 having a thickness of about 0.1 to 5 μm and formed of a resist layer or the like is formed. Further, a fourth insulating layer 44 made of, for example, Al ₂ O ₃ or the like and having a thickness of about 0.1 to 2.0 μm is formed so as to cover the backing coil insulating layer 431.

  Further, on the fourth insulating layer 44, for example, a thickness of 0 made of an alloy made of any two or three of Ni, Fe and Co, or an alloy to which a predetermined element is added as a main component thereof, etc. Main magnetic pole main layer 3400 having a thickness of about 0.01 to 0.5 μm and an alloy composed of any two or three of Ni, Fe and Co, or an alloy to which a predetermined element is added as a main component. A main magnetic pole auxiliary layer 3401 having a thickness of about 0.5 to 3 μm is formed.

A gap layer 341 made of, for example, Al ₂ O ₃ or DLC and having a thickness of about 0.01 to 0.5 μm is formed on the main magnetic pole auxiliary layer 3401. Further, on the gap layer 341, for example, thermosetting is performed. A first write coil insulating layer 3440 having a thickness of about 0.1 to 5 μm made of a resist layer or the like is formed. On the first write coil insulating layer 3440, for example, a write coil layer 343 made of Cu or the like and having a thickness of about 0.5 to 3 μm is formed. Further, for example, a heat coil layer 343 is formed so as to cover the write coil layer 343. A second write coil insulating layer 3441 having a thickness of approximately 0.1 to 5 μm and formed of a cured resist layer or the like is formed.

Further, for example, an alloy composed of any two or three of Ni, Fe and Co, or an alloy to which a predetermined element is added as a main component so as to cover the second write coil insulating layer 3441. An auxiliary magnetic pole layer 345 having a thickness of about 0.5 to 5 μm is formed. Further, a coating layer 45 made of, for example, Al ₂ O ₃ is formed so as to cover the MR effect element 33, the heating element 35, the electromagnetic coil element 34, and the like.

  It is obvious that the magnetic head element according to the present invention is not limited to the embodiment described above. For example, the electromagnetic coil element for writing may be based on the longitudinal magnetic recording method. The longitudinal magnetic recording method is not as important as the perpendicular magnetic recording method. However, unnecessary writing and erasing to adjacent tracks should be avoided, and other than the magnetic flux path between the magnetic pole layers in the magnetic head element. It is preferable to suppress the flow of magnetic flux having this path as much as possible. Further, even if the backing coil portion is not provided in the magnetic head element, it is within the scope of the present invention. Actually, the backing coil section generates a magnetic flux in a direction that weakens the gradient of the write magnetic field. Therefore, it is desirable to omit it when the flow of the magnetic flux is below the generation limit of the WAIT.

  FIG. 5 is a cross-sectional view of the magnetic head element 32 for explaining the operational effects of the heating element 35 in the embodiment of FIG.

According to FIG. 5A, the magnetic flux induced in the main magnetic pole layer 340 by energizing the write coil layer 343 during the write operation is transferred to the auxiliary magnetic pole layer 345 through the soft magnetic backing layer 100 in the magnetic disk. come back as the magnetic flux _{F Y.} The magnetic flux F _Y further passes through the upper and lower shield layers 334 and 330 of the MR effect element 33 as the magnetic flux F _S and reaches the soft magnetic backing layer 100 in the magnetic disk 10 to become the magnetic flux 52. At this time, the flow of the magnetic flux _{F S} causes a WATE by generating unnecessary magnetic fields on the end 330a and 334a. As a countermeasure against this WATE, provided backing coil portion 43, thereby reducing the magnetic flux F _S by generating a magnetic flux F _B.

