JP2001006133A - Magnetic head evaluating method and inspecting device and magnetic disk device equipped with magnetic head evaluating function - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for evaluating a magnetic head for detecting the magnetic pole inversion of the fixed layer of a head element, and a method for manufacturing the magnetic head including the evaluating process of the magnetic head, and an inspecting device and a magnetic disk device equipped with the magnetic head evaluating function. SOLUTION: In this method for evaluating a magnetic head, a recording pattern in which a time interval T1 from a positive pulse to a negative pulse and a time interval T2 shorter than the time interval T1 from a negative pulse to a positive pulse are made different is recorded in a recording medium, and the time interval T2 is subtracted from the time interval T1 of reproduced waveform obtained by reproducing the recording pattern from the recording medium, and when the value of this (T1-T2) is negative, it is judged and evaluated that the magnetizing direction of the fixed layer of a GMR element is inverted. Also, it is possible to provide an inspecting device and a magnetic disk device to which the magnetic head evaluating method is applied.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for evaluating a magnetic head, an inspection apparatus having the function of evaluating a magnetic head, and a magnetic disk drive, and more particularly to detecting magnetic reversal of a fixed layer of a GMR head. The present invention relates to a magnetic head evaluation method, an inspection device, and a magnetic disk device that can perform the method.

[0002]

2. Description of the Related Art Generally, as shown in FIG. 3, a magnetic disk drive comprises a plurality of recording media 1 stacked so as to be driven to rotate, and a plurality of recording media 1 positioned on the recording media 1 for recording and reproducing data. Magnetic head 2 and recording medium 1
An actuator 3 rotatably moves on the recording medium 1, and the actuator 3 positions the magnetic head 2 on an arbitrary track on the recording medium 1 in a state where the recording medium 1 is rotationally driven to perform data recording and reproduction. Is configured.

As shown in FIG. 4, the magnetic head 2 includes a slider 5 on which a magnetic head element 6 is mounted at one end and a spring 4 for elastically supporting the slider 5, and a recording medium 1 which rotates at high speed. The slider 5 is floated at intervals of several tens of nanometers by aerodynamic action to record and reproduce data. In recent years, with the miniaturization and large capacity of magnetic disk devices, higher reproduction sensitivity has been required. Is required.

Therefore, a magnetic head in recent years employs an MR head (magneto resistive head) using a magnetic resistance effect. As shown in FIG. 5, the MR head includes a coil 8 and a magnetic core 9, and includes an inductive recording head element 7 for recording a signal on a recording medium, an MR film 11 for reproducing data, and a reproducing electrode 12. And an MR head element provided.

In this MR head, the thickness of the MR film 11 is 2
As thin as 0 nm, ESD (electrostatic d)
ischage (electrostatic discharge).
This withstand voltage is a low value of about 40 V for the MR head, whereas the withstand voltage of the previous inductive type thin film head is about 100 V or higher. It can be said that the electronic device is very sensitive to ESD.

On the other hand, it has been known that the MR head has two destruction modes due to the above-mentioned ESD and EOS (Electro over stress: high voltage load). 1
One is that heat is generated by high-voltage discharge or high current, which results in physical destruction. This physical destruction is caused by melting of the MR element itself due to rapid heat generation, accompanied by abnormal increase or decrease in the resistance value, and can be detected by abnormality in the external shape. In addition, discharge breakdown due to a high electric field is accompanied by abnormal increase or decrease in resistance value, and can be detected by abnormality in external shape.

Another mode of destruction is magnetic destruction caused by a magnetic field due to a high current. This is a phenomenon in which the magnetic stability of the MR film is destroyed by the magnetic field due to the high current, and no physical destruction occurs, but a magnetic domain is formed. This magnetic destruction does not involve resistance change or shape abnormality,
It appears as an abnormality in the reproduction waveform of the MR element, for example, as an instability in the reproduction waveform or an abnormality in the amplitude on the positive and negative sides.

