KR100822611B1 - Reproduction head and magnetic disc device - Google Patents

Abstract

A reproducing head comprising: a read element, first and second electrodes provided at both ends of the read element, a ground electrode provided between the first and second electrodes, and a first constant current flowing between the first electrode and the ground electrode; A first constant current circuit and a second constant current circuit for flowing a second constant current between the second electrode and the ground electrode are included. The regeneration head is further connected to the first and second electrodes, and includes a calculation unit for combining the output of the first electrode and the output of the second electrode, and the relationship between the combined value calculated by the calculation unit and the output of the first and second electrodes. Contains a storage unit having an associated table.

Description

Playback heads and magnetic disk units {REPRODUCTION HEAD AND MAGNETIC DISC DEVICE}

The present invention relates to a playhead and a magnetic disk device using the playhead.

In recent years, the floatation amount of the head slider is reduced due to the miniaturization and densification of the magnetic disk device, and very low floatation or contact recording / reproduction in which the slider contacts the recording medium has been required. In addition, in the conventional magnetic induction head, when the circumferential speed (relative speed between the head and the medium) decreases due to the smaller diameter of the magnetic disk, the reproduction output becomes worse. Therefore, in recent years, a magnetoresistive head (MR head) capable of obtaining a large output even at a low circumferential speed without having to rely on the circumferential speed of the regeneration output has been actively developed to become the mainstream of the magnetic head. In addition, magnetic heads using a giant magnetoresistive (GMR) effect are now commercially available.

Due to the high recording density of the magnetic disk device, the recording area of 1 bit is reduced and the magnetic field generated is also reduced. Although the recording density of commercially available magnetic disk devices is around 40 Gbit / in ² , the increase in recording density is about twice the annual rate. For this reason, there is a demand for a reproduction head capable of responding to a smaller magnetic field range and detecting a small external magnetic field change.

Currently, a spin valve magnetoresistive sensor using a spin valve GMR effect is widely used for a magnetic head. The spin valve magnetoresistive sensor includes a free ferromagnetic layer (free layer) in which the direction of magnetization changes according to an external magnetic field, a nonmagnetic conductive layer formed adjacent to the free layer, and a pinned adjacent to the nonmagnetic conductive layer. It has a ferromagnetic layer (pinned layer) and a spin valve magnetoresistive film which is a multilayer film formed adjacent to the pinned layer and comprising an antiferromagnetic layer made of an antiferromagnetic material for fixing the magnetization direction of the pinned layer.

The spin valve magnetoresistive effect film causes a change in resistance due to a change in the relative angles of the magnetization direction of the free layer and the magnetization direction of the pinned layer. When the magnetization directions face the same direction, the resistance value is minimum. This is the maximum. When the magnetoresistive sensor is used for the magnetic head, the magnetization direction of the pinned layer is fixed in the element height direction of the magnetoresistive element, and the element in which the magnetization direction of the free layer is orthogonal to the pinned layer in the state where no external magnetic field is applied. Design generally in the width direction. Accordingly, the resistance of the spin valve magnetoresistive film can be linearly increased or decreased depending on whether the direction of the signal magnetic field from the magnetic recording medium is parallel or antiparallel to the magnetization direction of the pinned layer. This linear resistance change facilitates signal processing of the magnetic disk device.

In the magnetoresistive head, a pair of electrode terminals are disposed in association with the magnetoresistive effect film, and a sense current of a constant current flows from the pair of electrode terminals to the magnetoresistive effect film during operation of the magnetoresistive head. . When the spin valve magnetoresistive head is moved relatively close to the magnetic disk while the sense current flows, the electrical resistance value of the magnetoresistive effect film is changed in accordance with the signal magnetic field from the magnetic disk. A reproduction signal with an output voltage expressed as a product is output.

With the higher recording density of the magnetic disk device, the core width (sense area) of the read device formed between the pair of electrodes is also increasingly minimized, and the manufacturing process for achieving the required core width of the read device is considerably large. It became difficult. For this reason, problems such as low yield and considerable increase in cost have been accumulated.