Here, the heating element 35 according to the present invention is provided at a position between the upper shield layer 334 and the backing coil portion 43 according to FIG. This position is in the loop formed by the magnetic fluxes F _S and F _B. Moreover, as described above, the magnetic flux 50 generated from the coil portion 350 of the heating element 35 is directed substantially in the vertical direction (upward in the figure). As a result, the magnetic flux 50 passes through the main magnetic pole layer 340 and the upper and lower shield layers 334 and 330 to induce the magnetic flux 51 at the position of the soft magnetic backing layer 100, and this magnetic flux 51 causes the magnetic flux 52 (which causes WAIT). And magnetic flux F _S ) can be canceled.

Note that the direction of the magnetic flux F _S, that is, the magnetic flux 52 becomes high frequency following the write current. In order to suppress the high-frequency magnetic flux 52, the magnetic flux 51 must have a high frequency in the opposite phase. Here, the reverse phase is the phase of the current that is flipping simultaneously with the write current, and refers to a phase in which a magnetic flux having a direction to cancel the magnetic flux due to the write current is induced at any time. Refers to the phase of the generated magnetic flux.

  In contrast, the heating element 35 is composed of a plurality of coil portions as described above, and the inductance thereof is sufficiently smaller than that of the backing coil portion. Actually, the inductance can be set to 1 nH or less. Therefore, the frequency characteristics of the heating element 35 are sufficiently compatible with the generation of a high frequency in the opposite phase to the magnetic flux 52. This facilitates impedance matching between the heating element 35 and the preamplifier and wiring. As a result, by applying a high-frequency current for heat generation to the heat generating element 35, it becomes possible to actively suppress WAIT.

Even when the flow of magnetic flux is less than or equal to the generation limit of WATE and the backing coil portion 43 is not provided in the magnetic head element 32, the heating element 35 according to the present invention causes a problem of WATE generation. It becomes possible to install without. That is, according to the heating element 35, it is possible to generate a magnetic flux in the direction of suppressing the flow of the magnetic flux F _S, the state exceed the WATE occurrence limit in complicity with the flow of the magnetic flux F _S can be reliably avoided .

  Furthermore, the heating element 35 exists at a position substantially adjacent to the MR effect element 33 and the electromagnetic coil element 34, and the end 350 a of the heating element 35 reaches the vicinity of the head end surface 300. Therefore, the protrusion efficiency of the magnetic head element 32 due to heat generation can be sufficiently increased while avoiding adverse magnetic effects such as causing WAIT as described above.

  In addition, although the heat generating body 35 of this embodiment is installed in the position P1 in FIG.5 (B), it is not limited to this position. For example, it may be at a position P2 between the backing coil portion 43 and the main magnetic pole layer 340. Even in this position, high protrusion efficiency can be realized while avoiding WATE.

  Further, a plurality of heating elements may be arranged at any of the positions described above or at each position. Here, for example, when two heating elements are installed at any position, the coil portion of each heating element is preferably installed at a symmetrical position with respect to the center line of the magnetic head element. As a result, the center of the heat distribution for the protrusion can be aligned with the center line, so that an effective protrusion of the magnetic head element can be realized.

  FIG. 6 is a plan view schematically showing the configuration of various modifications of the heating element according to the present invention. In any of the modifications, the heating element is formed between the upper shield layer and the main magnetic pole layer (or the backing coil part). The coil element is omitted.

According to FIG. 6A, the heating element 60 includes one coil portion 600 and first and second lead conductor layers 6010 and 6011 for energizing the coil portion 600. This coil portion is a U-shaped coil. The coil surface of the coil unit 600 is parallel to the laminated surface of the upper shield layer 334. Here, the U-shaped opening of the coil unit 600 faces the side opposite to the head end surface 300, and the end 600a of the coil unit 600 is located closest to the head end surface.
Also, the first and second lead conductor layers 6010 and 6011 extend opposite to each other, cross the end side 334a perpendicular to the head end surface of the upper shield layer 334, and outside the region directly above the upper shield layer 334. Has been pulled out.