[0008] When such magnetic destruction occurs, the magnetic head cannot detect data accurately, causing an error in the data, a servo signal cannot be reproduced, and positioning cannot be performed.

As a method for solving the magnetic destruction according to the prior art, it has been proposed to re-magnetize the MR element of the magnetic head again and to restore the original magnetic characteristics by performing initialization.

[0010]

In recent years, in response to a further increase in recording density, a GMR head (Giant head) using a GMR element having higher reproduction sensitivity in place of the MR element shown in FIG. This GMR element using the MR head) has a fixed layer 15, a free layer 14, and an antiferromagnetic layer 16 as shown in FIG. 6, and the free layer 15 and the free layer 15 as shown in FIG. When the magnetization direction with the layer 14 is in the opposite direction, the resistance value increases and the output becomes positive, and when the magnetization direction is in the same direction, the resistance decreases and the output becomes negative as shown in FIG. 6B.

The fixed layer 15 is oriented in a direction perpendicular to the track width direction where the signal magnetic flux comes from the recording medium by exchange coupling by the antiferromagnetic layer 16, and the free layer 14 is disposed on both sides thereof. Since the permanent magnets for controlling the magnetic domains are oriented in the direction perpendicular to the direction in which the signal magnetic flux from the recording medium comes in the same direction as the track width direction, the fixed layer 1
The magnetization direction 5 is important in determining the positive and negative polarities of the output waveform.

The ESD withstand voltage of this GMR element is 10 to 30 V, which is lower than that of the MR head. In particular, due to heat generated by a high current due to ESD and a high magnetic field, as shown in FIG. Reversed from the normal direction, FIG.
As shown in (b), it has the characteristic of turning in the opposite direction. In other words, the GMR element has a characteristic that the relationship between the magnetization directions of the fixed layer and the free layer is reversed due to the ESD and the direction of the magnetic field from the recording medium is the same, so that the polarity of the reproduced waveform is normally reversed. .

FIG. 8 shows the relationship between the applied magnetic field and the reproduction output. As described above, in the GMR element, when the magnetization direction of the fixed layer 15 is reversed due to the ESD, the polarity of the reproduction output becomes completely opposite as shown from the characteristic A to the characteristic B shown in FIG. Therefore, during the process of manufacturing or assembling the magnetic head, E
When SD occurs and the fixed layer is reversed, the positive and negative polarities of the output waveform are reversed, and the conventional inspection method only measures the magnitude of the reproduction amplitude, and cannot detect the reversed polarity. There was a problem that said.

Further, when a magnetic head having a GMR element whose polarity is reversed is assembled in a magnetic disk drive, the polarity of a reproduction signal is reversed in the device, and a data signal or a servo signal is erroneously generated.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the disadvantages of the prior art, and to evaluate a magnetic head capable of detecting a magnetic pole reversal of a fixed layer of a head element, and an evaluation of the magnetic head. It is an object of the present invention to provide a method of manufacturing a magnetic head including a process, an inspection apparatus having the magnetic head evaluation function, and a magnetic disk drive.

[0016]

According to the present invention, there is provided a method for evaluating a magnetic head having a head element including a fixed layer, comprising the steps of: A recording pattern having a different time interval from a pulse to a recording medium is recorded on a recording medium, and a time interval from the positive pulse to the negative pulse and a time interval from the negative pulse to the positive pulse of a reproduced waveform obtained by reproducing the recording pattern from the recording medium. And evaluating the reversal of the magnetization direction of the fixed layer of the head element based on the difference between the two time intervals. In this magnetic head evaluation method, Is a time interval between the negative pulse and the positive pulse, a time interval T2 shorter than the time interval T1, and a value obtained by subtracting the time interval T2 from the time interval T1. Magnetization direction of the pinned layer of the head element when the negative and the second, characterized in that to evaluate the inverted.