(Patent Document 1) Japanese Unexamined Patent Publication No. 57-105821

(Patent Document 2) Japanese Unexamined Patent Publication No. 58-98826

(Patent Document 3) Japanese Unexamined Patent Publication No. 6-18057

Accordingly, it is an object of the present invention to provide a reproduction head capable of minimizing the core width of a read device.

Another object of the present invention is to provide a magnetic disk apparatus capable of high speed reproduction of information recorded on a magnetic disk.

According to one aspect of the present invention, there is provided, as a reproduction head, a read element, first and second electrodes provided at both ends of the read element, a ground electrode provided between the first and second electrodes, and the first electrode. A first constant current means for flowing a first constant current between the ground electrode and a second constant current means for flowing a second constant current different from the first constant current between the second electrode and the ground electrode; A computing means connected to a second electrode and combining the output of the first electrode and the output of the second electrode, and a table in which the composite value calculated by the computing means and the output relation of the first and second electrodes are related. There is provided a reproduction head comprising a storage means.

Preferably, the value of the second constant current is twice the value of the first constant current. The computing means includes a preamplifier and an A / D converter.

According to another aspect of the present invention, there is provided a reproduction head comprising: a read element, first and second electrodes provided at both ends of the read element, a ground electrode provided between the first and second electrodes, and the first electrode; First constant current means for flowing a first constant current between the ground electrode, second constant current means for flowing a second constant current different from the first constant current between the second electrode and the ground electrode, and the first and second A reproduction head is provided, which is connected to two electrodes and includes a selector for selecting one of an output of the first electrode and an output of the second electrode in accordance with a track position signal.

According to still another aspect of the present invention, there is provided a reproduction head comprising: a read element, first and second electrodes provided at both ends of the read element, a ground electrode provided between the first and second electrodes, and the first and second values. N middle electrodes provided between the second electrodes (N is a positive integer), a plurality of constant current means for allowing different constant currents to flow between the ground electrode, the first, second electrodes, and the respective intermediate electrodes, Calculation means connected to the first and second electrodes and the intermediate electrodes, and for synthesizing the outputs of the first and second electrodes and the intermediate electrodes, the combined value calculated by the calculation means and the first, Storage means having a table in which the output relationship of the second electrode and each intermediate electrode is related, means for generating a binary signal from an output of the selected intermediate electrode, connected to one of the selected intermediate electrodes, and In the storage means The force, if the resultant value of the same reproducing head according to claim, including determination means for determining the address of the table is provided.

Preferably, the other constant current is an integer multiple of the minimum constant current. Preferably, the computing means comprises a preamplifier and an A / D converter, and the binary signal generating means comprises an A / D converter and an offset voltage application means.

According to another aspect of the present invention, there is provided a magnetic disk apparatus, comprising: a housing, a magnetic disk having a plurality of tracks rotatably housed in the housing, a recording head for recording data with respect to the magnetic disk, and a reproduction for reading the data. A head slider having a head, and an actuator for moving the head slider across the track of the magnetic disk, the reproduction head comprising: a reading element; first and second electrodes provided at both ends of the reading element; A ground electrode provided between the first and second electrodes, first constant current means for flowing a first constant current between the first electrode and the ground electrode, and different from the first constant current between the second electrode and the ground electrode. Second constant current means for flowing a second constant current, and connected to the first and second electrodes, and outputting the output of the first electrode and the output of the second electrode. There is provided a magnetic disk device comprising a calculating means for combining, and a storage means having a table in which the combined value calculated by the calculating means and the output relationship between the first and second electrodes are related.