  According to FIG. 6 (B), the heating element 61 is provided with one U-shaped coil portion, similar to the heating element 60, and the U-shaped opening of the coil portion is opposite to the head end surface 300. It is suitable. However, the first and second lead conductor layers 6110 and 6111 extend in directions opposite to each other and cross different end sides 334a and 334b of the upper shield layer 334 to the outside of the region directly above the upper shield layer 334, respectively. Has been pulled out.

  According to FIG. 6C, the heating element 62 includes a single U-shaped coil portion, similar to the heating element 60, but the U-shaped opening of the coil portion faces the track width direction. . Note that the manner in which the first and second lead conductor layers are drawn out is the same as that of the heating element 60, but may be the same as that of the heating element 61.

  According to FIG. 6 (D), the heating element 60 ′ has a configuration in which a plurality of U-shaped coil portions 600 are provided in the heating element 60 and connected in series. The first and second lead conductor layers are drawn out in the same manner as the heating element 60, but may be the same as the heating element 61.

According to FIG. 6E, the heating element 63 includes an upward portion 67 formed by connecting U-shaped coil portions 630, 631 and 632 in series between a predetermined starting point 64 and a turning point 65. The same U-shaped coil parts 633, 634 and 635 are connected in series along each coil part constituting the ascending part 67 from the turning point 65 to the end point 66 in the vicinity of the starting point 64. And a first lead conductor layer 6900 and 6901. The interval W ₁ between the ascending portion 67 and the descending portion 68 formed along each other is compared with the interval W ₂ between the ascending portions 67 facing each other and the interval W ₃ between the descending portions 68 facing each other. It is set to be narrow.

  According to FIG. 6 (F), the heating element 35 includes two lead-shaped conductor layers from between the two heating elements 60 in which two U-shaped coil portions 600 are provided side by side in the track width direction and connected in series. It is the mode which pulled out. That is, it corresponds to the embodiment of the heating element shown in FIG. The position where the lead conductor layer is pulled out of the upper shield layer 334 is the same as that of the heating element 60, but may be the same as that of the heating element 61. Furthermore, the lead conductor layer may be drawn out from the end side 334c of the upper shield layer 334 opposite to the head end surface 300.

  6A to 6F, the heating element is formed on the upper shield layer 334. For example, a backing coil is provided between the heating element and the upper shield layer 334. A part may be provided. Moreover, each coil part may be semicircular or semi-elliptical instead of U-shaped. Furthermore, each coil part may be connected in parallel or as a combination of parallel and series. In any case, it is within the scope of the present invention if the heating element has a sufficiently small inductance to generate a magnetic flux corresponding to a high-frequency write magnetic flux by the coil portion or a combination thereof.

  FIG. 7 is a cross-sectional view taken along line BB in FIG. 3A for illustrating the structure of the drive terminal electrode 37 in FIG.

  In the cross section shown in the same figure, lead electrodes 3510a and 3511a appear, and these electrodes are electrically connected to the first and second lead conductor layers drawn out of the region directly above the upper shield layer, respectively. Connected. Conductive electrode film members 71 and 74 are formed on the lead electrodes 3510a and 3511a, respectively. On the electrode film members 71 and 74, bumps 72 and 75 extending upward are formed by electroplating using the electrode film members 71 and 74 as electrodes. The electrode film members 71 and 74 and the bumps 72 and 75 are made of a conductive material such as Cu. The thickness of the electrode film members 71 and 74 is about 10 to about 200 nm, and the thickness of the bumps 72 and 75 is about 5 to about 30 μm.

  The upper ends of the bumps 72 and 75 are exposed from the covering layer 45, and pads 73 and 76 for heating elements are provided on these upper ends, respectively. A current is supplied to the heating element through the pads 73 and 76. Similarly, the MR effect element and the electromagnetic coil element are connected to the signal terminal electrode 36 (FIG. 3A), but these connection structures are not shown for the sake of clarity of the drawing. .

