JP2007133988A - Thin film magnetic head, magnetic head assembly, magnetic disk driver, and compensation method of asymmetrical characteristic - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thin film magnetic head permitting reduction in a bit error rate and an S/N without causing dispersion in MR output, and to provide a magnetic head assembly, a magnetic disk driver, and a compensation method of an asymmetrical characteristic. <P>SOLUTION: The thin film magnetic head is provided with an MR read-out head element, and a magnetic field generation means which is independently arranged outside the MR read-out head element and generates a DC magnetic field to be applied in the direction of the height of the MR read-out head element by making a DC current being independent of a sense current of the MR read-out head element flow. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a thin film magnetic head having a magnetoresistive effect (MR) read head element, a magnetic head assembly having the thin film magnetic head, a magnetic disk drive apparatus having the magnetic head assembly, and compensation of asymmetry characteristics of the MR read head element. Regarding the method.

  When reading magnetic information recorded on a magnetic recording medium such as a magnetic disk, in particular perpendicular magnetic recording information, with an MR read head element, an asymmetry representing the vertical asymmetry of the output signal waveform, and a bit error rate And there is a correlation between the S / N ratio. Here, the asymmetry Asym (%) of the output signal (reproduction output) is asymmetry (%) = (TAA1−TAA2) / (TAA1 + TAA2) where TAA1 is the positive amplitude of the reproduction output and TAA2 is the negative amplitude. ) × 100 (%). The closer the asymmetry is to zero, the smaller the bit error rate and the smaller the S / N ratio. Therefore, the magnetic head has excellent reproduction characteristics.

  In Patent Document 1, the bias magnetic field applied to the MR element is adjusted by controlling the bias current supplied to the MR element and the bias strip, that is, the sense current so that the asymmetry approaches zero, and the electromagnetic conversion characteristic is linear. A technique for reducing the error rate by operating the MR element in such a region is disclosed.

  This known technique is a technique for controlling the transverse bias magnetic field as in the soft film bias method used in the initial single layer anisotropic magnetoresistive (AMR) head.

JP 2003-228803 A

  However, according to this known technique, since the sense current that directly affects the output of the MR element is adjusted and changed, there is a big problem that the MR output varies from head to head. On the other hand, since the sense current cannot be changed greatly, there is a disadvantage that the error rate cannot be reliably reduced.

  Accordingly, an object of the present invention is to provide a thin film magnetic head, a magnetic head assembly, a magnetic disk drive apparatus, and an asymmetry characteristic compensation method capable of reducing the bit error rate and the S / N ratio without causing variations in MR output. It is to provide.

  According to the present invention, the MR read head element is provided independently of the MR read head element, and the height of the MR read head element is increased by flowing a direct current independent of the sense current of the MR read head element. There is provided a thin film magnetic head comprising magnetic field generating means for generating a DC magnetic field applied in the direction.

  The magnetic field generating means is independently provided outside the MR read head element, and the magnetic field generating means generates a DC magnetic field applied in the height direction of the MR read head element. By applying a DC magnetic field in the height direction of the MR read head element, asymmetry can be brought close to zero, and the bit error rate and the S / N ratio can be reduced. In addition, in this case, since the magnetic field generating means is independently provided outside the MR read head element, an optimum magnetic field can be applied without changing the sense current of the MR read head element, thereby causing variations in MR output. There is nothing.

  The magnetic field generating means is preferably a coil conductor provided behind the MR read head element when viewed from the air bearing surface (ABS).

  It is also preferred that the MR read head element is a tunnel magnetoresistive (TMR) element.

  According to the present invention, there is provided a magnetic head assembly including the above-described thin film magnetic head and a support for supporting the thin film magnetic head. Here, the magnetic head assembly is an assembly in which a composite thin film magnetic head (magnetic head slider) including a write head element and a read magnetic head element and a support mechanism thereof are mechanically and electrically assembled. More specifically, in the case of an assembly of a magnetic head slider and a suspension, it is referred to as a head gimbal assembly (HGA). When a plurality of HAAs are stacked, it is often called a head stack assembly (HSA).

  According to the present invention, there is further provided a magnetic disk drive device comprising the above-described magnetic head assembly and a magnetic recording medium facing the MR read head element of the magnetic head assembly.

  The magnetic disk drive device further comprises current supply means for supplying a direct current to the magnetic field generating means for generating a direct current magnetic field that minimizes the asymmetry of the reproduction output of the MR read head element during at least operation of the MR read head element. It is preferable.

  The current supply means is preferably means for supplying a direct current to the magnetic field generation means only when the MR read head element performs a read operation.

  It is also preferable that the current supply means is means for constantly supplying a direct current to the magnetic field generating means during operation of the magnetic disk drive device.