According to another aspect of the present invention, there is provided a magnetic disk apparatus, comprising: a housing, a magnetic disk having a plurality of tracks rotatably housed in the housing, a recording head for recording data with respect to the magnetic disk, and a reproduction for reading data. A head slider having a head, and an actuator for moving the head slider across the track of the magnetic disk, the reproduction head comprising: a reading element; first and second electrodes provided at both ends of the reading element; Ground electrodes provided between the first and second electrodes, N intermediate electrodes (N is a positive integer) provided between the first and second electrodes, the ground electrode, the first and second electrodes, and the angles A plurality of constant current means for allowing different constant currents to flow between the intermediate electrodes, and connected to the first and second electrodes and the respective intermediate electrodes, the first and second electrodes and Storage means having a calculation means for synthesizing the outputs of the respective intermediate electrodes, a table in which the composite value calculated by the calculation means and the output relations of the first, second electrodes and the respective intermediate electrodes are associated with each other, Connected to one, including means for generating a binary signal from the output of the selected intermediate electrode, and discriminating means for inputting the binary signal into the storage means to determine the address of the table in the case of the same composite value. A magnetic disk device is provided.

1 is a perspective view of a magnetic disk device with the cover removed;

2 is a perspective view of a reproduction head according to the first embodiment of the present invention.

3 shows that the magnetization direction of the free layer is the first case.

4 (a) to 4 (c) are vector synthesis diagrams in which the magnetization direction of the free layer shown in FIG. 3 is the first case.

5 shows that the magnetization direction of the free layer is the second case.

FIG. 6 is a vector synthesis diagram of the second case in which the magnetization direction of the free layer is shown in FIG. 5; FIG.

7 shows that the magnetization direction of the free layer is a third case.

8 is a vector synthesis diagram of the third case in which the magnetization direction of the free layer is shown in FIG.

9 shows that the magnetization direction of the free layer is a fourth case.

10 is a vector synthesis diagram of the case where the magnetization direction of the free layer is the fourth case shown in FIG.

11 is a schematic synthesis diagram of a first playback system of a playback head of the first embodiment.

12 is a schematic synthesis diagram of a second playback system of the playback head of the first embodiment;

The perspective view of the reproduction head of 2nd Embodiment of this invention.

14 shows that the magnetization direction of the free layer is the first case.

FIG. 15 is a vector synthesis diagram of the case where the magnetization direction of the free layer is the first case shown in FIG.

16 shows that the magnetization direction of the free layer is the second case.

FIG. 17 is a vector synthesis diagram of the second case in which the magnetization direction of the free layer is shown in FIG. 16; FIG.

18 shows that the magnetization direction of the free layer is the third case.

FIG. 19 is a vector synthesis diagram of the third case in which the magnetization direction of the free layer is shown in FIG. 18; FIG.

20 shows that the magnetization direction of the free layer is the fourth case.

FIG. 21 is a vector synthesis diagram of the fourth case in which the magnetization direction of the free layer is shown in FIG. 20; FIG.

Fig. 22 is a schematic synthesis diagram of a regeneration system of the reproducing head of the second embodiment.

Referring to FIG. 1, there is shown a perspective view of a magnetic disk device with the cover removed. A shaft 4 is fixed to the base 2, and a spindle hub (not shown) that is rotationally driven by a DC motor is provided around the shaft 4. The magnetic disk 6 and the spacer (not shown) are alternately inserted into the spindle hub, and the plurality of magnetic disks 6 are predetermined by fastening the disk clamp 8 to the spindle hub by the plurality of screws 10. It is attached to the spindle hub spaced apart.

Reference numeral 12 denotes a rotary actuator composed of an actuator arm assembly 14 and a magnetic circuit 16. The actuator arm assembly 14 is rotatably attached around the shaft 18 fixed to the base 2. The actuator arm assembly 14 includes an actuator block 20 rotatably attached around the shaft 18 via a pair of bearings, and a plurality of actuator arms 22 extending in one direction from the actuator block 20. And a head assembly 24 fixed to the distal end of each actuator arm 22.

Each head assembly 24 supports a head slider 26 having an electronic transducer (magnetic head element) for recording / reading data to and from the magnetic disk 6, and supports the head slider 26 at the distal end thereof. It includes a suspension 28 fixed to the actuator arm 22. A coil (not shown) is supported on the side opposite to the actuator arm 22 with respect to the shaft 18, the coil is inserted into the gap of the magnetic circuit 16, and a voice coil motor (VCM) 30 is constructed. Reference numeral 32 shows a flexible printed wiring board FPC for supplying a recording signal to the electronic transducer or taking out a read signal from the electronic transducer, one end of which is fixed to the side of the actuator block 20.