  FIG. 8 is a block diagram showing a circuit configuration of the HDD recording / reproducing and heat generation control circuit 13 in the embodiment of FIG.

  In FIG. 1, the recording / reproducing and heat generation control circuit 13 includes a CPU 800, a recording / reproducing channel 801, and a preamplifier unit 802. The recording data output from the recording / reproducing channel 801 is supplied to the preamplifier unit 802. The preamplifier unit 802 receives the recording control signal output from the CPU 800 by the write gate 803, and supplies the recording data to the electromagnetic coil element 34 only when the recording control signal instructs a writing operation. At this time, the preamplifier unit 802 supplies a write current to the coil layer 343 in accordance with the recording data, and recording is performed on the magnetic disk.

  Also, a constant current flows from the preamplifier unit 802 to the MR multilayer 332 only when the reproduction control signal output from the CPU 800 and received by the read gate 804 instructs a read operation. At this time, the reproduction signal received by the preamplifier unit 802 from the MR effect element 33 is amplified and demodulated and output to the recording / reproduction channel 801 as reproduction data.

  The preamplifier unit 802 receives a heat generation control signal output from the CPU 800. When the heat generation control signal is an on operation instruction, a heat generation current is applied to the heat generator 35. The current value at this time is controlled to a value corresponding to the heat generation control signal.

  In FIG. 8, the preamplifier unit 802 includes both a recording / reproducing circuit and a heat generation control circuit. Here, the CPU 800 controls both of these circuits, and can drive the heat generation control circuit in synchronization with the read and / or write operations.

  Furthermore, it is obvious that the circuit configuration of the recording / reproducing and heat generation control circuit 13 is not limited to that shown in FIG. For example, the recording / reproducing circuit and the heat generation control circuit may be provided independently, or the writing and reading operations may be specified by signals other than the recording / reproducing control signal. Further, power supply to the heating element 35 may be performed using an independent power source.

  FIG. 9 is a time chart for explaining an embodiment of the magnetic recording / reproducing method according to the present invention.

  According to FIG. 9A, during writing in which the write gate is in an ON state, a heating current 90 having a phase opposite to the writing current (broken line) is applied to the heating element. Here, the reverse phase is the phase of the current that is flipped simultaneously with the write current, and cancels out the high-frequency magnetic flux from the electromagnetic coil element due to the write current at any time at the position of the upper shield layer (and the lower shield layer). The phase is such that a high-frequency magnetic flux having a direction is induced. This reverse phase current 90 works in the direction in which the magnetic fluxes cancel each other even at the position of the soft magnetic backing layer of the magnetic disk, thereby avoiding the formation of an unnecessary magnetic domain structure in the soft magnetic backing layer and the upper shield. Generation of a magnetic field causing WATE at the end of the air bearing surface side of the layer (and the lower shield layer) is prevented.

  The amplitude of the current 90 having the opposite phase is determined from the amount of electric power required to cause the electromagnetic coil element to protrude by a predetermined amount due to heat generation. Therefore, for example, the current amplitude may be calculated by monitoring the temperature of the electromagnetic coil element, which is a measure of the amount of protrusion, and successively feeding back the monitored value. In consideration of the influence of the write current on the write magnetic field, the amplitude of the magnetic field generated by the antiphase current 90 may be set to a value smaller than the amplitude of the magnetic field generated by the write current. preferable.

  By controlling the current applied to the heating element in this way, the electromagnetic coil element is protruded while suppressing the flow of unnecessary magnetic flux in the magnetic head element at the time of writing and avoiding the WAIT reliably. A very small magnetic spacing can be realized and a good write operation can be performed.

  Next, a DC 91 for sufficiently projecting the MR effect element is applied to the heating element before or just before the read operation by the MR effect element is started when the read gate is turned on. Thereafter, the MR effect element sufficiently protrudes due to heat from the heating element, whereby a predetermined very small magnetic spacing can be realized and a good read operation can be performed. In the present invention, since the heat generation control and the recording / reproduction control are independent as described above, unlike the conventional backing coil, the heating element can be driven during the reproduction as described above. .