  The apparatus further comprises means for measuring the asymmetry of the reproduction output of the MR read head element, and based on the asymmetry measured by the current supply means, generates a direct current that minimizes the asymmetry of the reproduction output of the MR read head element. It is also preferable that it is a means for seeking and supplying.

  According to the present invention, furthermore, a thin film magnetic head having an MR read head element, a support for supporting the thin film magnetic head, and a DC magnetic field applied from the outside of the thin film magnetic head in the height direction of the MR read head element. A magnetic head assembly comprising a magnetic field generating means for generating is provided.

  A magnetic field generating means is provided outside the thin film magnetic head, and a DC magnetic field is applied from the magnetic field generating means in the height direction of the MR read head element. By applying a DC magnetic field in the height direction of the MR read head element, asymmetry can be brought close to zero, and the bit error rate and the S / N ratio can be reduced. In this case, since the magnetic field generating means is provided outside the thin film magnetic head, an optimum magnetic field can be applied without changing the sense current of the MR read head element, so that variations in MR output do not occur.

  The MR read head element is preferably a TMR element.

  It is also preferable that the magnetic field generating means is at least one electromagnet for generating a DC magnetic field by flowing a DC current independent of the sense current of the MR read head element.

  It is also preferred that the magnetic field generating means is at least one permanent magnet for generating a DC magnetic field that minimizes the asymmetry of the reproduction output of the MR read head element.

  According to the present invention, there is further provided a magnetic disk drive device comprising the above-described magnetic head assembly and a magnetic recording medium facing the MR read head element of the magnetic head assembly.

  According to the present invention, the magnetic head assembly described above, the magnetic recording medium facing the MR read head element of the magnetic head assembly, and the asymmetry of the reproduction output of the MR read head element at least during the operation of the MR read head element. In order to generate a direct current magnetic field that minimizes the current, a magnetic disk drive device is provided that includes current supply means for supplying a direct current independent of the sense current of the MR read head element to the magnetic field generation means.

  The current supply means is preferably means for supplying a direct current to the magnetic field generating means only when the MR read head element performs a read operation.

  It is also preferable that the current supply means is means for constantly supplying a direct current to the magnetic field generating means during operation of the magnetic disk drive device.

  The apparatus further includes means for measuring the asymmetry of the reproduction output of the MR read head element, and the current supply means generates a DC magnetic field that generates a DC magnetic field that minimizes the asymmetry of the reproduction output of the MR read head element based on the measured asymmetry. It is also preferable that the current is obtained and supplied.

  According to the present invention, furthermore, a magnetic head assembly including a thin film magnetic head having an MR read head element and a support for supporting the thin film magnetic head, a magnetic recording medium facing the MR read head element of the magnetic head assembly, There is provided a magnetic disk drive device comprising magnetic field generating means for generating a DC magnetic field applied from the outside of the thin film magnetic head in the height direction of the MR read head element.

  A magnetic field generating means is provided outside the thin film magnetic head, and a DC magnetic field is applied from the magnetic field generating means in the height direction of the MR read head element. By applying a DC magnetic field in the height direction of the MR read head element, asymmetry can be brought close to zero, and the bit error rate and the S / N ratio can be reduced. In this case, since the magnetic field generating means is provided outside the thin film magnetic head, an optimum magnetic field can be applied without changing the sense current of the MR read head element, so that variations in MR output do not occur.

  The MR read head element is preferably a TMR element.

  It is also preferable that the magnetic field generating means is at least one electromagnet for generating a DC magnetic field by flowing a DC current independent of the sense current of the MR read head element.

  It is also preferred that the magnetic field generating means is at least one permanent magnet for generating a DC magnetic field that minimizes the asymmetry of the reproduction output of the MR read head element.

  Current that supplies a direct current independent of the sense current of the MR read head element to the magnetic field generating means that generates a DC magnetic field that minimizes the asymmetry of the reproduction output of the MR read head element at least during operation of the MR read head element. It is also preferable to further include a supply means.

  The current supply means is preferably means for supplying a direct current to the magnetic field generation means only when the MR read head element performs a read operation.

  It is also preferable that the current supply means is means for constantly supplying a direct current to the magnetic field generating means during operation of the magnetic disk drive device.

  The apparatus further includes means for measuring the asymmetry of the reproduction output of the MR read head element, and the current supply means generates a DC magnetic field that generates a DC magnetic field that minimizes the asymmetry of the reproduction output of the MR read head element based on the measured asymmetry. It is also preferable that the current is obtained and supplied.

  According to the present invention, a DC magnetic field that minimizes the reproduction output asymmetry of the MR read head element is applied from the outside of the MR read head element in the height direction of the MR read head element, at least during operation of the MR read head element. A method for compensating for asymmetry characteristics is provided.

