JP2001297403A - Method and device for improving property of thin film magnetic head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the novel method and device for improving the property of a thin film magnetic head capable of enhancing the property improvement so that the generation of pop-corn noise is surely eliminated or reduced. SOLUTION: The noise generated in the reading signal after the writing operation, is suppressed or reduced by impressing the external alternating magnetic field on the composite thin film magnetic head while making the writing current flow into an inductive write-in head element of the composite thin film magnetic head which is provided with the inductive write-in head element and an MR read-out head element.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for improving the noise characteristics of a composite thin film magnetic head having an inductive write head element and a magnetoresistive (MR) read head element.

[0002]

2. Description of the Related Art In recent years, as the areal recording density of a hard disk drive has been improved, the performance of a thin film magnetic head has been required to be improved. Therefore, instead of a thin-film magnetic head that performs both writing and reading with an inductive head element, writing is performed with an inductive head element and reading is performed with an MR head element stacked on the inductive head element. Composite thin film magnetic heads are widely used.

In this type of composite type thin-film magnetic head, when a read operation is performed after a write operation, a pulse-like noise (popcorn) having a peak value significantly higher than ordinary white noise is included in the read signal. Noise) is known to occur. The occurrence of the popcorn noise causes various problems such as causing an error in reading the read information.

In order to reduce such popcorn noise, measures have conventionally been taken in designing and manufacturing processes of the thin-film magnetic head, such as optimizing the shape and composition of the magnetic layer of the inductive write head element.

[0005]

However, it is extremely difficult to reliably reduce popcorn noise with the conventional measures as described above.

Also, for example, a thin-film magnetic head is mounted on a suspension, and signal lead lines and terminals are connected thereto.
After a product having a high added value is detected, all products having popcorn noise are discarded as defective products, so that there is a problem that the yield is low and the loss is large.

In the patent application (Japanese Patent Application No. 11-352538) prior to the present application, the present applicant improves the popcorn noise characteristic of a magnetic head by flowing a current larger than a normal write current to a write head element. Suggest a way. However, according to this method, the noise characteristics are improved by the heat generated by the current, so that the processing time is prolonged, and there is a possibility that the element may be deteriorated due to the flow of a current exceeding the specified value.

Accordingly, an object of the present invention is to provide a novel method and apparatus for improving the characteristics of a thin-film magnetic head capable of improving the characteristics so that popcorn noise is reliably eliminated or reduced.

Another object of the present invention is to provide a method and an apparatus for improving the characteristics of a thin-film magnetic head which can improve the characteristics in a short time and with good reproducibility.

It is still another object of the present invention to provide a method and an apparatus for improving the characteristics of a thin-film magnetic head which can easily improve the characteristics without applying a load to the head element.

[0011]

According to the present invention, there is provided a composite thin film magnetic head having an inductive write head element and an MR read head element. A method for improving the characteristics of a thin-film magnetic head is provided which suppresses or reduces noise generated in a read signal after a write operation by applying an external alternating magnetic field to the thin-film magnetic head.

The inventors of the present application have proposed that when an external alternating magnetic field is applied to a composite thin film magnetic head that generates popcorn noise while applying a write current to an inductive write head element, this popcorn It has been found that noise does not occur.
Therefore, even if the magnetic head has popcorn noise, the characteristics can be improved, so that it is not discarded as a defective product, and the yield is greatly improved. Moreover, since it is only necessary to apply a normal write current and apply an external magnetic field at the same time, the characteristic improvement processing is simple, unnecessary load is not applied to the head element, and the characteristic is improved in a short time and with good reproducibility. It can be performed.

Preferably, the external alternating magnetic field applied to the composite thin-film magnetic head is larger than the magnetic field normally applied from the magnetic medium to the composite thin-film magnetic head.

After applying a write current to the inductive write head element, it is determined whether or not popcorn noise is generated in a read signal from the MR readhead element, and it is determined that popcorn noise is generated. It is more preferable to perform the above-described noise characteristic improvement processing.