Further, the present invention provides a recording medium, a spindle motor for driving the recording medium to rotate, a data recording / reproducing circuit for recording / reproducing data on / from the recording medium using a magnetic head for evaluation, and controls these. In a magnetic head evaluation device comprising a control circuit and evaluating a magnetic head equipped with a head element including a fixed layer, the data recording / reproducing circuit includes a time interval from a positive pulse to a negative pulse and a negative pulse. A recording pattern having a time interval different from the positive pulse is recorded on a recording medium, and the recording pattern is reproduced from the recording medium to obtain a reproduction waveform, and the control circuit controls the reproduction waveform from the positive pulse to the negative pulse. Comparing the time interval of the head pulse with the time interval from the negative pulse to the positive pulse, and evaluating the reversal of the magnetization direction of the fixed layer of the head element based on the difference between the two time intervals. Wherein the data recording / reproducing circuit sets the time interval from the positive pulse to the negative pulse to T1, and sets the time interval from the negative pulse to the positive pulse to the time. Interval T1
A recording pattern having a shorter time interval T2 is recorded on a recording medium, and the control circuit determines that the magnetization direction of the fixed layer of the head element has been reversed when the value obtained by subtracting the time interval T2 from the time interval T1 is negative. Evaluation is a fourth feature.

Further, the present invention provides a recording medium, a spindle motor for driving the recording medium to rotate, a magnetic head on which a head element including a fixed layer is mounted, and recording and reproducing of data on the recording medium by the magnetic head. A data recording / reproducing circuit to perform;
In a magnetic disk drive comprising a control circuit for controlling these, the data recording / reproducing circuit determines a time interval T1 from a positive pulse to a negative pulse and a time interval T2 from a negative pulse shorter than the time interval T1 to a positive pulse. The recording pattern is recorded on a recording medium, and the recording pattern is reproduced from the recording medium to obtain a reproduction waveform. When the control circuit determines that the value obtained by subtracting the time interval T2 from the time interval T1 is negative, the head A fifth feature is that it is determined that the magnetization direction of the fixed layer of the element has been reversed.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a method for evaluating a magnetic head according to an embodiment of the present invention, a method for manufacturing a magnetic head including an evaluation process for the magnetic head, and an inspection having the above-described magnetic head evaluation function will be described. The device and the magnetic disk device will be described in detail with reference to the drawings.

FIG. 1 is a diagram for explaining the principle of a method for evaluating a magnetic head according to the present invention, and shows an inspection apparatus having a magnetic disk device / magnetic head evaluation function (hereinafter referred to as "magnetic head evaluation"). FIG. 3 is a diagram showing a relationship between a recording current waveform applied to the method and the like and a magnetization state or a reproduction waveform of a recording medium (magnetic disk).

The magnetic head evaluation method according to the present embodiment is, as shown in FIG. 1, first, at the time of signal recording, a time interval between a positive pulse and a negative pulse and a time interval between a negative pulse and a positive pulse on a recording medium. Record data using different recording current waveforms. That is, recording is performed using a current waveform in which the switching time of the recording current waveform is asymmetric, specifically, the time interval T1 from the positive pulse to the negative pulse and the time interval T2 from the negative pulse to the positive pulse are shorter than the time interval T1. The recording is performed as a black line when the magnetization state of the medium is high, and as a white line when the magnetization state is low. Next, in the magnetic head evaluation method, the asymmetrically recorded signal is reproduced using a GMR head. This reproduction waveform becomes a positive pulse when the free layer faces upward by the magnetic flux from the recording medium and becomes antiparallel to the direction of the fixed layer. This is because the GMR effect increases the resistance of the GMR element. When the free layer faces downward due to the magnetic flux from the recording medium and becomes parallel to the fixed layer, a negative pulse is generated. This is because the resistance of the element becomes low due to the GMR effect.

Next, the evaluation method measures a time interval T1 from the positive pulse to the negative pulse and a time interval T2 from the negative pulse to the positive pulse. If the GMR head is normal,
Asymmetry of the time interval T1-T2 (T1-T2)
2) is a value larger than 0.