  A DC magnetic field is applied in the height direction from the outside of the MR read head element. By applying a DC magnetic field in the height direction of the MR read head element, asymmetry can be brought close to zero, and the bit error rate and the S / N ratio can be reduced. In addition, in this case, since the j-th order is applied from the outside of the MR read head element, an optimum magnetic field can be applied without changing the sense current of the MR read head element, so that the MR output does not vary.

  It is preferable to measure the asymmetry of the reproduction output of the MR read head element and determine the DC magnetic field based on the measured asymmetry.

  It is also preferable to apply a DC magnetic field only when the MR read head element performs a read operation.

  It is also preferable to always apply a DC magnetic field during operation of the magnetic disk drive device.

  According to the present invention, the magnetic field generating means is independently provided outside the MR read head element, and the magnetic field generating means generates a DC magnetic field applied in the height direction of the MR read head element. By applying a DC magnetic field in the height direction of the MR read head element, asymmetry can be brought close to zero, and the bit error rate and the S / N ratio can be reduced. In addition, in this case, since the magnetic field generating means is independently provided outside the MR read head element, an optimum magnetic field can be applied without changing the sense current of the MR read head element, thereby causing variations in MR output. There is nothing.

  FIG. 1 is a perspective view schematically showing a configuration of a main part of a magnetic disk drive device as one embodiment of the present invention, and FIG. 2 is a perspective view showing a configuration example of the HGA of FIG. FIG. 4 is a perspective view showing a composite thin film magnetic head mounted on the tip of the HGA in FIG. 2, and FIG. 4 shows the magnetic head element portion of the composite thin film magnetic head in FIG. 3 from the element forming surface side of the slider substrate. It is a plan view.

  In FIG. 1, 10 is a plurality of magnetic disks rotating around the rotation axis of a spindle motor 11, 12 is an assembly carriage device for positioning a composite thin film magnetic head (magnetic head slider) on a track, and 13 is thin film magnetic. The read / write operation of the head and the recording / reproducing and current control circuits for controlling the direct current to the direct current magnetic field generating conductor for generating the direct current magnetic field are shown.

  The assembly carriage device 12 is provided with a plurality of drive arms 14. These drive arms 14 are angularly swingable 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 magnetic head slider 21 so as to face the surface of each magnetic disk 10. A single magnetic disk 10, a drive arm 14, and an HGA 17 may be provided in the magnetic disk drive device.

  As shown in FIG. 2, in the HGA, a magnetic head slider 21 having an inductive write head element and a TMR read head element is fixed to the tip of a suspension 20, and a wiring member 25 is connected to a terminal electrode of the thin film magnetic head 21. One end is electrically connected.

  The suspension 20 includes a load beam 22 that generates a load applied to the magnetic head slider 21, an elastic flexure 23 fixed and supported on the load beam 22, and a base plate 24 provided at the base of the load beam 22. And a wiring member 25 which is provided on the flexure 23 and the load beam 22 and is composed of a lead conductor and connection pads electrically connected to both ends thereof.

  Obviously, the structure of the suspension in the magnetic head assembly of the present invention is not limited to the structure described above. Although not shown, a head driving IC chip may be mounted in the middle of the suspension 20.

  As shown in FIGS. 3 and 4, the magnetic head slider 21 in this embodiment includes a composite magnetic head element 32 composed of a TMR read head element 30 and an inductive write head element 31 stacked on each other, and these TMR read head elements. 30 and four signal terminal electrodes 33 and 34 respectively connected to the inductive write head element 31, and two drive terminal electrodes 35 of a DC magnetic field generating conductor for generating a DC magnetic field not shown in FIG. Is provided on the element forming surface 37 which is one side surface when the ABS 36 of the magnetic head slider is used as the bottom surface. Both ends of the DC magnetic field generating conductor are connected to the two drive terminal electrodes 35. In addition, the position of these terminal electrodes is not limited to the form of FIG. In FIG. 3, there are six terminal electrodes, but one end of the DC magnetic field generating conductor is connected to one drive terminal electrode and the other end is grounded to the slider substrate to form five terminal electrodes. Also good.

  FIG. 5 is a central cross-sectional view schematically showing the structure of the composite thin film magnetic head in the present embodiment, and shows a cross section taken along the line VV of FIG.

For example, an ABS 36 facing the surface of the magnetic disk is formed on a slider substrate 50 formed of AlTiC (AlTiC, Al ₂ O ₃ —TiC) or the like. During operation, the magnetic head slider 21 floats hydrodynamically on the surface of the rotating magnetic disk with a predetermined flying height. On the element forming surface 37 of the slider substrate 50, an MR read head element 52 and an inductive write head element 53, which are covered with an insulating material layer 51 and have an MR multilayer including a free layer and a pinned layer, are formed. Yes.