The noise characteristic improving process is performed on a plurality of composite thin film magnetic heads arranged on a head block.
For a composite thin film magnetic head separated into a single unit, for a composite thin film magnetic head mounted on a suspension, or for a plurality of composite thin film magnetic heads in a plurality of head suspension assemblies mounted on a head stack assembly Preferably, it is performed on the other hand.

According to the present invention, it is further possible to determine whether or not noise has occurred in a read signal after a write operation of a composite thin film magnetic head including an inductive write head element and an MR read head element. Means for applying a write current to the inductive write head element, means for applying an external alternating magnetic field to the composite thin-film magnetic head, and when the determination means determines that noise has occurred,
A characteristic improvement of a thin-film magnetic head comprising control means for suppressing or reducing the above-mentioned noise by applying an external alternating magnetic field from an external alternating magnetic field applying means in a state where a writing current is applied to the inductive type write head element from the conducting means. An apparatus is provided.

It is preferable that the means for applying the external alternating magnetic field is means for applying an external alternating magnetic field larger than the magnetic field normally applied to the composite thin-film magnetic head from the magnetic medium.

[0018]

FIG. 1 is a block diagram schematically showing a configuration of an apparatus for improving the characteristics of a thin-film magnetic head according to an embodiment of the present invention. This embodiment is applicable to a plurality of thin film magnetic heads aligned on a head block (bar).
This is a device that also attempts to improve popcorn noise characteristics when testing electrical characteristics with a ρ-H tester. Therefore, since many elements of a generally used ρ-H tester can be used, it is very easy to configure the device.

In FIG. 1, reference numeral 10 denotes a Helmholtz coil (air-core coil) for generating an external magnetic field applied to a composite thin film magnetic head including an inductive element as a write head element and an MR element as a read head element. In the present embodiment, they are installed such that their long axes are parallel to the vertical direction. The Helmholtz coil 10 is electrically connected to a Helmholtz coil excitation power supply 11, and its driving is controlled by an instruction given from a control computer 12. In the Helmholtz coil 10, a mounting table 13a of the XYZ-θ table 13 and a head block or bar 14 temporarily fixed on the mounting table 13a are provided.

The head block 14 forms a large number of composite thin-film magnetic heads on a wafer by thin-film technology,
The wafer is cut in rows to include a plurality of composite thin film magnetic heads, and the air bearing surface (A
BS) is polished to finish gap depth processing. Therefore, in the head block 14, a plurality of composite thin-film magnetic heads before being separated into a single unit exist in a row.

The first probe pin 15a is connected to the output terminal (61) of the MR element of each head in the head block 14.
a, see FIG. 6). The probe pins 15a and the respective output terminals are provided at a fixed position so as to be electrically contactable with each other, and control the XYZ-θ table 13 and drive the same. The alignment is performed by the XYZ-θ driver 16. The position of the first probe pin 15a and each output terminal is adjusted by capturing an image of this portion via the optical system 17.
It can be monitored by a CD imager 18 and a TV monitor 19 that displays this image.

The second probe pin 15b is connected to the input terminal (61b, FIG. 6) of the inductive head element of each head.
) Is provided at a fixed position so as to be electrically contactable with the probe pin 15b and each input terminal.
XYZ-θ table 13 and X for driving and controlling the same
The alignment is performed by the -YZ-θ driver 16.
This alignment part is also imaged via the optical system 17 C
It can be monitored by a CD imager 18 and a TV monitor 19 that displays this image. Actually, the first probe pin 15a and the second probe pin 15b are integrated and fixed, and the positioning of the XYZ-θ table 13 is performed at one time.