  According to FIG. 9B, for example, at the time of start-up or the like, before the light gate is turned on, the direct current 92 for sufficiently projecting the electromagnetic coil element is applied to the heating element. Here, this direct current may be applied intermittently, or an alternating current or a pulse current, etc., so that the total power becomes an amount necessary to obtain a predetermined protruding amount. At this time, for example, the current value or the amplitude of the current may be calculated by monitoring the temperature of the electromagnetic coil element that is a measure of the protrusion amount, and successively feeding back the monitored value. When the electromagnetic coil element sufficiently protrudes by the heat from the heating element by the direct current 92, a predetermined very small magnetic spacing is realized, so that a good writing operation can be performed.

  In order to realize the magnetic recording / reproducing method described above, it is necessary to be able to propagate an appropriate amount of heat to both the electromagnetic coil element and the MR effect element with good response to the writing or reading operation. . Furthermore, it must be possible to avoid WAIT by energization for heat generation. Only when these conditions are satisfied can the above-described magnetic recording / reproducing method be realized. Here, even if any embodiment or modification of the thin film magnetic head of the present invention is used, an appropriate amount of heat is transmitted with good response to both the electromagnetic coil element and the MR effect element while avoiding WAIT. Can do. Thereby, the magnetic recording / reproducing method described above can be realized.

  All the embodiments described above are illustrative of the present invention and are not intended to be limiting, and the present invention can be implemented in other various modifications and changes. Therefore, the scope of the present invention is defined only by the claims and their equivalents.

1 is a perspective view schematically showing a configuration of a main part in an embodiment of an HDD according to the present invention. It is a perspective view showing the whole HGA by this invention. It is the schematic of the thin film magnetic head with which the front-end | tip part of HGA in the embodiment of FIG. 2 was mounted | worn, and a magnetic head element. FIG. 4 is a cross-sectional view taken along line AA in FIG. 3B, showing the configuration of one embodiment of the magnetic head element in FIG. 3B. It is sectional drawing of the magnetic head element explaining the effect of the heat generating body in embodiment of FIG. It is a top view which shows roughly the structure of the various change aspect of the heat generating body by this invention. FIG. 4 is a cross-sectional view taken along line B-B in FIG. 3A for illustrating the structure of the drive terminal electrode in FIG. FIG. 2 is a block diagram showing a circuit configuration of an HDD recording / reproducing and heat generation control circuit in the embodiment of FIG. 1. It is a time chart explaining embodiment of the magnetic recording / reproducing method by this invention. It is a distribution map of the magnetic flux in a magnetic head element for demonstrating the cause of WAIT generation.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Magnetic disk 100 Soft magnetic backing layer 11 Spindle motor 12 Assembly carriage apparatus 13 Recording / reproduction and heat generation control circuit 14 Drive arm 15 Voice coil motor (VCM)
16 Pivot bearing shaft 17 Head gimbal assembly (HGA)
20 Suspension 21 Slider 210 Slider substrate 22 Load beam 23 Flexure 24 Base plate 25 Wiring member 30 Air bearing surface (ABS)
300 Head end surface 31 Element formation surface 32 Magnetic head element 33 MR effect element 330 Lower shield layer 331 Lower shield gap layer 332 MR stack 333 Upper shield gap layer 334 Upper shield layer 334a, 334b, 334c End side 34 Electromagnetic coil element 340 Main Pole layer 340a, 3450a End 3400 Main pole main layer 3401 Main pole auxiliary layer 341 Gap layer 343 Coil layer 344 Write coil insulation layer 3440 First write coil insulation layer 3441 Second write coil insulation layer 345 Auxiliary pole layer 3450 Tray Ring shield part 35, 60, 60 ', 61, 62, 63 Heating element 350, 600 Coil part 350a, 600a End 351, Lead conductor part 3510, 6010, 6110, 6900 First lead conductor Layer 3510a, 3511a Lead electrode 3511, 6011, 6111, 6901 Second lead conductor layer 36 Signal terminal electrode 37 Drive terminal electrode 40 First insulating layer 41 Second insulating layer 42 Third insulating layer 43 Backing coil section 430 Backing coil layer 431 Backing coil insulating layer 44 Fourth insulating layer 45 Cover layer 46 Normal 50, 51, 52 Magnetic flux 64 Start point 65 Turning point 66 End point 67 Up portion 68 Down portion 71, 74 Electrode film member 72, 75 Bump 73 76 Pad 800 CPU
801 Recording / reproduction channel 802 Preamplifier section 803 Write gate 804 Read gate 90 Current 91, 92 DC 1000 Upper shield 1000a, 1001a End 1001 Lower shield 1002 Main magnetic pole 1003 Auxiliary magnetic pole 1004 Write coil 1005 Backing coil 1006 Soft magnetic backing layer