  The MR read head element 52 is preferably a TMR read head element, but has a CPP (Current Perpendicular to Plane) structure in which a sense current flows in a direction perpendicular to the laminated surface or a head structure in which a sense current flows in a direction parallel to the laminated surface. May be a giant magnetoresistive effect (GMR) read head element having a CIP (Current In Plane) structure. The inductive write head element 53 is preferably a write head element having a perpendicular magnetic recording structure, but may be a write head element having a horizontal magnetic recording structure.

  Behind the ABS 36 of the MR read head element 52 is a helical or toroidal coil conductor 54 as a DC magnetic field generating conductor constituting an electromagnet for generating a DC magnetic field, and a magnetic core inserted therethrough. 55 is provided. Both ends of the coil conductor 54 are connected to the drive terminal electrode 35 described above.

  FIG. 6 is a block diagram showing a circuit configuration of the recording / reproducing and current control circuit 13 of the HDD shown in FIG.

  In the figure, reference numeral 60 denotes a recording / reproducing circuit, 61 denotes a current control circuit, and 62 denotes a CPU. The recording / reproducing circuit 60 includes a recording / reproducing channel 60 a and a preamplifier unit 60 b connected to the MR read head element 52 and the inductive write head element 53. The current control circuit 61 includes a register 61 a, a D / A converter 61 b, and a current control unit 61 c connected to the coil conductor 54.

The recording data output from the recording / reproducing channel 60a is supplied to the preamplifier unit 60b. Preamplifier 60b receives a recording control signal outputted from the CPU62 in write gate 60b _1, the recording control signal only when instructing a write operation, flowing a write current according to the recording data to the inductive write head element 53, As a result, recording is performed on the magnetic disk.

Further, only when the reproduction control signal outputted from the CPU62 are received by the read gate 60b ₂ instructs a read operation, a sense current flows from the preamplifier unit 60b to the MR read head element 52. The reproduction signal output from the MR read head element 52 and input to the preamplifier unit 60b via the auto gain controller (AGC) 60b ₃ for stabilizing the output is amplified and demodulated to become reproduction data, which is transmitted to the recording / reproduction channel 60a. Sent.

  The current control unit 61c of the current control circuit 61 receives the ON / OFF signal output from the preamplifier unit 60b and the current value control signal output from the CPU 62 via the register 61a and the D / A converter 61b. When this ON / OFF signal is an ON operation instruction, a drive current flows through the coil conductor 54. The current value is controlled to a value corresponding to the current value control signal.

  In this manner, by providing the current control circuit 61 independently of the recording / reproducing circuit 60, it is possible to use more various energization modes. Furthermore, since the CPU 62 controls the current control circuit 61 and the recording / reproducing circuit 60, the coil conductor 54 can be energized in synchronism with the read operation.

  Obviously, the circuit configuration of the recording / reproducing and current control circuit 13 is not limited to that shown in FIG. The write and read operations may be specified by a signal other than the recording / reproduction control signal.

  FIG. 7 is a flowchart for schematically explaining, in particular, the portion related to the present invention in the control operation of the CPC 62 in the recording / reproducing and current control circuit 13, which is executed when the power is first turned on after the HDD is manufactured. Shows a part of the initialization routine to be performed.

  As shown in the figure, in the initial setting routine, first, the asymmetry Asym of the output signal (reproduction output) of the MR read head element 52 is measured (step S1). Asymmetry Asym (%) is given by Assym (%) = (TAA1−TAA2) / (TAA1 + TAA2) × 100 (%), where TAA1 is the positive amplitude of the reproduction output and TAA2 is the negative amplitude.

  Next, the DC current value of the coil conductor 54 at which the measured asymmetry Asym is closest to zero is obtained (step S2). In order to obtain the direct current value from the asymmetry Asym, the asymmetry Asym when each different direct current is actually applied and different direct magnetic fields (height direction) are applied is measured, and the direct current at which the measured value is closest to zero is measured. The current value may be obtained. Actually, a relational expression in which the value of the DC current to be passed through the coil conductor 54 is determined in advance from the asymmetry Asymme measured in a state where no DC current is passed through the coil conductor 54 and therefore no external magnetic field is applied. Or directly from the table. That is, as shown in FIG. 8, in various MR read head elements, there is a specific relationship between the DC magnetic field in the height direction and the asymmetry Asym, and this relationship is such that the asymmetry Asym is on the positive side. It does not change even if it is shifted or shifted to the negative side. Therefore, if the asymmetry Asym is measured without applying an external magnetic field, the value of the direct current to be applied in order to make the asymmetry Asym zero can be uniquely determined from the value.