However, if ESD occurs during the process of manufacturing or assembling the magnetic head and the fixed layer is reversed, the positive and negative polarities of the output waveform are reversed, and the magnetization direction of the fixed layer is reversed. Then, the positive and negative polarities are reversed. For this reason, the reproduced waveform at the time of the occurrence of ESD has asymmetry (T1′−) of the time interval T1 ′ (= T2) from the positive pulse to the negative pulse and the time interval T2 ′ (= T1) from the negative pulse to the positive pulse. T2 ') is smaller than 0.

The evaluation method of the magnetic head according to the present invention is as follows.
The time interval T1 from the positive pulse to the negative pulse and the time interval T2 from the negative pulse to the positive pulse are measured, and it is determined whether the asymmetry value is positive or negative.
This is to evaluate whether D has occurred. In the magnetic disk drive according to the present invention, the evaluation process is added to the control program of the actual device itself, and the evaluation is performed at an idle time other than data recording / reproduction, for example, at every predetermined driving time, and
When the occurrence of D is detected, processing such as warning of an error or prompting a recovery process is performed, and the inspection apparatus for a magnetic head according to the present invention similarly evaluates the presence / absence of ESD by adding the evaluation step to the magnetic head manufacturing process. Is what you do.

Next, the algorithm of the magnetic head evaluation method according to the embodiment will be described with reference to FIG. The algorithm comprises a time interval T1 from the asymmetric positive pulse to the negative pulse and a time interval T1 from the negative pulse to the positive pulse.
The recording signal is recorded on a recording medium using the second recording pattern 201, and the recorded signal is reproduced by a GMR head to be evaluated to obtain a reproduced waveform 202. Next, from the reproduction waveform 202, a time interval T1 (reference numeral 20) from a positive pulse to a negative pulse.
4) and the time interval T2 (reference numeral 205) from the negative pulse to the positive pulse and the waveform amplitude E (reference numeral 206) are measured, and the GMR is calculated based on the time interval T1 / T2 and the waveform amplitude E using the algorithm 207 described above. It is determined whether ESD has occurred in the head.

As shown in the figure, the algorithm 207 applies ES to the GMR head when the interval T1−interval T2> 0, the amplitude E> E0, and the read (R) is successful (OK).
It is determined that D has not occurred, and interval T1-interval T2>
0, amplitude E <E0, and read (R) succeeds (O
In the case of K), ESD occurs and the GMR element determines the fixed layer inversion 211, and when the interval T1−interval T2> 0, the amplitude E <E0, and the read (R) is unsuccessful (NG), the ESD occurs. Does not occur, but it is determined that an error (NG) has occurred due to a read error, and the interval T1−interval T2 = 0,
In addition, when the read (R) is successful (OK), ESD occurs and the GMR element determines that the fixed layer is inverted 211, and the interval T
1-Interval T2 = 0 and read (R) is unsuccessful (NG)
In the case of (1), although no ESD has occurred, it is determined that an error (NG) has occurred due to a read error, and the interval T1−interval T
ES when 2 <0 and read (R) is successful (OK)
Although D has not occurred, it is determined that an error (NG) has occurred due to a read error, and when interval T1−interval T2 <0 and read (R) is unsuccessful (NG), ESD occurs and a read error Therefore, it is determined that an error (NG) has occurred. E0 indicates the standard waveform amplitude of a normal GMR head, and E indicates the observed waveform amplitude of the GMR head.

Thus, the present algorithm 207 is
It is possible to determine a normal head (OK) where D is not generated, a read error (NG) where no ESD is generated, and an abnormal head in which the magnetization direction of the fixed layer is reversed by the ESD.