2, there is shown a perspective view of a reproducing head 2 of the first embodiment of the present invention. The reproduction head 2 includes a pair of electrodes 8 and 10 provided on both sides of the reading element 4 such as a spindle hub magnetoresistive element and a ground electrode 6 provided between the electrodes 8 and 10. have. The first constant current (sense current) flows between the electrode 8 and the ground electrode 6 by the constant current circuit 12. In addition, a second constant current (sense current) flows between the electrode 10 and the ground electrode 6 by the constant current circuit 14. In this embodiment, the second constant current is twice the first constant current. The regeneration head 2 of the present embodiment divides the regeneration head X between the electrode 10 and the ground electrode 6 by providing a ground electrode 6 between the pair of electrodes 8 and 10. The reproduction head Y can be partitioned between the 8 and the ground electrode 6, and the core width of the reproduction head can be minimized to 1/2 or less as compared with the conventional art.

FIG. 3 shows a first case of the magnetization directions of the pinned layer 16 and the free layer 22 of the reproducing head 2 of the first embodiment. The magnetization directions 18 and 20 of the pinned layer 16 are fixed to the element height direction in both the head X and Y. The magnetization direction of the free layer 22 is affected by the signal magnetic field recorded on the magnetic disk, and changes in the right direction or the left direction with respect to the straight line 25 parallel to the width direction of the read element 4.

In the present embodiment, since the sense current flows in the counterclockwise direction to the head X, and the sense current flows in the clockwise direction to the head Y, the magnetization direction 24a in the right direction is defined as "0" for the head X. , The magnetization direction 24b in the left direction is defined as "1". On the other hand, about the head Y, the magnetization direction 26a of the left direction is defined as "0", and the magnetization direction 26b of the right direction is defined as "1". Therefore, in the first case shown in Fig. 3, the binary values of the heads X and Y are 0 and 1, respectively.

4 (a) to 4 (c) show a vector synthesis method in the magnetization directions 24a and 26b in which the magnetization direction of the free layer 22 shown in FIG. 3 is the first case. As an example, the inclination angle θ = 30 ° in the magnetization direction of the free layer 22 will be described. The magnitudes of the magnetizations of the heads X and Y of the pinned layer 16 will be described as 1 and the magnitudes of the magnetizations of the heads X and Y of the free layer 22 as 2 and 1, respectively.

First, as shown in Fig. 4A, parallelograms are created in the magnetization directions 18 and 24a of the pinned layer 16 and the free layer 22 of the head X. The diagonal of this parallelogram becomes the output of head X. Next, as shown in Fig. 4B, the magnetization direction 26b of the free layer 22 of the head Y is the same direction as the magnetization direction 24a of the free layer 22 of the head X. Take the magnetization direction 26b on the extension line of the direction 24a, create a parallelogram in this magnetization direction 26b and the magnetization direction 20 of the pinned layer 16, and make the diagonal the output of the head Y. . Finally, as shown in Fig. 4C, parallel yarn deformation is created using the vectors X and Y, and the diagonal Z becomes the combined output of the reproduction head 2.

5 shows that the magnetization direction of the free layer 22 is the second case. That is, since the magnetization direction 24a of the free layer 22 of the head X is the right direction, the binary value is "0", and the magnetization direction 26a of the free layer 22 of the head Y is the left direction. , The binary value is "0". FIG. 6 shows a vector synthesizing method in the case where the magnetization direction of the free layer 22 is the second case shown in FIG. 5.

7 shows that the magnetization direction of the free layer 22 is the third case. That is, since the magnetization direction 24b of the free layer 22 of the head X is the left direction, the binary value is "1", and the magnetization direction 26b of the free layer 22 of the head Y is the right direction. , The binary value is "1". FIG. 8 shows a vector synthesizing method in the case where the magnetization direction of the free layer 22 is the third case shown in FIG.