  Next, the obtained direct current value is stored as a conductor coil drive current value (step S3).

On the other hand, in the normal operation routine of the HDD, only when the reproduction control signal received by the read gate 60b ₂ instructs a read operation, ON / OFF signals sent from the preamplifier unit 60b to the power control unit 61c is turned on, As a result, the power control unit 61c allows the value of the current value control signal output from the CPU 62 via the register 61a and the D / A converter 61b, that is, a value corresponding to the conductor coil drive current value stored in the initial setting routine, Current is passed through the coil conductor 54.

As a result, a DC magnetic field M _DC is generated from the electromagnet including the coil conductor 54 and the magnetic core 55, and this DC magnetic field M _DC is applied in the height direction of the MR read head element 52.

  As shown in FIG. 9A, when a DC magnetic field is not applied, the magnetization direction Free of the free layer of the MR read head element is parallel to the ABS, and the magnetization direction Pin of the pinned layer is to the ABS. The asymmetry Asym is almost zero when Free and Pin are orthogonal to each other. However, when the magnetization direction Free of the free layer is not parallel to ABS, Asym> 0 or Asym < 0.

Therefore, in such a case, as shown in FIG. 9B or 9C, a DC magnetic field M _{DC in the} height direction (a direction perpendicular to the ABS, a direction parallel to the Pin direction) with respect to the MR read head element. Is applied from the outside of the element, the asymmetry Asym can be made substantially zero.

  There is generally a relationship as shown in FIG. 10 between the asymmetry Asym of the MR read head element and the bit error rate, and it has been found that the bit error rate decreases as the asymmetry Asym approaches zero. Therefore, by applying a DC magnetic field, as shown in FIG. 11, the bit error rate can be further reduced by bringing the asymmetry assembly close to zero.

  As described above, according to the present embodiment, since the DC magnetic field that brings the asymmetry Asym (%) close to zero is applied in the height direction of the MR read head element 52, the bit error rate and S / N ratio are increased. Can be reduced. In this case, since the coil conductor 54 is driven separately from the sense current of the MR read head element 52, an optimum magnetic field can be applied without changing the sense current of the MR read head element 52, and therefore, the MR output varies. Will not cause.

  In the above-described embodiment, the electromagnet is driven to generate a DC magnetic field only when the MR read head element performs a read operation. However, while the HDD is operating, the electromagnet is always driven to generate the DC magnetic field. Obviously, it may be generated.

  In the embodiment described above, a single coil conductor is provided, but it is also clear that a plurality of coil conductors may be provided.

  FIG. 12 is a central cross-sectional view schematically showing the configuration of the composite thin-film magnetic head in a modification of the embodiment of FIGS.

  In this modification, the DC magnetic field generating conductor 124 is made of a single linear conductor provided between the MR read head element 52 and the substrate 50, and no magnetic core is provided. Both ends of the conductor 124 are connected to the drive terminal electrode 35.

  Other configurations in this modification are exactly the same as those in the embodiment shown in FIGS. Accordingly, in FIG. 12, the same reference numerals are used for components that are substantially the same as those in FIG. Further, the operational effects and the like in this modified mode are almost the same as those in the embodiment of FIGS.

  FIG. 13 is a central cross-sectional view schematically showing a configuration of a composite thin film magnetic head in another modification of the embodiment of FIGS.

  In this modification, the DC magnetic field generating conductor 134 is composed of a single linear conductor provided between the MR read head element 52 and the inductive write head element 53, and no magnetic core is provided. . Both ends of the conductor 134 are connected to the drive terminal electrode 35.

  Other configurations in this modification are exactly the same as those in the embodiment shown in FIGS. Accordingly, in FIG. 13, the same reference numerals are used for components that are substantially the same as those in FIG. 5. Further, the operational effects and the like in this modified mode are almost the same as those in the embodiment of FIGS.

  FIG. 14 is a central cross-sectional view schematically showing the configuration of a composite thin film magnetic head in still another modification of the embodiment of FIGS.

  In this modification, the DC magnetic field generating conductor 144 is formed of a single linear conductor provided between the lower shield layer and the MR multilayer film inside the MR read head element 52 '. There is no core. Both ends of the conductor 144 are connected to the drive terminal electrode 35.

  Other configurations in this modification are exactly the same as those in the embodiment shown in FIGS. Therefore, in FIG. 14, the same reference numerals are used for components that are substantially the same as those in FIG. Further, the operational effects and the like in this modified mode are almost the same as those in the embodiment of FIGS.

  FIG. 15 is a perspective view schematically showing a partial configuration excluding the suspension portion of the HGA in another embodiment of the present invention.

