JP2003248911A - Measuring apparatus of magnetic head and measuring method used in the apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize a direct and high-resolution observation of a magnetic saturation field that is a magnetic field characteristic of a recording head so that measuring performance of the recording head can be improved. <P>SOLUTION: In a measuring method used in a measuring apparatus of a magnetic head that performs measurement on at least one measuring point on a recording head 3, a combined current of a direct current and an alternating current is applied to the recording head 3. Consequently, a magnetic field is generated from that recording head 3, and a probe 10 is approached to the recording head 3 in a condition where a cantilever 2 supporting the probe 10 for scanning the measuring point is controlled to be excited in a predetermined frequency and amplitude. Thus, a signal corresponding to dynamic interaction exerted on the probe 10 by the magnetic field generated from the recording head 3 according to the applied current is detected as an oscillation frequency change of the cantilever 2. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention generally relates to a magnetic head measuring apparatus using a magnetic force microscope (MFM), and more particularly to a magnetic head measuring apparatus for measuring a magnetic field characteristic of a recording head.

[0002]

2. Description of the Related Art Conventionally, in a manufacturing process of a magnetic head used for a hard disk drive, for example, a measuring process for measuring magnetic field characteristics such as a magnetic field distribution of a recording head (write head) included in the magnetic head and a saturation phenomenon of the magnetic field. Is essential. The recording head is, for example, an inductive thin film head, and has a magnetic gap that generates a recording magnetic field according to the signal current applied to the coil.

As a measuring method in the measuring process, there are (1) a method using a measuring device dedicated to a head disk called a spin stand, and (2) a dedicated magnetic head measuring device utilizing a magnetic force microscope (MFM). The method to use,
(3) A method based on computer simulation is known.

In the measurement method using the spin stand,
The measurement signal is recorded on the disk recording medium while changing the write current value for the recording head to be measured, and the recording signal is reproduced by the reproducing head (read head). Then, the spin stand measures the magnetic field characteristics of the recording head to be measured using the recording signal output from the reproducing head.

Further, in the measuring method using the MFM, a DC (direct current) current is applied to the recording head to be measured to generate a DC magnetic field (recording magnetic field) generated from the recording head.
Is measured by MFM.

In the computer simulation method, a DC magnetic field (recording magnetic field) generated from a recording head to be measured when a DC (direct current) current is applied to the recording head is measured by computer simulation.

[0007]

The various conventional measuring methods described above have the following problems.

First, in the measuring method using the spin stand, since the recording signal is measured through the disk recording medium and the reproducing (MR) head, the measurement result including these characteristics can be obtained. become. Therefore, the saturation magnetic field of the recording head cannot be directly observed.
Further, it is estimated that the saturation phenomenon occurs from the angle (edge) of the magnetic poles forming the recording head. However, this measurement method cannot capture the phenomenon locally.

Further, in the measurement method using MFM, D
Since only the C current is applied to measure the saturation magnetic field, improvement in resolution cannot be expected. When the DC current value is increased, a very large magnetic field is generated from the recording head. For this reason,
The interaction between the probe used in the MFM and the recording magnetic field from the recording head extends not only to the tip of the probe but also to the back of the probe. Further, since the interaction on the back surface of the probe also includes the magnetic field from the periphery of the probe, the interaction effect on the back surface of the probe becomes very large.
Therefore, the contribution from the tip of the probe is relatively reduced, and the resolution is lowered.

Further, the computer simulation cannot measure the actual magnetic field distribution of the recording head.

The present invention has been made in view of the above circumstances, and it is possible to directly observe the saturation magnetic field, which is the magnetic field characteristic of the recording head, with high resolution, and as a result, it is possible to improve the measurement performance of the recording head. An object is to provide a magnetic head measuring device.