9 shows that the magnetization direction of the free layer 22 is the fourth case. That is, since the magnetization direction 24b of the free layer 22 of the head X is the left direction, since its binary value is "1" and the magnetization direction 26a of the free layer 22 of the head Y is the left direction, The binary value is "0". FIG. 10 is a diagram illustrating a vector synthesizing method in the case where the magnetization direction of the free layer 22 is the fourth case shown in FIG. 9.

Table 1 shows the relationship between the signal outputs of the heads X and Y described above and the synthesized output Z (the length of the vector).

TABLE 1

Referring to Fig. 11, a schematic structural diagram of a signal reproducing system of the reproducing head 2 of the first embodiment is shown. The core width (sense area) of the head X is set narrower than the width of the track 28a, and the core width (sense area) of the head Y is set narrower than the width of the track 28b. The outputs of the electrodes 8, 10 are input to the calculation unit 30, and the vector combining operation is executed in this calculation unit 30. The calculating unit 30 includes a preamplifier 32 and an A / D converter 34 for converting the analog signal amplified by the preamplifier 32 into a digital signal.

In the RAM 36, the relationship between the composite value calculated by the calculation unit 30 and the outputs of the electrodes 8 and 10 is stored in association with each other as shown in Table 1. Therefore, by inputting the vector value synthesized by the calculation unit 30 into the RAM 36, the signal output of the heads X and Y can be discriminated from Table 1.

Referring to Fig. 12, there is shown a schematic structural diagram of another embodiment of a signal reproducing system. In the present embodiment, the output of the electrode 8 is input to the preamplifier 40, and the output of the electrode 10 is input to the preamplifier 38. By connecting the preamplifiers 38 and 40 to the selector 42 and selecting the output of the head X or the head Y by the selector 42 in accordance with the track position signal from the servo control system, the two heads are time-series. The signal can be reproduced by X and Y. The output of the selector 42 is converted into a digital signal by the A / D converter 44. In this embodiment, it is not necessary to perform the vector synthesis operation in the calculation unit 30 as in the embodiment shown in FIG. 11, but requires two preamplifiers 38 and 40.

Referring to Fig. 13, there is shown a perspective view of a reproducing head 2A according to a second embodiment of the present invention. In the reproduction head 2A of the present embodiment, two intermediate electrodes 46 and 48 are disposed between the electrode 10 and the ground electrode 6 in addition to the electrodes 8 and 10 and the ground electrode 6 on both sides. It is inserted between the electrode 8 and the ground electrode 6 to provide substantially four reproduction heads X1 to X4.

Although not particularly shown, a first constant current sense current flows between the intermediate electrode 48 and the ground electrode 6, and a second constant current is provided between the intermediate electrode 46 and the ground electrode 6. The sense current which is a 2nd constant current different from a 1st constant current flows by means. Preferably, the second constant current is twice the first constant current. Similarly, a third constant current sense current flows between the electrode 8 and the ground electrode 6, and a fourth constant current means is connected between the electrode 10 and the ground electrode 6 by the fourth constant current means. The sense current which is a constant current flows. Preferably, the third constant current is three times the first constant current, and the fourth constant current is four times the first constant current.

FIG. 14 shows the first case of the magnetization direction of the pinned layer 16 and the magnetization direction of the free layer 22 in the reproduction head 2A. The magnetization direction of the pinned layer 16 is fixed in the height direction of the reading element 4 similarly to the first embodiment. In the reproduction head 2A of the present embodiment, the sense current flows in the counterclockwise direction in the heads X1 and X2, and the sense current flows in the clockwise direction in the heads X3 and X4. Therefore, for the heads X1 and X2, the magnetization direction in the right direction is defined as "0" and the magnetization direction in the left direction is defined as "1" with respect to the straight line 53 parallel to the width direction of the reading element 4. . For the heads X3 and X4, the magnetization direction in the left direction is defined as "0" with respect to the straight line 53, and the magnetization direction in the right direction is defined as "1". Therefore, in the first case shown in FIG. 14, the magnetization direction 52a of the head X1 is "0", the magnetization direction 54a of the head X2 is "0", and the magnetization direction 56b of the head X3 is "0". 1 ", the magnetization direction 58b of the head X4 becomes" 1 ".