A head amplifier circuit 20 used in, for example, a disk drive is connected to the second probe pin 15b. An oscillator 21 is connected to the head amplifier circuit 20 so that the head amplifier circuit 20
From this point, a high-frequency write current can be supplied to the inductive head element of the magnetic head via the second probe pin 15b. This write current is
This is a rectangular wave in a frequency band (1 MHz to 200 MHz) usually used for writing in a magnetic head.

The first probe pin 15a is connected to a head amplifier circuit 20 which supplies a sense current to the MR type head element and receives an output voltage from the MR type head element. A constant current source 22 for current is connected.

The head amplifier circuit 20 is connected to a noise detection circuit 23 for repeatedly performing a predetermined number of write and read operations to detect the number of occurrences of noise. The noise detection circuit 23 receives an output from the noise detection circuit 23. A control computer 12 for determining whether or not popcorn noise has occurred, and further performing characteristic improvement processing, is connected.

The head amplifier circuit 20, Helmholtz coil power supply 11 and XYZ-θ driver 16 are also connected to the control computer 12, and perform predetermined control operations according to instructions from the computer.

FIG. 2 is a block diagram schematically showing a configuration example of the noise detection circuit 23.

In FIG. 2, reference numeral 231 denotes a high-pass filter for extracting only high-frequency components from the output voltage of the MR read head element output from the head amplifier circuit 20. One input terminal of two comparators 232 and 233 is connected to the output side of the high-pass filter 231. An upper threshold voltage V _TH for identifying popcorn noise is applied to the other input terminal of the comparator 232, and a lower threshold voltage for identifying popcorn noise is applied to the other input terminal of the comparator 233. The voltage _VTL is applied. The outputs of the comparators 232 and 233 are connected to one input terminal of an AND circuit 235 via a pulse generation circuit 234 such as a monostable multivibrator.

The other input terminal of the AND circuit 235 has
Read gate signal R from timing signal generation circuit 237
G is configured to be applied. AND circuit 23
5 is connected to the input terminal of the noise counter 236. The noise counter 236 is configured to receive a timing signal from the timing signal generation circuit 237. The noise counter 236 further includes
The count value is output to the control computer 12.

The timing signal generation circuit 237 is configured to output a read gate signal RG and a timing signal based on a change in the count value of the noise detection cycle counter 238.

FIG. 3 is a flowchart showing a control program of the computer 12, and a method for improving the characteristics of the thin-film magnetic head according to the present invention will be described below with reference to FIG.

First, the position between the output terminal of the MR element of the target magnetic head and the first probe pin 15a on the head block 14 fixed on the mounting table 13a of the XYZ-θ table 13 The alignment and the alignment between the input terminal of the write element of the magnetic head and the second probe pin 15b are performed (step S1). For this alignment, a well-known alignment technique of moving the XYZ-θ table 13 by instructing the XYZ-θ driver 16 is used.

Next, the frequency of occurrence of popcorn noise is detected (step S2).

FIG. 4 is a flowchart for explaining an example of the detection processing in step S2 in detail.

First, the noise detection cycle counter 238
Is set to the number of noise detection cycles, and the noise counter 236 is reset to an initial value (step S2).
1). The number of noise detection cycles is determined as appropriate. For example, it may be 100, 500, 5000, or any other constant value.

Next, a write operation is performed by controlling the head amplifier circuit 20 (step S22).
This write operation is performed by applying a rectangular wave write current of a preset frequency and amplitude to the inductive write head element of the magnetic head for, for example, several tens to several hundreds of seconds. The frequency of the write current is set in the frequency band (1 MHz to 200 MHz) normally used for writing.
z).

Next, it is delayed by a predetermined period D (step S23). This delay time is, for example, several μsec. The delay period D is provided for performing the read operation after the transient response of the head amplifier circuit 20 at the time of shifting from the write operation to the read operation.

Next, a read operation is performed by controlling the head amplifier circuit 20 (step S24).
In this read operation, a sense current is applied to the MR type read head element of the magnetic head, and the read gate signal R is output from the timing signal generation circuit 237 of the noise detection circuit 23.
G is applied to the head amplifier circuit 20 and the AND circuit 235. The period of the read operation is, for example, several tens of microseconds.