[0012]

A magnetic head measuring device according to the present invention is a magnetic head measuring device for measuring at least one measuring point on a recording head, and has a magnetic substance in at least a part thereof. Then, a probe for scanning the measurement point, a cantilever supporting the probe, a vibrating means for vibrating the cantilever, and a displacement of the cantilever vibrated by the vibrating means are detected. Displacement detecting means, based on the detection result of the displacement detecting means, the vibrating means controls the vibrating means to vibrate the cantilever at a predetermined frequency and amplitude, a direct current to the recording head, and Apply a current that is a combination of alternating currents,
Current applying means for generating a magnetic field from the recording head,
A signal detection unit that detects a signal corresponding to a mechanical interaction exerted on the probe by a magnetic field generated from the recording head according to a current applied by the current application unit, as a vibration frequency change of the cantilever. It is characterized by having.

The measuring method according to the present invention is a measuring method applied to a magnetic head measuring device for measuring at least one measuring point on a recording head, and a direct current is applied to the recording head. And a state in which a cantilever supporting a probe for scanning the measurement point is excited by a predetermined frequency and amplitude by applying a current including an alternating current and generating a magnetic field from the recording head. In this case, the probe is brought close to the recording head, and a signal corresponding to a mechanical interaction exerted on the probe by a magnetic field generated from the recording head in response to the current application is detected as a vibration frequency change of the cantilever. It is characterized by doing.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. (Structure of Magnetic Head Measuring Device) As shown in FIG. 1, the measuring device of this embodiment is roughly classified into a measuring device main body 1 and a computer 20. The measuring device body 1 is a dedicated device for measuring the magnetic field characteristics of a recording head (hereinafter also referred to as a sample) 3 using a magnetic force microscope (MFM). Here, the MFM is a kind of scanning probe microscope, and is usually a cantilever (leaf spring member).
The probe mounted on the is brought close to the sample to be measured, and the magnetic field generated from the sample in a non-contact state is detected by utilizing the magnetic force interaction (force or force gradient).

The measuring apparatus main body 1 includes a cantilever 2 which supports a magnetic (or magnetically coated) probe 10, and a vibrating piezoelectric element 5 for applying a vibration of a constant vibration amplitude to the cantilever 2. Have. The vibration piezoelectric element 5 vibrates the cantilever 2 at a mechanical resonance frequency (ωr) of the cantilever 2 or a frequency in the vicinity thereof and at a predetermined amplitude in accordance with a control signal from an AGC circuit 23 described later. .

On the other hand, sample 3 which is the recording head to be measured
Are held by the scanning piezoelectric element 4 which is driven and controlled in the three-dimensional directions of the X axis, the Y axis, and the Z axis. The scanning piezoelectric element 4 has a function of changing the three-dimensional relative position and relative distance between the sample 3 and the probe 10 in response to a control signal from a feedback circuit 12 described later.

Further, the measuring device main body 1 includes a displacement detector 7
, Phase shifter 22, and AGC (Automatic Gain Control)
It has a circuit 23, a frequency demodulator 21, a synchronous detector 9, and an amplitude / DC voltage converter 11.

In this embodiment, the frequency detection method using the frequency demodulator 21 is adopted as the method for detecting the mechanical interaction. Along with this, the displacement detector 7, the phase shifter 22, the AGC circuit (automatic gain control circuit) 23, and the oscillating piezoelectric element 5 constitute a positive feedback oscillation system to keep the displacement of the cantilever 2 constant during measurement. I am trying. In particular,
The phase shifter 22 and the AGC circuit 23 control the vibrating piezoelectric element 5 to vibrate the cantilever 2 at a predetermined frequency and amplitude based on the detection result of the displacement detector 7.

The displacement detector 7 detects the displacement of the cantilever 2.

The phase shifter 22 outputs a signal whose phase is shifted by a predetermined angle with respect to the phase of the signal output from the displacement detector 7. That is, the phase shifter 22 outputs a signal in which the phase of vibration of the cantilever 2 is changed. This phase shifter 22
The output signal of the displacement detector 7 and the AG
The phase difference from the output signal of the C circuit 23 can be kept constant. The AGC circuit 23 and the phase shifter 2
Even if the arrangement order of 2 is exchanged, there is no problem in measurement.

The AGC circuit 23 receives the output signal of the phase shifter 22 and controls its own output signal so that the amplitude of the vibration of the cantilever 2 or the amplitude of the signal to the oscillating piezoelectric element 5 becomes constant (automatic). Gain control).