FIG. 15 shows a vector combining method of the outputs of the heads X1 to X4 in the case where the magnetization direction of the free layer 22 shown in FIG. 14 is the first case. In the present embodiment, the angle θ = 30 ° formed by the magnetization direction of the free layer 22 and the straight line 53 is set, and the magnetization size of the pinned layer 16 is 2 and the free layer 22 with respect to the heads X1 to X4. The magnetization sizes of are plotted as 4, 2, 1, and 3, respectively. When the magnetization direction of the free layer 22 shown in FIG. 14 is the first, the synthesized output Z can be obtained from FIG. 15.

FIG. 16 shows that the magnetization direction of the free layer 22 in the reproduction head 2A is the second case. In this second case, the magnetization direction 52a of the head X1 is "0", the magnetization direction 54a of the head X2 is "0", and the magnetization direction 56a of the head X3 is "0" and the head X4 The magnetization direction 58a becomes "0". When the magnetization direction of the free layer 22 shown in FIG. 16 is the second case, the combined output Z can be obtained by the vector combining method shown in FIG.

18 shows that the magnetization direction of the free layer 22 is the third case. In this case, the magnetization direction 52a of the head X1 is "0", the magnetization direction 54b of the head X2 is "1", the magnetization direction 56b of the head X3 is "1", and the magnetization direction of the head X4 ( 58a) becomes " 0 ". When the magnetization direction of the free layer 22 shown in FIG. 18 is the third case, the combined output Z can be obtained by the vector combining method shown in FIG.

20 shows that the magnetization direction of the free layer 22 is the fourth case. That is, the magnetization direction 52a of the head X1 is "0", the magnetization direction 54a of the head X2 is "0", the magnetization direction 56b of the head X3 is "1", and the magnetization direction 58a of the head X4. ) Becomes "0". When the magnetization direction of the free layer 22 shown in FIG. 20 is the fourth case, the combined output Z can be obtained by the vector combining method shown in FIG.

Similarly, the combined output Z can be obtained with respect to the 16 magnetization directions of the free layer 22, and the results are shown in Table 2. The composite output Z represents the length of the vector or the magnitude of the output level.

From Table 2, it can be seen that there are five types of cases where the magnitude of the output level Z becomes the same value. Therefore, in order to obtain the signal outputs of the respective heads X1 to X4, it is necessary to distinguish the cases where these synthesized outputs Z are the same.

Referring to Fig. 22, a schematic configuration diagram of the regeneration system of the reproducing head 2A of the second embodiment is shown. The reproduction heads 2A are arranged so that the heads X1 to X4 read the recording information of the tracks 60a to 60d, respectively. The outputs of the electrodes 8, 10 and the intermediate electrodes 46, 48 are input to the calculation unit 30, and a vector calculation is performed in the calculation unit 30 to synthesize these outputs. The calculating unit 30 includes a preamplifier 32 and an A / D converter 34. In the RAM 36, the composite value calculated by the calculation unit 30 and the output relation of the electrodes 8, 10, 46, 48 are stored in association with each other as shown in Table 2.

In the reproduction system of the present embodiment, in the case of the same synthesized output Z shown in Table 2, in order to determine the signal output of each head X1 to X4, the output of the head X3, that is, the output of the intermediate electrode 48 is converted to the preamplifier 62. ), And the analog signal amplified by the preamplifier 62 is input to the binary signal generating unit 64. In the binary signal generation unit 64, the analog signal is converted into a digital signal by the A / D converter 66. The output of the A / D converter 66 is shown in Table 2 as Z1 (X3). Accordingly, by adding the offset voltage 68, that is, -1.74 V to Z1 (X3) by the adder 70, data "0.00" and "0.91" can be obtained. This data is rounded and added to the RAM 36 as addresses of "0" and "l". By dividing the overlapping synthesized output Z by this address in the RAM 36, the overlapping synthesized output Z can be determined.

According to the present invention, a reproduction head capable of minimizing the core width of the read device can be provided. Therefore, it is possible to provide a disk device capable of high-speed reproduction of information recorded on a magnetic disk.