Next, the read signal RS output from the head amplifier circuit 20 is applied to the comparators 232 and 233 via the high-pass filter 231 of the noise detection circuit 23, and is compared with the threshold voltage V _TH and the threshold voltage V _TL. ,
It is determined whether it is within the set range (step S25).

When the read signal RS is not within the set range,
The trigger signal is output from the AND circuit 235 and applied to the noise counter 236.
36 increments the contents by +1 (step S2
6). When the read signal RS is within the set range, no trigger signal is output from the AND circuit 235, and the content of the noise counter 236 does not change.

Next, the content of the noise detection cycle counter 238 is incremented by -1 according to the timing signal output from the timing signal generation circuit 237 (step S27).

Thereafter, the noise detection cycle counter 23
It is determined whether the content of No. 8 has become zero (step S28). If the count becomes zero, the popcorn noise occurrence frequency detection processing is terminated, and step S3 in FIG.
Proceed to. If it is not zero, the process returns to step S22, and the above-described series of processes from the write operation is repeated.

FIG. 5 is a waveform diagram for explaining the relationship among a read signal, a threshold voltage, a trigger signal, a read gate signal RG, and the like of the composite type thin-film magnetic head in one write operation and one read operation.

In the figure, W is a write operation period, D is a delay period after the write operation, R is a read operation period, RG is a read gate signal which is at a high level only during the read operation period, and RS is an MR type read head element. Read signal,
V _TH indicates an upper threshold voltage, V _TL indicates a lower threshold voltage, and TG indicates a count trigger signal of a noise counter.

When a read operation is performed after a write operation, there is a magnetic head that generates pulse-like popcorn noise PN having a peak value considerably higher than that of normal white noise in the voltage waveform of the read signal RS. Such a popcorn noise PN has a threshold voltage V as shown in FIG.
_{Since TH} or V _TL is exceeded, the output of the comparator 232 or 233 is inverted, and the trigger signal T
G is output and the noise counter 236 advances.

Therefore, according to the detection processing of FIG. 4, the frequency of occurrence of popcorn noise, which indicates how many times popcorn noise has occurred in a predetermined number of noise detection cycles, can be obtained.

After the detection processing is completed, it is determined whether or not the frequency of occurrence of the detected popcorn noise (number of occurrences / number of noise detection cycles) exceeds an allowable value (step S3).

If the frequency of occurrence does not exceed the allowable value, the magnetic head is determined to be non-defective with respect to popcorn noise (step S4), and the characteristic improvement processing is not performed.

If the frequency of occurrence exceeds the allowable value, the characteristic improvement processing is performed by simultaneously applying a write current and an external alternating magnetic field to the magnetic head (step S).
5). Specifically, by controlling the head amplifier circuit 20, a rectangular wave write current having a preset frequency and amplitude is applied to the inductive write head element of the magnetic head, and the excitation power supply 11 is further controlled. This is performed by simultaneously applying an external alternating magnetic field to the head block 14.

The frequency of the write current is a frequency band (1 MHz to 200 MHz) used for normal writing, and the intensity is a current value used for normal writing.

The strength of the external alternating magnetic field is set to a value larger than the magnetic field normally applied from the magnetic medium to the magnetic head. The frequency of the external alternating magnetic field is not particularly limited, and may be a low frequency to a microwave band. Even in the case of DC, if the polarity is changed and applied multiple times, it becomes an external alternating magnetic field. For example, in this embodiment, 1 kHz is used.

As is well known, the Helmholtz coil 10
Generates a magnetic field having a strength proportional to the applied current in the direction of its major axis, so that the magnitude and frequency of the drive current may be indicated to the excitation power supply 11.