The frequency demodulator 21 detects the resonance frequency change (frequency shift) of the cantilever 2 due to the interaction at the probe 10, based on the output signal of the displacement detector 7.

The synchronous detector 9 measures an AC (alternating current) component from the signal output from the frequency demodulator 21. That is,
The synchronous detector 9 extracts an amplitude component (corresponding to a magnetic field-current differential image) synchronized with the alternating current corresponding to the magnetic field of the recording head 3 detected by the mechanical interaction of the probe 10, and outputs it as a measurement signal. It is output to the computer 20 as 100.

The amplitude / DC voltage converter 11 converts the amplitude value of the AC signal from the output signal of the displacement detector 7 into a DC (DC) signal 102 and outputs it to the feedback circuit 12.
The feedback circuit 12 includes an amplitude / DC voltage converter 11
A drive control signal 103 for driving the scanning piezoelectric element 4 is output so that the amplitude of the output signal 102 from the device is kept constant (the probe-sample distance is kept constant), and
The signal is output to the computer 20 as a measurement signal 101 of the surface shape (concavo-convex image) of the sample 3.

The signal generator 13 is a circuit having a current source for supplying the signal current 104 for measurement to the coil of the recording head which is the sample 3. The signal current 104 is a combination of DC and AC, and is a signal current including the AC current (angular vibration frequency ωm) having a very small amplitude.
Further, the frequency of the AC current needs to be set lower than the vibration frequency of the vibration piezoelectric element 5. It is also possible to observe the saturation phenomenon of the high frequency magnetic field on the computer 20 side by setting the AC current as an amplitude modulation current amplitude-modulated with a predetermined carrier frequency and a modulation frequency.

The computer 20 performs overall control of the measuring apparatus main body 1 and also corresponds to the measurement signal 100 corresponding to the magnetic field-current differential image measured by the measuring apparatus main body 1 and the surface shape (concavo-convex image) of the sample. It has a function of performing signal processing on each of the measurement signals 101 to perform measurement evaluation.
Further, the computer 20 executes setting of all measurement conditions and acquisition of operating states of the apparatus body 1. Specifically, the computer 20 sets the time constant of the feedback circuit 12 and the scanning range of the scanning piezoelectric element 4. In addition, the frequency for generating the signal current from the signal generators 6 and 13,
Set operating conditions such as amplitude and offset.

The above-mentioned probe 10, cantilever 2, vibrating piezoelectric element 5, displacement detector 7, phase shifter 22, AGC circuit 23, frequency demodulator 21, synchronous detector 9, amplitude / DC voltage converter 11 The feedback circuit 12 and the scanning piezoelectric element 4 can be newly developed to perform the main measurement, but a commercially available or existing atomic force microscope (At
Omic Force Microscope (AFM) / MFM device.

The above-mentioned scanning piezoelectric element 4 is assumed to be fixed to the recording head 3, but the relative position between the probe 10 and the recording head 3 can be changed. Other arrangement configurations may be used as long as they are present.

In the frequency demodulator 21 described above, in addition to a simple detection method using an LC resonance circuit and a diode, a peak differential (peak differenti
al) detection, ratio detection, foster seal (Foster
Seeley) detection, PLL (phase locked loop) demodulation, SSB
(single sideband) demodulation, DSP (digital signal process)
A detection method such as digital demodulation using ssor) may be adopted.

Further, in the above-mentioned AGC circuit 23, a structure using a peak detector may be adopted in addition to a structure using a gain amplifier.

Further, in the phase shifter 22 described above, in addition to the configuration using an all-pass filter using an operational amplifier, a configuration using a triangular wave converter (for example, an integrating circuit) and a comparator, and a configuration using a PLL circuit are adopted. You may.

(Characteristics of Frequency Detection Method) In this embodiment, the frequency detection method is applied to the magnetic field saturation measurement of the recording head. At that time, the cantilever vibration is feedback-controlled by the positive feedback oscillation system and the phase is changed by the phase shifter (Applied Physics A 66, S885-S889 (199
8)), the Q value of the cantilever 2 can be effectively improved, and the magnetic field saturation phenomenon can be captured stably and with high sensitivity.
Further, in vacuum, the sensitivity can be further improved and the resolution can be increased.