Claims (10)

As a playhead, A reading element; First and second electrodes provided at both ends of the reading element; A ground electrode provided between the first and second electrodes; First constant current means for flowing a first constant current between the first electrode and the ground electrode; Second constant current means for flowing a second constant current different from the first constant current between the second electrode and the ground electrode; Computing means connected to said first and second electrodes and combining the output of said first electrode and the output of said second electrode; Storage means having a table in which a composite value calculated by said calculation means and an output relationship of said first and second electrodes are related; Including; The value of the second constant current is twice the value of the first constant current, Playhead. delete A reproduction head as claimed in claim 1, wherein said calculating means comprises a preamplifier and an A / D converter. As a playhead, A reading element; First and second electrodes provided at both ends of the reading element; A ground electrode provided between the first and second electrodes; First constant current means for flowing a first constant current between the first electrode and the ground electrode; Second constant current means for flowing a second constant current different from the first constant current between the second electrode and the ground electrode; A selector connected to the first and second electrodes for selecting one of an output of the first electrode and an output of the second electrode in accordance with a track position signal; Regeneration head comprising a. As a playhead, A reading element; First and second electrodes provided at both ends of the reading element; A ground electrode provided between the first and second electrodes; N intermediate electrodes (N is a positive integer) provided between the first and second electrodes; A plurality of constant current means for flowing different constant currents between the ground electrode, the first and second electrodes, and the respective intermediate electrodes; Computing means connected to the first and second electrodes and the intermediate electrodes, and for combining the outputs of the first and second electrodes and the intermediate electrodes; Storage means having a table in which a combined value calculated by said calculating means and output relations of said first, second electrodes and said intermediate electrodes are associated; Means for generating a binary signal from an output of the selected intermediate electrode connected to one of the selected intermediate electrodes; Discriminating means for inputting said binary signal into said storage means to determine the address of said table in the case of the same composite value; Play head comprising a. 6. The regeneration head as claimed in claim 5, wherein the other constant current is an integer multiple of a minimum constant current. 6. The reproduction head of claim 5, wherein the calculating means includes a preamplifier and an A / D converter. A reproduction head according to claim 5, wherein said binary signal generating means includes an A / D converter and an offset voltage applying means. As a magnetic disk device, A housing; A magnetic disk having a plurality of tracks rotatably received in the housing; A head slider having a recording head for recording data with respect to the magnetic disk and a reproduction head for reading data; Actuator to move the head slider across the track of the magnetic disk Including; The play head, A reading element; First and second electrodes provided at both ends of the reading element; A ground electrode provided between the first and second electrodes; First constant current means for flowing a first constant current between the first electrode and the ground electrode; Second constant current means for flowing a second constant current different from the first constant current between the second electrode and the ground electrode; Computing means connected to said first and second electrodes and combining the output of said first electrode and the output of said second electrode; Storage means having a table in which a composite value calculated by said calculation means and an output relationship of said first and second electrodes are related; Magnetic disk device comprising a. As a magnetic disk device, A housing; A magnetic disk having a plurality of tracks rotatably received in the housing; A head slider having a recording head for recording data with respect to the magnetic disk and a reproduction head for reading data; Actuator to move the head slider across the track of the magnetic disk Including; The play head, A reading element; First and second electrodes provided at both ends of the reading element; A ground electrode provided between the first and second electrodes; N intermediate electrodes (N is a positive integer) provided between the first and second electrodes; A plurality of constant current means for flowing different constant currents between the ground electrode, the first and second electrodes, and the respective intermediate electrodes; Computing means connected to the first and second electrodes and the intermediate electrodes, and for combining the outputs of the first and second electrodes and the intermediate electrodes; Storage means having a table in which a combined value calculated by said calculating means and output relations of said first, second electrodes and said intermediate electrodes are associated; Means for generating a binary signal from an output of the selected intermediate electrode connected to one of the selected intermediate electrodes; And a discriminating means for inputting said binary signal into said storage means and discriminating an address of said table in the case of a same composite value.

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