FIG. 6 also illustrates the external alternating magnetic field applied to the head block 14. In this embodiment, the direction of the external magnetic field is the same as the direction of the magnetic field applied when the magnetic head is actually running on the magnetic medium, that is, the direction perpendicular to the ABS 14a of the head block 14. However, the same result can be expected in any other direction as the external alternating magnetic field. In the present embodiment, the waveform of the external magnetic field is an AC waveform that changes in a positive or negative sine wave shape as indicated by 60 in FIG.

In FIG. 6, reference numeral 61a denotes an output terminal of the MR element, 61b denotes an input terminal of the write element, and the first probe pin 15a is connected to the output terminal 61a of the MR element of the magnetic head to be inspected. This shows a state in which the second probe pins 15b are in contact with the input terminals 61b of the write element, respectively.

Next, the same noise detection processing as in step S2 is performed (step S6).

Thereafter, it is determined whether or not the frequency of occurrence of the detected popcorn noise exceeds an allowable value as in step S3 (step S7).

If the frequency of occurrence does not exceed the allowable value, it is determined that the magnetic head is non-defective with respect to popcorn noise as a result of the improvement of the characteristics (step S).
4).

If the occurrence frequency exceeds the allowable value, the magnetic head is determined to be defective, and all the processing for the magnetic head is completed (step S8).

As described above, according to the present embodiment,
It is determined whether or not popcorn noise occurs at an allowable frequency for the magnetic head, and if so, the characteristic improvement processing is performed by simultaneously applying a write current and an external alternating magnetic field. In the following, the improvement of characteristics in which popcorn noise does not occur by simultaneously applying the write current and the external alternating magnetic field will be described. This will be described with reference to FIG.

FIGS. 7A and 7B are waveform diagrams respectively showing read signals of a magnetic head sample having no popcorn noise and a magnetic head sample having popcorn noise.

In the drawing, reference numerals 71 and 72 denote the highest value and the lowest value of the read signal at each time when the cycle of the write operation and the read operation is repeated 5000 times,
Reference numeral 73 denotes a value of the read signal at each time in the last cycle, and RG denotes a read gate signal. It can be seen that the sample in which popcorn noise is present is considerably distorted in the maximum value and the minimum value 71 and 72 during the read period in which the read gate signal RG is at the high level, as compared with the sample not having popcorn noise.

FIG. 8 shows that, for a sample in which popcorn noise is present, the external alternating magnetic field was set to 1600 A / m (20
FIG. 14 is a diagram illustrating a part of a count value of a noise counter and a read signal waveform when noise detection is performed while increasing the noise by Oe). However, each signal waveform is the same as in FIG. 5,000 cycles of write and read operations, write current 40 mA _0-P and 50M
Hz, and the delay period D is 3.0 μsec.

The count operation changes during noise detection by applying an external alternating magnetic field of 38,400 A / m shown in FIG. 8 (E).
As shown in (F), the occurrence of popcorn noise was drastically reduced.

FIG. 9 shows an external alternating magnetic field of 4000 A / m for a separate sample in which popcorn noise is present.
It is a figure which shows the count value of a noise counter, and a read-out signal waveform when noise detection is performed in increments of (50 Oe) and application of an external alternating magnetic field is stopped halfway. Each signal waveform is the same as that in FIG. 7, the write operation and the read operation have 5,000 cycles, and the write current is 40 mA.
_0-P and 50 MHz, and the delay period D is 3.0 μsec.

As shown in FIG. 9C, 20,000 A / m
After the external alternating magnetic field of (250 Oe) was applied and noise was detected, as shown in FIG. 9 (D), the application of the external alternating magnetic field was stopped and noise detection was performed. I have. This was the same even when an external alternating magnetic field of 20000 A / m (250 Oe) was applied again, as shown in FIG.