  In the present embodiment, no DC magnetic field generating conductor or magnetic core is provided in the composite thin-film magnetic head, and a DC magnetic field is formed in the sheet 150 fixed to the surface opposite to the ABS of the magnetic head slider 21 '. A helical or toroidal coil conductor 154 serving as a DC magnetic field generating conductor constituting an electromagnet for generating a magnetic core and a magnetic core (not shown) inserted therethrough are provided.

  The magnetic head slider 21 'is configured to be fixed to the suspension 20 shown in FIG. Both ends of the coil conductor 154 are connected to the current control circuit 61 of the recording / reproducing and current control circuit 13 via the wiring member 25 of the suspension 20. A DC magnetic field generated from the electromagnet is also applied in the height direction of the MR read head element, as in the case of the above-described embodiments and modifications.

  Other configurations in the present embodiment are the same as those in the embodiment in FIGS. Accordingly, in FIG. 15, the same reference numerals are used for the same components as those in the embodiment of FIGS. The operational effects and the like in this embodiment are substantially the same as those in the embodiment of FIGS. 1 to 11 except that the configuration of the composite thin film magnetic head need not be changed.

  FIG. 16 is a side view schematically showing the configuration of a part of a magnetic disk drive device as a further embodiment of the present invention.

  In this embodiment, the HGA itself is not provided with a DC magnetic field generating conductor or a magnetic core, and an electromagnet 160 that applies a DC magnetic field to the magnetic head slider 21 ′ from the outside of the HGA 17 ′ and the magnetic disk 10 is a magnetic disk drive. It is provided in the apparatus. The electromagnet 160 includes a helical or toroidal coil conductor 164 provided above the HGA 17 ′ when viewed from the magnetic disk 10 and a magnetic core 165 inserted through the coil conductor 164. Both ends of the coil conductor 164 are connected to the current control circuit 61 of the recording / reproducing and current control circuit 13 via a wiring member (not shown). The DC magnetic field generated from the electromagnet 160 is also applied in the height direction of the MR read head element as in the case of the above-described embodiment and modification. The electromagnet 160 may be movable together with the magnetic head slider 21 'so that the electromagnet 160 is always positioned above the magnetic head slider 21'. The electromagnet 160 is provided at a fixed position, and the entire moving range of the magnetic head slider 21 'is provided. Alternatively, a DC magnetic field may be applied.

  Other configurations in the present embodiment are the same as those in the embodiment in FIGS. Therefore, in FIG. 16, the same reference numerals are used for the same components as those in the embodiment of FIGS. The operational effects and the like in this embodiment are substantially the same as those in the embodiment of FIGS. 1 to 11 except that the configuration of the composite thin film magnetic head and the configuration of the HGA need not be changed.

  FIG. 17 is a side view schematically showing the configuration of a part of a magnetic disk drive apparatus as still another embodiment of the present invention.

  In this embodiment, the HGA itself is not provided with a DC magnetic field generating conductor or a magnetic core, and the DC magnetic field is superimposed on the HGA 17 'outside the HGA 17' when viewed from the magnetic disk 10 in the magnetic disk drive device. An application HGA 177 is provided. Each DC magnetic field applying HGA 177 is provided with a DC magnetic field applying electromagnet 170 at the position of the magnetic head slider in the normal HGA 17 ′. Although not shown, the electromagnet 170 is composed of a helical or toroidal coil conductor and a magnetic core inserted therethrough. Both ends of the coil conductor are connected to the current control circuit 61 of the recording / reproducing and current control circuit 13 via a wiring member (not shown). The DC magnetic field generated from the electromagnet 170 is also applied in the height direction of the MR read head element as in the case of the above-described embodiment and modification.

  Other configurations in the present embodiment are the same as those in the embodiment in FIGS. Accordingly, in FIG. 17, the same reference numerals are used for the same components as those in the embodiment of FIGS. The operational effects and the like in this embodiment are substantially the same as those in the embodiment of FIGS. 1 to 11 except that the configuration of the composite thin film magnetic head and the configuration of the HGA need not be changed.

  In the embodiment of FIGS. 15 to 17, an electromagnet is used to apply a DC magnetic field in the height direction of the MR read head element, but the value of the DC magnetic field to be applied does not vary greatly. It is obvious that a permanent magnet that generates an equivalent DC magnetic field may be used instead of the electromagnet. In the case of using a permanent magnet, the asymmetry Asym of the MR read head element is measured, and a permanent magnet that generates a DC magnetic field such that the asymmetry Asymim approaches zero is selected and attached from the measurement result.