In contrast to such a frequency detection method, a measuring device that employs a phase detection method using a phase detector has been proposed (Japanese Patent Application No. 2001-28551).
In the phase detection method, the resonance frequency ωr of the cantilever is measured in advance, and the frequency of the excitation signal is set to ωr in the signal generator that generates the excitation signal for exciting the cantilever.
Then, the cantilever is vibrated. The reason for setting the frequency of the excitation signal to ωr is that the phase change at this frequency is the steepest, and therefore the measurement can be performed in the most sensitive state. Resonance frequency ωr performed in advance
Is measured when the probe and the surface of the measurement sample (recording head) are sufficiently separated.

However, the resonance frequency ωr of the cantilever is closer to the sample (100 nm) as the probe approaches the sample.
From the following), the phase shift begins to change at the time of measurement due to the electrostatic force or magnetic force interaction due to the contact potential difference between the probe and the sample, which is different from the value when the probe is sufficiently separated from the sample. Such a deviation of the value becomes particularly remarkable in the range of several nm to 10 nm during the measurement. As a result, the detection sensitivity may decrease. Especially when the Q value of the cantilever is high, for example, when measuring in a vacuum or when a Q value control circuit is incorporated,
Such effects are likely to occur.

On the other hand, the frequency detection method (TR Albr
echt, P. Grutter, D. Horne, andD. Rugar, Journal o
f Applied Physics, Vol.69, p.668 (1991)), by controlling the vibration of the cantilever with a positive feedback oscillation system, even if the resonance frequency ωr changes,
It becomes possible to continue appropriately exciting the cantilever at the changed frequency.

Regarding such a frequency detection method, it has been reported that atomic level resolution is realized (for example, F.
J. Giessibl, Science 260, 67 (1995)), it is very effective to apply this method to the magnetic field saturation measurement of the recording head.

By applying this method to a high frequency characteristic measuring device (Japanese Patent Application No. 2001-85820), it is possible to observe the saturation phenomenon of the high frequency magnetic field.

(Measurement Procedure) The measurement procedure of this embodiment will be described below with reference to the flowchart of FIG.

Before the measurement, the phase shifter 22 is adjusted,
The phase difference between the output signal of the displacement detector 7 and the output signal of the AGC circuit 23 is set to π / 2 so that the Q value of the cantilever 2 is maximized. When this adjustment is possible, the amplitude of the output signal of the AGC circuit 23 takes the minimum value.

After the preparation for measurement is completed, the signal current 104 is applied from the signal generator 13 to the coil of the recording head which is the sample 3 (step S1). This signal current 10
4 is the sum of DC and AC (angular vibration frequency ωm). At this time, the amplitude of the AC current is set to a very small value.

Here, the smaller the amplitude of the AC current, the more the signal corresponding to the differentiation of the magnetic field can be obtained. However, considering the detection sensitivity of MFM, some amplitude is required. Considering that the maximum value of the signal amplitude in the actual recording head is 30 mA to 40 mA, it is ideal that the amplitude of the AC current is about 3 mA or less.

However, if the current is made too small, the measured AC component F _AC of the interaction becomes smaller than the noise of the measurement system, and the predetermined measurement becomes difficult. Therefore, it is necessary to set the current value so that a large signal can be obtained with respect to the noise level. When the noise of the circuit is reduced among the noise of the normal measurement system, the thermal noise of the cantilever 2 becomes dominant. This noise is thermostatistically fixed and cannot be removed. Therefore, it is necessary to perform the measurement while satisfying the following conditions.

[0043]

[Equation 1]

Here, A, Q, k, and ωr are the vibration amplitude of the cantilever, the Q value, the spring constant, and the resonance frequency, respectively. K _B and T are the Boltzmann constant and temperature, respectively, and B is the bandwidth of the measurement system. In the measurement of this embodiment, the bandwidth of the low-pass filter of the synchronous detector 9 is considered. The actual size of F _AC depends on the shape of the probe and the material of the magnetic material.
Depends on sputtering conditions and film thickness.