FIG. 10 shows the presence of popcorn noise.
External alternating magnetic field is applied to the sample by increasing it sequentially
Of foreign exchange of 40000A / m (500Oe)
Noise when noise is detected by applying a magnetic field
FIG. 7 is a diagram showing a count value of a read counter and a read signal waveform.
is there. However, the signal waveforms are the same as in FIG.
You. The cycle of the write operation and the read operation is 5000
Times, write current is 40mA _0-PAnd 50MHz, delay
The period D is 3.0 μsec.

When noise detection is performed by applying an external alternating magnetic field of 40000 A / m shown in FIG. 10B, the occurrence of popcorn noise is drastically reduced. This is shown in FIG.
As shown in the above, the same was true even when the application of the external alternating magnetic field was stopped. Therefore, it has been proved that by applying an external alternating magnetic field having a certain strength or more in a state in which the write current is applied, it is possible to improve the characteristic that the generation of popcorn noise is drastically reduced.

As described above, according to the present embodiment, it is possible to improve characteristics so that popcorn noise does not occur by applying a somewhat strong external alternating magnetic field while supplying a write current to the inductive write head element. it can. As described above, even with a magnetic head having popcorn noise, the characteristics can be improved, so that it is not discarded as a defective product, and the yield is greatly improved. Moreover, since it is only necessary to apply a normal write current and apply an external magnetic field at the same time, the characteristic improvement processing is simple, unnecessary load is not applied to the head element, and the characteristic is improved in a short time and with good reproducibility. It can be performed.

In general, in order to manufacture a composite type thin film magnetic head and incorporate it into a magnetic disk drive, the steps schematically shown in FIG. 11 are taken. That is, first, a large number of thin film magnetic heads are formed in a matrix on the wafer (step S111). Next, the wafer is cut to form a head block or bar in which a plurality of thin film magnetic heads are arranged in a row (step S112). Next, the head block is cut to obtain a thin film magnetic head separated into single pieces (step S113). Thereafter, the thin-film magnetic head is mounted on a suspension to obtain a head suspension assembly (step S114). Then
A plurality of head suspension assemblies are mounted on a carriage to obtain a head stack assembly (Step S)
115). Thereafter, the head stack assembly is mounted on the magnetic disk drive (Step S116).

In the above embodiment, step S112
After that, that is, at the time shown in the figure, processing for improving the characteristics of the thin-film magnetic head is performed. However, the characteristic improvement processing of the present invention is performed after completion of the wafer process (see FIG. 4), after separation into the magnetic head alone (see FIG. 4), after mounting on the suspension (see FIG. 5), and after forming the head stack assembly. It is obvious that the process may be performed (see FIG. 3) or after mounting on the magnetic disk drive (see FIG. 5).

The embodiments described above are merely examples of the present invention, and do not limit the present invention. The present invention can be embodied in other various modifications and alterations. Therefore, the scope of the present invention is defined only by the appended claims and their equivalents.

[0072]

As described in detail above, in the present invention,
The characteristics of a composite thin-film magnetic head that generates popcorn noise are improved by applying an external alternating magnetic field while supplying a write current to an inductive write head element. Therefore, even if the magnetic head has popcorn noise, the characteristics can be improved, so that it is not discarded as a defective product, and the yield is greatly improved. Moreover, since it is only necessary to apply a normal write current and apply an external magnetic field at the same time, the characteristic improvement processing is simple, unnecessary load is not applied to the head element, and the characteristic is improved in a short time and with good reproducibility. It can be performed.

[Brief description of the drawings]

FIG. 1 is a block diagram schematically showing a circuit configuration of an apparatus for improving characteristics of a composite magnetic head according to an embodiment of the present invention.

FIG. 2 is a block diagram schematically illustrating a configuration example of a noise detection circuit in the embodiment of FIG. 1;

FIG. 3 is a flowchart showing a control program of a computer in the embodiment of FIG.

FIG. 4 is a flowchart showing details of a popcorn noise occurrence frequency detection process in FIG. 3;

FIG. 5 is a waveform diagram for explaining the relationship among a read signal, a threshold voltage, a trigger signal, a read gate signal RG, and the like of the composite thin-film magnetic head in one write operation and one read operation in the embodiment of FIG. 1; .