  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 of a magnetic disk drive device as one embodiment of the present invention. FIG. It is a perspective view which shows one structural example of HGA of FIG. It is a perspective view which shows the composite type thin film magnetic head with which the front-end | tip part of HGA of FIG. 2 was mounted | worn. FIG. 4 is a plan view of the magnetic head element portion of the composite thin film magnetic head of FIG. 3 as viewed from the element forming surface side of the slider substrate. FIG. 4 is a central sectional view schematically showing a configuration of the composite thin film magnetic head of FIG. 3. FIG. 2 is a block diagram showing a circuit configuration of a recording / reproducing and current control circuit of the HDD shown in FIG. 1. It is a flowchart which roughly illustrates the part relevant to the present invention in the control operation of CPC in the recording / reproducing and current control circuit. It is a figure showing the characteristic of asymmetry Asymm with respect to a DC magnetic field. It is a figure explaining that the asymmetry Asym can be made substantially zero by applying a DC magnetic field in the height direction. It is a figure showing the general characteristic of the bit error rate with respect to asymmetry Assym. It is a figure explaining that a bit error rate falls by making asymmetry Assym close to zero. FIG. 12 is a central cross-sectional view schematically showing a configuration of a composite thin film magnetic head according to a modification of the embodiment of FIGS. FIG. 12 is a central cross-sectional view schematically showing a configuration of a composite thin film magnetic head in another modification of the embodiment of FIGS. FIG. 12 is a central cross-sectional view schematically showing a configuration of a composite thin film magnetic head in still another modification of the embodiment of FIGS. It is a perspective view which shows roughly the one part structure except the suspension part of HGA in other embodiment of this invention. FIG. 5 is a side view schematically showing a partial configuration of a magnetic disk drive device as a further embodiment of the present invention. FIG. 14 is a side view schematically showing a partial configuration of a magnetic disk drive device as still another embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Magnetic disk 11 Spindle motor 12 Assembly carriage apparatus 13 Recording / reproduction and current control circuit 14 Drive arm 15 Voice coil motor (VCM)
16 Pivot bearing shaft 17, 17 ', 177 HGA
20 Suspension 21, 21 'Thin-film magnetic head 22 Load beam 23 Flexure 24 Base plate 25 Wiring member 30, 52, 52' MR read head element 31, 53 Inductive write head element 32 Magnetic head element 33, 34 Signal terminal electrode 35 Drive terminal electrode 36 ABS
37 Element formation surface 50 Slider substrate 51 Insulating material layer 54, 124, 134, 144, 154, 164 Coil conductor 55, 165 Magnetic core 60 Recording / reproducing circuit 60a Recording / reproducing channel 60b Preamplifier part 60b ₁ Write gate 60b ₂ Read gate 60b ₃ Auto gain controller (AGC)
61 Current Control Circuit 61a Register 61b D / A Converter 61c Current Control Unit 62 CPU
150 sheet 160, 170 electromagnet

Claims (30)