On the other hand, the frequency (ωm) of the AC current contained in the signal current 104 is the resonance frequency (ω) of the cantilever 2.
It should be 1/10 or less of r). The frequency (ωm) is the modulation frequency of the amplitude modulation signal, but is converted to the phase modulation modulation frequency with the resonance frequency of the cantilever 2 as the carrier frequency by the interaction between the probe 10 and the magnetic field. Therefore, the maximum value of the frequency (ωm) is the resonance frequency of the cantilever 2 (corresponding to the vibration frequency of the probe 10).
It has been confirmed by experiments that the measurement depends on the cutoff frequency of the low-pass filter in the phase detector and must be 1/10 or less of the resonance frequency (ωr) to measure with high sensitivity.

A magnetic field (recording magnetic field) is generated from the gap of the recording head 3 in response to the supply of the signal current 104.
When the probe 10 is brought close to the recording head 3 in this state,
A mechanical interaction due to a magnetic field acts on the probe 10 (step S2).

In this measurement, it is desirable to compare the surface shape (concavo-convex image) of sample 3 with the magnetic field saturation position. Therefore, first, the surface shape (concavo-convex image) of the sample 3 is measured.
For that purpose, the computer 20 switches the measurement operation and outputs the measurement signal 1 output from the feedback circuit 12.
Enter 01. In this case, the scanning piezoelectric element 4 changes the three-dimensional relative position and relative distance between the sample 3 and the probe 10 according to the control signal from the feedback circuit 12.

Then, a signal having a mechanical resonance frequency (ωr) of the cantilever 2 or a frequency in the vicinity thereof is supplied from the signal generator 6 to the vibration piezoelectric element 5. This allows
The vibrating piezoelectric element 5 vibrates the cantilever 2 having the probe 10 at the above frequency. In this state, the tip of the probe 10 is scanned while lightly contacting (tapping) the surface of the recording head 3.

The feedback circuit 12 includes the scanning piezoelectric element 4 so that the amplitude of the output signal 102 from the amplitude / DC voltage converter 11 is kept constant (the probe-sample distance is kept constant). Drive control. At this time, the feedback circuit 12 outputs the drive control signal to the computer 20 as the measurement signal 101 of the surface shape (concavo-convex image) of the recording head 3 (step S3).

Next, among the mechanical interactions acting on the probe 10, the one synchronized with the AC component (strictly different, but equivalent to the one obtained by differentiating the magnetic field with the DC current) is used as the frequency demodulator 2.
1 and through the synchronous detector 9.

The mechanical interaction acting on the probe 10 (that is, the magnetic field of the recording head) is detected by the frequency demodulator 21 as a resonance frequency change (frequency shift) of the cantilever 2. Further, the synchronous detector 9 converts the signal synchronized with the AC (alternating current) component of the mechanical interaction into the measurement signal 100.
Is output as. The measurement signal 100 is an amplitude component synchronized with the frequency (ωm) of the alternating current, and corresponds to a magnetic field-current differential value dH / dI obtained by differentiating the magnetic field H generated from the recording head with the current I.

The computer 20 causes the probe 10 to scan the range of the gap of the recording head 3 so that the magnetic field--
A measurement signal 100 for measuring a differential current image is input (step S4).

The computer 20 executes predetermined signal processing on the measurement signal 100 obtained from the measuring apparatus main body 1 to convert the magnetic field-current differential image of the recording head 3 as the measurement result into image data with black contrast. Convert. By displaying and outputting this image data on the screen of the display, the magnetic field characteristics of the recording head 3 to be measured (saturation phenomenon)
It becomes possible to observe directly.

In this way, the magnetic field-current differential image (measurement signal 100) which is the magnetic field characteristic of the recording head 3 to be measured and the unevenness image (measurement signal 101) which is the surface shape are measured by the measuring device main body 1 and the computer 20. To be measured.

In this example, since it is difficult to simultaneously measure the unevenness image and the magnetic field-current differential image, the measurement operation is switched to measure the unevenness image (step S3) and the magnetic field-current differential image. The measurement (step S4) is performed separately.