In this embodiment, the fixed layer magnetization reversal correction 208 is performed for the GMR head in which the fixed layer reversal 211 is determined.
To return to normal magnetization, or perform reproduction waveform inversion 209 to perform normal reproduction of data by waveform inversion although there is a GMR element determination, or perform sense current direction inversion 210 to initialize magnetization inversion of the fixed layer. This makes it possible to deal with abnormalities in the GMR head. When the fixed layer magnetization reversal correction 208 is performed, the reproduction waveform 202 is obtained again to confirm the correction, and the degree of the magnetization reversal correction of the GMR head can be adjusted by feedback.

In the above cases, even if the interval T1 is equal to or equal to the interval T2, the output having a low output is partially inverted, and the precursor of the GMR head abnormality is evaluated by combining the output with the output. be able to. For example, when there is no abnormality in the resistance value and the value is close to the interval T1−interval T2 = 0, the reproduction output is lost if the fixed layer faces the same lateral direction (track width direction) as the free layer during the inversion. T
Since 1-interval shows a value close to T2 = 0, it is possible to evaluate a precursor of abnormality.

In the magnetic head evaluation method according to the present invention, an asymmetric interval T1 and an interval T2 are written, the written interval T1 and the interval T2 are reproduced, and the interval and the reproduced waveform amplitude are shown in FIG. By incorporating the algorithm 207 and others into the magnetic disk device, the magnetic head manufacturing device, and the inspection device, it is possible to evaluate the abnormality of the GMR head in the actual device, the manufacturing process, and the evaluation process.

This magnetic disk drive comprises a normal magnetic head, a magnetic disk, a spindle motor (drive mechanism), an actuator and a control circuit. The control program of the control circuit incorporates the algorithm 207 shown in FIG. 2 and others. The magnetic head inspection apparatus has a configuration similar to that of the magnetic disk apparatus, and is capable of replacing a magnetic head to be evaluated or a magnetic head assembly equipped with the magnetic head.
The algorithm 207 shown in FIG.

More specifically, a magnetic head evaluation apparatus for evaluating a magnetic head equipped with a GMR element including a fixed layer according to the present invention includes a recording medium, a spindle motor for driving the recording medium to rotate, and A data recording / reproducing circuit for recording / reproducing data on / from a recording medium using a magnetic head for performing evaluation, and a control circuit for controlling the data recording / reproducing circuit, and evaluating a magnetic head equipped with a GMR element including a fixed layer. In the evaluation apparatus for a magnetic head to be performed, the data recording / reproducing circuit records a recording pattern having a different time interval from a positive pulse to a negative pulse and a time interval from a negative pulse to a positive pulse on a recording medium. The recording pattern is reproduced to obtain a reproduction waveform, and the control circuit is configured to control the time interval from the positive pulse to the negative pulse and the time interval from the negative pulse to the positive pulse of the reproduction waveform. Comparing the interval, the evaluated reversal of magnetization direction of the fixed layer of the GMR element by the difference between the two time intervals, a time interval from the positive pulse to negative pulse T1,
When a time interval from the negative pulse to the positive pulse is a time interval T2 shorter than the time interval T1, when the value obtained by subtracting the time interval T2 from the time interval T1 is negative, the magnetization direction of the fixed layer of the GMR element is changed. It is evaluated that it has been reversed.

Also, a magnetic disk drive according to the present invention includes a recording medium, a spindle motor for rotating the recording medium, and a magnetic head on which a GMR element including a fixed layer is mounted.
A data recording / reproducing circuit for recording / reproducing data on / from a recording medium by the magnetic head; and a control circuit for controlling the data recording / reproducing circuit, wherein the data recording / reproducing circuit comprises a time interval T1 from a positive pulse to a negative pulse and the time interval A recording pattern including a time interval T2 from a negative pulse shorter than T1 to a positive pulse is recorded on a recording medium, and the recording pattern is reproduced from the recording medium to obtain a reproduction waveform. When the value obtained by subtracting the time interval T2 from T1 is negative, it is determined that the magnetization direction of the fixed layer of the GMR element has been reversed.