FIG. 6 is a diagram showing a relationship between a probe pin and an electrode of a magnetic head and explaining an external alternating magnetic field applied to a head block in the embodiment of FIG. 1;

FIG. 7 is a waveform diagram showing read signals of a magnetic head sample having no popcorn noise and a magnetic head sample having popcorn noise.

FIG. 8 is a diagram showing a part of a count value of a noise counter and a read signal waveform when noise is detected by increasing an external alternating magnetic field for a sample having popcorn noise.

FIG. 9 is a diagram showing a count value of a noise counter and a read signal waveform when noise is detected by changing an external alternating magnetic field for a sample having popcorn noise.

FIG. 10 is a diagram illustrating a count value of a noise counter and a read signal waveform when noise is detected by changing an external alternating magnetic field for a sample having popcorn noise.

FIG. 11 is a process diagram schematically showing a process of manufacturing a composite thin-film magnetic head and incorporating it into a magnetic disk drive.

[Explanation of symbols]

 Reference Signs List 10 Helmholtz coil 11 Helmholtz coil excitation power supply 12 Control computer 13 XYZ-θ table 13a Mounting table 14 Head block or bar 14a Air bearing surface (ABS) 15a First probe pin 15b Second probe pin 16 XYZ-θ driver 17 Optical system 18 CCD imager 19 TV monitor 20 Head amplifier circuit 21 Oscillator 22 Constant current source 23 Noise detection circuit 60 External alternating magnetic field 61 a Output terminal 61 b Input terminal 231 High-pass filter 232, 233 Comparator 234 Pulse generation circuit 235 AND circuit 236 Noise counter 237 Timing signal generation circuit 238 Noise detection cycle counter

Claims (9)

[Claims] 1. A composite thin film magnetic head having an inductive write head element and a magnetoresistive read head element, wherein an external alternating magnetic field is applied to the composite thin film magnetic head while applying a write current to the inductive write head element. , By suppressing or reducing noise generated in a read signal after a write operation. 2. The method according to claim 1, wherein the external alternating magnetic field applied to the composite thin-film magnetic head is larger than the magnetic field normally applied from the magnetic medium to the composite thin-film magnetic head. . 3. After a write current is applied to the inductive write head element, it is determined whether or not the noise is generated in a read signal from the magnetoresistive read head element. 3. The method according to claim 1, wherein when it is determined that the noise is present, the noise characteristic improvement processing is performed. 4. 4. The method according to claim 1, wherein the noise characteristic improving process is performed on a plurality of composite thin-film magnetic heads arranged on a head block. Method. 5. The method according to claim 1, wherein the noise characteristic improving process is performed on a composite type thin-film magnetic head separated into a single unit. 6. The method according to claim 1, wherein the noise characteristic improving processing is performed on a composite thin-film magnetic head mounted on a suspension. 7. The method according to claim 1, wherein the noise characteristic improving processing is performed on a plurality of composite thin-film magnetic heads in a plurality of head suspension assemblies mounted on the head stack assembly. Or the method of claim 1. 8. A means for judging whether or not noise has occurred in a read signal after a write operation of a composite thin-film magnetic head including an inductive write head element and a magnetoresistive read head element, and said inductive means. Means for applying a write current to the type write head element, means for applying an external alternating magnetic field to the composite thin-film magnetic head, and when the determination means determines that the noise is generated, Control means for suppressing or reducing the noise by applying an external alternating magnetic field from the external alternating magnetic field applying means in a state where a write current is applied to the type write head element. Improvement device. 9. The apparatus according to claim 8, wherein said means for applying an external alternating magnetic field is means for applying an external alternating magnetic field larger than a magnetic field normally applied to said composite thin-film magnetic head from a magnetic medium. The described device.