Next, when the DC current is changed and the same measurement is performed again (step S5), the setting of the DC current value is changed (step S6), and the steps S3 and S are performed.
Repeat step 4. When there is no need to change the DC current to perform the measurement, the process ends.

By thus obtaining the measurement results corresponding to various current values, the magnetic field-current differential curve (image), and further, the magnetic field-current curve (image) is obtained from this magnetic field-current differential curve (image). , Can be obtained on the computer 20.

FIG. 3 is a diagram for explaining the magnetic field-current differential value obtained in the same embodiment.

Magnetic field-current differential value dH obtained in this embodiment
/ dI varies depending on the location (each part) of the recording head (site
dependence).

As shown in FIG. 3A, of the magnetic poles P1 and P2 of the recording head, for example, three positions on the magnetic pole P2 side (gap edge center portion (circle), corner portion (square), P2 in the figure). Consider the measurement of the magnetic pole boundary (triangle). Fig. 3 shows the current dependence of the force gradient (hereinafter referred to as dH / dI force gradient) due to dH / dI at the above three locations in this case.
It shows in (B).

As shown in FIG. 3B, in the gap edge center, dH / dI is constant up to about 10 mA, so it can be seen that saturation begins around 10 mA. At the corners, the dH / dI force gradient attenuates uniformly from the low current, indicating that saturation has already begun even at low current values. At the boundary of the P2 magnetic pole, the dH / dI force gradient is smaller than the other two, so it can be seen that the magnetic field strength gradient with respect to the current is small. further
Since it is flat up to about 15mA, it can be seen that it increases monotonously up to 15mA and then begins to saturate. As described above, the above measurement results showed that the saturation phenomenon of the recording head was different depending on the location.

As described above, in this embodiment, it is possible to measure the magnetic field-current differential image and the surface shape (concavo-convex image) of the recording head 3 which is the object of measurement. Therefore, computer 2
With 0, by generating an image from the magnetic field-current differential image of the recording head 3 which is the measurement result, it becomes possible to visually observe the magnetic field characteristics (magnetic field saturation phenomenon) of the recording head 3. In addition, a magnetic field-current differential curve (image) for the recording head 3 and further a magnetic field-current curve (image) are calculated from the measurement result obtained by changing the current value (DC current value), thereby performing measurement with high resolution. You can make an evaluation.

Particularly, in this embodiment, the frequency detection method is applied to the magnetic field saturation measurement of the recording head, and the vibration of the cantilever 2 is feedback-controlled by the positive feedback oscillation system and the phase shifter 22 adjusts the phase change. As a result, it becomes possible to effectively improve the Q value of the cantilever 2 and to stably and highly sensitively capture the magnetic field saturation phenomenon.

(Modification 1) FIG. 4 is a view showing a modification of the magnetic head measuring apparatus shown in FIG. The same elements as those in FIG. 1 are designated by the same reference numerals, and the detailed description thereof will be omitted.

In the magnetic head measuring device of FIG. 1 described above,
Although the amplitude / DC voltage converter 11 is provided, this modification does not use the amplitude / DC voltage converter.

In the magnetic head measuring device of FIG. 1 described above, the output signal of the amplitude / DC voltage converter 11 is sent to the feedback circuit 12, but in this modification, the amplitude / DC voltage converter 11 is used. Is not used, the output signal of the frequency demodulator 21 is instead sent to the feedback circuit 12 (in addition to being sent to the synchronous detector 9).

By using the output signal 104 of the frequency demodulator 21, the feedback circuit 12 uses the signal 103 for driving and controlling the piezoelectric element 4 for scanning and the sample 3 as in the case of the magnetic head measuring apparatus of FIG. It is possible to generate the measurement signal 101 of the surface shape (concavo-convex image) of.
In this case, the feedback circuit 12 uses the frequency demodulator 2
While controlling the drive of the scanning piezoelectric element 4 so that the amplitude of the output signal 104 from 1 is kept constant (to a value set in advance) (the probe-sample distance is kept constant). The drive control signal is output to the computer 20 as a measurement signal 101 of the surface shape (concavo-convex image) of the sample 3.