Claims (10)

  Thin-film magnetic head comprising a write magnetic head element including a first magnetic pole layer and a second magnetic pole layer, and a read magnetic head element including a shield layer adjacent to the first magnetic pole layer and facing each other And at least one heating element that generates heat when energized is provided between the first magnetic pole layer and the shield layer, and the at least one heating element includes the write magnetic head element. A thin film magnetic head, wherein a high-frequency magnetic flux having the same frequency as a write current applied to the first magnetic layer and having a direction perpendicular to the laminated surface of the first magnetic pole layer and the shield layer can be generated by energization.   2. The thin film according to claim 1, wherein the at least one heating element includes at least one coil portion having a coil surface parallel to a laminated surface of the first magnetic pole layer and the shield layer. Magnetic head.   The thin film magnetic head according to claim 2, wherein a plurality of the coil portions are provided and are connected in series to each other.   4. The device according to claim 1, wherein the first magnetic pole layer is a main magnetic pole layer, the second magnetic pole layer is an auxiliary magnetic pole layer, and the write magnetic head element is used for perpendicular magnetic recording. 5. The thin film magnetic head according to any one of the above items.   5. A thin film magnetic head according to claim 1, comprising at least one thin film magnetic head, a lead wire for supplying a current to the at least one heating element, the write magnetic head element, and the read magnetic head. A head gimbal assembly, further comprising a signal line for the head element and a support mechanism for supporting the thin film magnetic head.   6. A head gimbal assembly according to claim 5, comprising at least one magnetic disk, a heat generation control circuit for controlling a current supplied to the at least one heat generating element, and control of writing and reading operations. And a recording / reproducing circuit.   7. The CPU according to claim 6, further comprising a CPU for controlling the heat generation control circuit and the recording / reproducing circuit and driving the heat generation control circuit in synchronization with a writing and / or reading operation. The magnetic disk device described.   While writing is performed by applying a write current to the write magnetic head element, the magnetic pole layer provided in the write magnetic head element and the magnetic pole element provided in the read magnetic head element are adjacent to the magnetic pole layer. The heating element installed between the shield layers facing each other is flipped simultaneously with the write current, and the direction of the magnetic flux generated from the heating element is the direction of the magnetic flux due to the write current in the shield layer. A magnetic recording / reproducing method characterized by applying a heating current in a direction opposite to that at any time.   9. The heat generation current has an opposite phase to the write current, and an amplitude of a magnetic field generated by the heat generation current is smaller than an amplitude of a magnetic field generated by the write current. The magnetic recording / reproducing method described.   10. The magnetic recording according to claim 8, wherein a direct current is applied to the heating element before the read operation is started by the read magnetic head element or while the read operation is performed immediately before. Playback method.

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