  The magnetoresistive effect read head element and the magnetoresistive effect read head element are provided independently of the magnetoresistive effect read head element, and the magnetoresistive effect is obtained by flowing a direct current independent of the sense current of the magnetoresistive effect read head element. A thin film magnetic head comprising: a magnetic field generating means for generating a DC magnetic field applied in the height direction of the read head element.   2. The thin film magnetic head according to claim 1, wherein the magnetic field generating means is a coil conductor provided behind the magnetoresistive read head element as viewed from the air bearing surface.   3. A thin film magnetic head according to claim 1, wherein the magnetoresistive read head element is a tunnel magnetoresistive element.   4. A magnetic head assembly comprising: the thin film magnetic head according to claim 1; and a support that supports the thin film magnetic head.   5. A magnetic disk drive device comprising: the magnetic head assembly according to claim 4; and a magnetic recording medium facing a magnetoresistive read head element of the magnetic head assembly.   Current supply means for supplying to the magnetic field generating means a DC current that generates a DC magnetic field that minimizes the asymmetry of the reproduction output of the magnetoresistive effect read head element during at least operation of the magnetoresistive effect read head element. 6. The magnetic disk drive apparatus according to claim 5, wherein   7. The magnetic disk drive apparatus according to claim 6, wherein the current supply means supplies the direct current to the magnetic field generation means only when the magnetoresistive read head element performs a read operation. .   7. The magnetic disk drive device according to claim 6, wherein the current supply means is means for constantly supplying the direct current to the magnetic field generating means while the magnetic disk drive device is in operation.   Means for measuring the asymmetry of the reproduction output of the magnetoresistive effect read head element, and the current supply means determines the asymmetry of the reproduction output of the magnetoresistive effect read head element to be minimum based on the measured asymmetry. 9. The magnetic disk drive device according to claim 6, wherein the magnetic disk drive device is means for obtaining and supplying a direct current that generates a direct current magnetic field.   A thin film magnetic head having a magnetoresistive effect read head element, a support for supporting the thin film magnetic head, and a DC magnetic field applied from the outside of the thin film magnetic head to the height direction of the magnetoresistive effect read head element are generated. A magnetic head assembly comprising a magnetic field generating means.   11. The magnetic head assembly according to claim 10, wherein the magnetoresistive effect read head element is a tunnel magnetoresistive effect element.   12. The magnetic field generating means is at least one electromagnet for generating the DC magnetic field by flowing a DC current independent of a sense current of the magnetoresistive read head element. The magnetic head assembly described.   12. The magnetism according to claim 10, wherein the magnetic field generating means is at least one permanent magnet for generating a DC magnetic field that minimizes the asymmetry of the reproduction output of the magnetoresistive read head element. Head assembly.   14. A magnetic disk drive apparatus comprising: the magnetic head assembly according to claim 10; and a magnetic recording medium facing a magnetoresistive read head element of the magnetic head assembly.   The magnetic head assembly according to any one of claims 10 to 12, a magnetic recording medium facing the magnetoresistive read head element of the magnetic head assembly, and at least during operation of the magnetoresistive read head element, Current supply for supplying a DC current independent of the sense current of the magnetoresistive read head element to the magnetic field generating means in order to generate a DC magnetic field that minimizes the asymmetry of the reproduction output of the magnetoresistive read head element And a magnetic disk drive device.   16. The magnetic disk drive apparatus according to claim 15, wherein the current supply means is means for supplying the direct current to the magnetic field generation means only when the magnetoresistive read head element performs a read operation. .   16. The magnetic disk drive device according to claim 15, wherein the current supply means is means for constantly supplying the direct current to the magnetic field generating means while the magnetic disk drive device is in operation.   Means for measuring the asymmetry of the reproduction output of the magnetoresistive effect read head element, and the current supply means determines the asymmetry of the reproduction output of the magnetoresistive effect read head element to be minimum based on the measured asymmetry. 18. The magnetic disk drive device according to claim 15, wherein the magnetic disk drive device obtains and supplies a direct current that generates a direct current magnetic field.   A thin film magnetic head having a magnetoresistive effect read head element and a magnetic head assembly including a support for supporting the thin film magnetic head, a magnetic recording medium facing the magnetoresistive effect read head element of the magnetic head assembly, and the thin film magnetism A magnetic disk drive device comprising: magnetic field generating means for generating a DC magnetic field applied from the outside of the head in the height direction of the magnetoresistive read head element.   20. The magnetic disk drive apparatus according to claim 19, wherein the magnetoresistive read head element is a tunnel magnetoresistive effect element.   21. The at least one electromagnet for generating the DC magnetic field by flowing a DC current independent of a sense current of the magnetoresistive effect read head element. The magnetic disk drive device described.   21. The magnetism according to claim 19, wherein the magnetic field generating means is at least one permanent magnet for generating a DC magnetic field that minimizes the asymmetry of the reproduction output of the magnetoresistive read head element. Disk drive device.   A DC current independent of the sense current of the magnetoresistive read head element that generates a DC magnetic field that minimizes the asymmetry of the reproduction output of the magnetoresistive read head element during at least operation of the magnetoresistive read head element. The magnetic disk drive apparatus according to any one of claims 19 to 21, further comprising current supply means for supplying a current to the magnetic field generating means.   24. The magnetic disk drive device according to claim 23, wherein the current supply means is means for supplying the direct current to the magnetic field generation means only when the magnetoresistive read head element performs a read operation. .   24. The magnetic disk drive device according to claim 23, wherein the current supply means is means for constantly supplying the direct current to the magnetic field generating means while the magnetic disk drive device is in operation.   Means for measuring the asymmetry of the reproduction output of the magnetoresistive effect read head element, and the current supply means determines the asymmetry of the reproduction output of the magnetoresistive effect read head element to be minimum based on the measured asymmetry. 26. The magnetic disk drive device according to claim 23, wherein the magnetic disk drive device is means for obtaining and supplying a direct current that generates a direct current magnetic field.   During at least operation of the magnetoresistive effect read head element, a DC magnetic field that minimizes the reproduction output asymmetry of the magnetoresistive effect read head element is applied from the outside of the magnetoresistive effect read head element to the height of the magnetoresistive effect read head element. A method for compensating for asymmetry characteristics, wherein the method is applied in a direction.   28. The compensation method according to claim 27, wherein asymmetry of the reproduction output of the magnetoresistive effect read head element is measured, and the DC magnetic field is determined based on the measured asymmetry.   29. The compensation method according to claim 27, wherein the DC magnetic field is applied only when the magnetoresistive effect read head element performs a read operation. 29. The compensation method according to claim 27 or 28, wherein the DC magnetic field is constantly applied during operation of the magnetic disk drive device.

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