In this way, the feedback circuit 12
When measuring the surface shape (concavo-convex image) of the sample 3, the output signal 104 of the frequency demodulator 21 is used. This output signal 1
The characteristic of No. 04 is shown in FIG. 5 (curve a). This output signal is
When the probe-sample distance is large, the contribution from the recording magnetic field is dominant (broken line b), but when the probe-sample distance is small (several nm), the contribution from van der Waals force is large. It becomes dominant (dashed line c). The van der Waals force is generated by the orbital reconstruction of the electrons around the atom, so if this signal is used as the input signal for feedback and feedback control is performed so that the frequency shift due to the van der Waals force becomes constant. The surface shape of the sample 3 can be measured. However, as shown in the following equation, the magnetic interaction Fmag is the van der Waals force Fv.
It is necessary to perform the measurement under the condition that the distance is smaller than dw (in the region where the probe-sample distance is several nm).

[0069]

[Equation 2]

In this modification, as in the case of FIG. 1, even if the arrangement order of the AGC circuit 23 and the phase shifter 22 is exchanged, there is no problem in measurement.

The measurement procedure in this modification is almost the same as the measurement procedure described with reference to FIG.
However, in this modification, it is also possible to simultaneously measure the unevenness image and the magnetic field-current differential image in the same field of view, and measure the unevenness image (step S3 in FIG. 2) and the magnetic field-current differential image. (Step S4 in FIG. 2) may be performed at the same time, or the unevenness image and the magnetic field-current differential image may be separately measured.

(Modification 2) FIG. 6 is a diagram for explaining a modification of the measuring method in the present embodiment. The measuring method according to this example can be applied to both the measuring apparatus having the configuration shown in FIG. 1 and the measuring apparatus having the configuration shown in FIG.

In FIG. 6, the probe 10 for the recording head 3 is shown.
The scanning range 400, the scanning line 401 (broken line), and the measurement position 402 (black circle) are conceptually shown.

In the measuring method of this example, the probe 10 is scanned around the magnetic poles P1 and P2 of the recording head 3 (gap 30) in the scanning range 400 (scan line 401).
The scan is temporarily stopped at the preset measurement position 402. Then, the signal current 10 supplied to the recording head 3
The computer 20 stores the measurement result (magnetic field-current differential value) from the synchronous detector 9 when the current value (DC current value) 4 is changed. The computer 20 analyzes a plurality of measurement results (magnetic field-current differential value) obtained by changing the DC current value, and calculates a magnetic field-current differential curve. Further, the computer 20 moves the probe 10 to a predetermined measurement position 4
The magnetic field-current curve of the recording head 3 is calculated from the magnetic field-current differential curve for each 02.

According to such a modification, the scanning of the probe 10 and the change of the DC current value can be executed simultaneously, so that the magnetic field-current differential curve and the magnetic field-current curve can be calculated in a short time. It becomes possible to do.

The present invention is not limited to the above-described embodiments, but can be implemented with various modifications without departing from the scope of the invention.

[0077]

As described in detail above, according to the present invention, a magnetic head measuring apparatus for measuring the magnetic field characteristics of a recording head included in a magnetic head using a magnetic force microscope (MFM) is used. By converting the obtained magnetic field-current differential image into an image by a predetermined signal processing, it becomes possible to visually observe the saturation phenomenon of the magnetic field from the magnetic pole edge of the recording head to be measured. Further, by changing the current value supplied to the recording head, it becomes possible to obtain the current dependency (magnetic field-current curve) on the magnetic field of the recording head. That is, it is possible to directly and with high resolution observe the saturation magnetic field, which is the magnetic field characteristic of the recording head to be measured, and consequently improve the measurement performance of the recording head.

[Brief description of drawings]

FIG. 1 is a block diagram showing a main part of a magnetic head measuring device according to an embodiment of the present invention.

FIG. 2 is a flowchart for explaining a measurement procedure according to the same embodiment.

FIG. 3 is a diagram for explaining a magnetic field-current differential value obtained in the same embodiment.

FIG. 4 is a view showing a modified example of the magnetic head measuring device of FIG. 1.

FIG. 5 is a diagram for explaining characteristics of an output signal of the frequency demodulator used in the same embodiment.

FIG. 6 is a view for explaining a modified example of the measuring method according to the same embodiment.