The magnetic head evaluation apparatus and the magnetic disk drive are not limited to determining that the magnetization direction of the fixed layer of the GMR element has been reversed when the value obtained by subtracting the time interval T2 from the time interval T1 is negative. As described in the above embodiment, even when the interval T1 is equal to or equal to the interval T2, the reproduced waveform having a low amplitude has a partial inversion. A precursor to anomalies can also be evaluated. Further, in the above description, G
Although the MR head has been described as an example, the same effect can be applied to a GMR head other than the spin valve type GMR head, a tunnel effect type MR head, a super lattice type MR head, and the like.

As described above, the magnetic head evaluation method according to the present embodiment, the inspection apparatus and the magnetic disk drive having the magnetic head evaluation function are provided with a time interval from a positive pulse to a negative pulse and a time interval from a negative pulse to a positive pulse. A recording pattern having a different time interval is recorded on a recording medium, and a time interval from the positive pulse to the negative pulse and a time interval from the negative pulse to the positive pulse of a reproduction waveform obtained by reproducing the recording pattern from the recording medium. In comparison, the reversal of the magnetization direction of the fixed layer of the GMR element can be detected and evaluated based on the difference between the two time intervals.

In the above embodiment, as shown in FIG. 1, data is recorded using a recording current waveform in which the time interval T1 from the positive pulse to the negative pulse is longer than the time interval T2 from the negative pulse to the positive pulse. However, the present invention is not limited to this. The time interval is set to T2> T1, and (T1-T2) in the algorithm 207 in FIG. GM by reversing like
It may be configured to detect an abnormality of the R head. Further, in the above-described embodiment, the detection of the time interval is set as the peak time interval. However, the time interval can be obtained at any waveform position other than the peak.

The present invention can also be represented as the following embodiments. <Embodiment 1> At the time of signal recording, the recording medium has a recording function in which a time interval from a positive pulse to a negative pulse and a time interval from a negative pulse to a positive pulse are different. A polarity judgment function that measures the interval and the time interval from the negative pulse to the positive pulse, and asymmetry of the time interval. <Embodiment 2> At the time of signal recording, the recording medium has a recording function in which a time interval from a positive pulse to a negative pulse and a time interval from a negative pulse to a positive pulse are different. A magnetic head inspection apparatus having an interval and a time interval from a negative pulse to a positive pulse, and having a polarity determination function by asymmetry of the time interval. <Third Embodiment> At the time of signal recording, the recording medium has a recording function in which a time interval from a positive pulse to a negative pulse and a time interval from a negative pulse to a positive pulse are different. A magnetic recording apparatus having a function of measuring an interval and a time interval from a negative pulse to a positive pulse, and determining a polarity by asymmetry of the time interval.

[0038]

As described above, the magnetic head evaluation method, the inspection apparatus and the magnetic disk drive having the magnetic head evaluation function according to the present invention can provide a time interval from a positive pulse to a negative pulse and a positive pulse to a negative pulse. A recording pattern having a different time interval from a pulse to a recording medium is recorded on a recording medium, and a time interval from the positive pulse to the negative pulse and a time interval from the negative pulse to the positive pulse of a reproduced waveform obtained by reproducing the recording pattern from the recording medium. And GMR is calculated by the difference between the two time intervals.
The reversal of the magnetization direction of the fixed layer of the device can be evaluated. In particular, by using the magnetic head inspection apparatus having the function of the present invention, a highly reliable GM without magnetic abnormality
An R head can be provided. Further, the magnetic recording device (magnetic disk device) having the function of the present invention can improve reliability by mounting a highly reliable GMR head having no magnetic abnormality.

[Brief description of the drawings]

FIG. 1 is a diagram showing a relationship between a recording pattern and a reproduced waveform for explaining the principle of the present invention.

FIG. 2 is a diagram for explaining an algorithm of a magnetic head evaluation method according to the present invention.

FIG. 3 is a diagram illustrating a magnetic disk drive.

FIG. 4 is a diagram illustrating a magnetic head.

FIG. 5 is a diagram illustrating an MR head.