[Explanation of symbols]

1 ... Measuring device body 2 ... cantilever 3 ... Sample (recording head) 4 ... Scanning piezoelectric element member 5 ... Piezoelectric element for vibration 7 ... Displacement detector 9 ... Synchronous detector 10 ... Tip 11 ... Amplitude / DC voltage converter 12 ... Feedback circuit 13 ... Signal generator 20 ... Computer 21. Frequency demodulator 22 ... Phase shifter 23 ... AGC circuit

Claims (11)

[Claims] 1. A magnetic head measuring device for measuring at least one measurement point on a recording head, comprising a magnetic body at least in part, and a probe for scanning the measurement point. A cantilever that supports the probe, a vibrating unit that vibrates the cantilever, a displacement detecting unit that detects a displacement of the cantilever vibrated by the vibrating unit, and a detection result of the displacement detecting unit. A vibration control means for controlling the cantilever to vibrate the cantilever at a predetermined frequency and amplitude; and a current obtained by applying a direct current and an alternating current to the recording head, Current applying means for generating a magnetic field from the recording head, and a magnetic interaction generated by the recording head according to the current applied by the current applying means with respect to the mechanical interaction exerted on the probe. The magnetic head measuring apparatus characterized by signal comprises a signal detecting means for detecting the vibration frequency change in the cantilever. 2. The magnetic head measuring device according to claim 1, wherein the signal detecting means has means for extracting an amplitude component in synchronization with an alternating current from the vibration frequency change of the cantilever. 3. The magnetic head measuring device according to claim 1, further comprising a measuring unit that measures the direct current value dependency of the signal detected by the signal detecting unit. 4. The measuring means obtains a magnetic field-current differential curve at an arbitrary measuring point on the recording head based on a signal obtained from the detecting means by changing the direct current in the current applying means. The magnetic head measuring device according to claim 1, wherein 5. The vibration control means outputs a signal obtained by changing a phase of vibration of the cantilever based on a detection result of the displacement detection means, and an output signal of the phase shifter. 2. The magnetic head measuring apparatus according to claim 1, further comprising: an automatic gain control circuit that outputs a signal for keeping the amplitude of vibration of the cantilever constant. 6. The magnetic head measuring apparatus according to claim 1, wherein the frequency of the alternating current in the current applying means is set to be lower than the vibration frequency in the vibrating means. 7. The measuring means changes the direct current in the current applying means in a state in which scanning by the probe is stopped at an arbitrary measuring point on the recording head, whereby the detecting means changes the direct current. 2. The magnetic head measuring device according to claim 1, wherein a process of obtaining a magnetic field-current differential curve at the measurement point is performed for each of the plurality of measurement points based on the obtained signal. 8. A signal converting means for converting an amplitude value of an AC signal from an output signal of the displacement detecting means into a DC signal and outputting the DC signal, and the probe and the recording based on the DC signal obtained from the signal converting means. Control means for generating a drive control signal for scanning while keeping a constant distance from the surface of the head, and for generating the drive control signal as a measurement signal of the surface shape of the recording head. The magnetic head measuring device according to claim 1, wherein: 9. A drive control signal for scanning with a constant distance between the probe and the surface of the recording head is generated based on a vibration frequency change of the cantilever detected by the signal detecting means. Along with this, it further comprises control means for generating the drive control signal as a measurement signal of the surface shape of the recording head.
The magnetic head measuring device described. 10. The magnetic head measuring device according to claim 1, wherein the alternating current in the current applying means is an amplitude modulation current amplitude-modulated with a predetermined carrier frequency and a modulation frequency. 11. A measuring method applied to a magnetic head measuring device for measuring at least one measuring point on a recording head, wherein a current obtained by combining a direct current and an alternating current is applied to the recording head. By applying a magnetic field from the recording head and controlling the cantilever supporting the probe for scanning the measurement point to be excited at a predetermined frequency and amplitude, the recording of the probe is performed. A signal corresponding to a mechanical interaction exerted on the probe by a magnetic field generated from the recording head in response to the current application,
A measuring method comprising detecting as a vibration frequency change of the cantilever.