FIG. 6 is a diagram illustrating a GMR effect.

FIG. 7 is a diagram for explaining reversal of the magnetization direction of a fixed layer.

FIG. 8 is a diagram illustrating inversion of output polarity due to inversion of a fixed layer.

[Explanation of symbols]

1: recording medium, 2: magnetic head, 3: actuator
4: spring, 5: slider, 6: element, 7: inductive head for recording, 8: coil, 9: magnetic core, 10: recording magnetization on a recording medium, 11: MR film, 12: reproduction electrode,
13: external magnetic field, 14: free layer, 15: fixed layer, 16:
Antiferromagnetic film.

 ──────────────────────────────────────────────────の Continuing from the front page (72) Inventor Nobumasa Kushida 2880 Kozu, Odawara-shi, Kanagawa Prefecture Storage Systems Division, Hitachi, Ltd. In-house F term (reference) 5D034 BA05 BB12 BB14

Claims (5)

[Claims] 1. A method for evaluating a magnetic head having a head element including a fixed layer, wherein a recording pattern having a different time interval from a positive pulse to a negative pulse and a different time interval from a negative pulse to a positive pulse is recorded. The time interval from the positive pulse to the negative pulse and the time interval from the negative pulse to the positive pulse of the reproduction waveform obtained by recording the recording pattern on the medium and reproducing the recording pattern from the recording medium are compared with each other. A method for evaluating a magnetic head, comprising: evaluating a reversal of a magnetization direction of a fixed layer of a head element. 2. The time interval from the positive pulse to the negative pulse is T1, the time interval from the negative pulse to the positive pulse is a time interval T2 shorter than the time interval T1, and the time interval T2 is a time interval from the time interval T1. 2. The method according to claim 1, wherein when the subtracted value is negative, it is evaluated that the magnetization direction of the fixed layer of the head element has been reversed. 3. A recording medium, a spindle motor for rotationally driving the recording medium, a data recording / reproducing circuit for recording / reproducing data on / from the recording medium using a magnetic head for evaluation, and a control circuit for controlling these. In a magnetic head evaluation apparatus for evaluating a magnetic head equipped with a head element including a fixed layer, the data recording / reproducing circuit includes a time interval from a positive pulse to a negative pulse and a time interval from a negative pulse to a positive pulse. Recording a recording pattern having a time interval different from that of the recording medium, reproducing the recording pattern from the recording medium to obtain a reproduction waveform, and the control circuit controls a time interval from the positive pulse to the negative pulse of the reproduction waveform. And comparing the time interval from the negative pulse to the positive pulse, and evaluating the reversal of the magnetization direction of the fixed layer of the head element based on the difference between the two time intervals. Evaluation equipment 4. A recording pattern in which the data recording / reproducing circuit sets a time interval from the positive pulse to the negative pulse to T1, and a time interval from the negative pulse to the positive pulse to a time interval T2 shorter than the time interval T1. Is recorded on a recording medium, and the control circuit controls the time interval T1 to the time interval T1.
4. The magnetic head evaluation device according to claim 3, wherein when the value obtained by subtracting 2 is negative, it is evaluated that the magnetization direction of the fixed layer of the head element is reversed. 5. A recording medium, a spindle motor for rotating and driving the recording medium, a magnetic head on which a head element including a fixed layer is mounted, and data recording for recording and reproducing data on the recording medium by the magnetic head. In a magnetic disk drive including a reproducing circuit and a control circuit for controlling the same, the data recording / reproducing circuit is configured to control a time interval T1 from a positive pulse to a negative pulse and a time interval from a negative pulse to a positive pulse shorter than the time interval T1. A recording pattern including the interval T2 is recorded on a recording medium, and the recording pattern is reproduced from the recording medium to obtain a reproduced waveform. The control circuit determines that the value obtained by subtracting the time interval T2 from the time interval T1 is negative. In the magnetic disk drive, it is determined that the magnetization direction of the fixed layer of the head element has been reversed.