JP3597787B2 - Magnetic recording head measuring device and magnetic recording head measuring method - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a magnetic recording head measuring apparatus and a magnetic recording head measuring method for measuring the characteristics of a magnetic recording head, and more particularly, to the frequency of a high-frequency magnetic field of a magnetic recording head using a technique of a magnetic force microscope (MFM). The present invention relates to a magnetic recording head measuring device and a magnetic recording head measuring method for measuring characteristics.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, in a manufacturing process of a magnetic recording head used for a hard disk drive (HDD), for example, when measuring a magnetic field distribution and a magnetic force of the head, a dedicated head measuring device using a magnetic force microscope (MFM) Is used. The MFM is a type of scanning probe microscope. Usually, a probe mounted on a cantilever is brought close to a magnetic recording head, which is a sample to be measured, and magnetic force interaction caused by a magnetic field generated from the head in a non-contact state ( Force or force gradient).
[0003]
A magnetic recording head (hereinafter sometimes simply referred to as a head) is, for example, an inductive type thin film head, and has a magnetic gap for generating a recording magnetic field according to a signal current applied to a coil. The magnetic recording head measuring device applies a high-frequency signal current to a (head coil) as a sample, and measures a magnetic field distribution generated from the magnetic gap. As a specific measuring method, the phase or displacement of the vibrating cantilever (magnetic force interaction caused by the magnetic field of the head) is detected, and a force gradient or force acting between the probe and the sample is determined based on the detection result. Is measured. In this case, the measurement is performed using the relationship that the phase of the cantilever approximates a force gradient and the displacement of the cantilever approximates a force.
[0004]
By the way, there are various measuring methods. For example, "Measuring the gigahertz response of recording heads with the magnetic force microscopy", R.A. See Proksch et al. (Digital Instruments et al.), Applied Physics Letters, Vol. 74, No. 9, March 1999, pp 1308-1310 (hereinafter, referred to as prior art 1), a current was amplitude-modulated to a magnetic recording head, and the modulation frequency was adjusted to the resonance frequency of the MFM cantilever to vibrate. A technology for detecting a resonance frequency component of a displacement (force) of a cantilever is disclosed. In this technique, sensitivity is improved by utilizing the Q value of the mechanical resonance frequency of the cantilever.
[0005]
Also, "Evaluation and analysis technology for recording and reproducing heads", Hiroyuki Omori, Sony Corporation, Journal of the Japan Society of Applied Magnetics, vol. 23, No. 12, 1999, pp2111-12117 (hereinafter referred to as Prior Art 2), a high frequency sine wave is applied to a magnetic recording head, and a DC component of a phase change (force gradient) of a cantilever due to a magnetic field generated around the head. A technique for measuring is disclosed.
[0006]
[Problems to be solved by the invention]
The above-mentioned prior arts 1 and 2 are effective methods in principle, but are mainly for measuring the spatial distribution of the magnetic field of the head, and the frequency characteristics of the high-frequency magnetic field in a state of being incorporated in an actual HDD Not suitable for measurement of The reason lies in the difference in the signal application method between the signal generator and the amplifier that drives the head. The signal generator is usually driven at a constant voltage, but the actual head amplifier is driven at a constant current (however, it may not be constant at high frequencies due to frequency characteristics). When a signal is directly applied from a signal generator, the impedance of the circuit meter changes at a high frequency, so that it is impossible to measure a frequency characteristic close to a state of being incorporated in the HDD. Further, since an actual head amplifier operates digitally, it is difficult to incorporate the head amplifier into the devices of Prior Art 1 and Prior Art 2.
[0007]
SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and is capable of measuring a frequency characteristic of a magnetic field generated from a magnetic recording head in an environment similar to a state where the magnetic recording head is incorporated in an HDD. It is an object to provide a measuring device and a magnetic recording head measuring method.
[0008]
[Means for Solving the Problems]
A magnetic recording head measuring device according to the present invention is a magnetic recording head measuring device for measuring characteristics of a magnetic recording head, wherein the probe scans the surface of the magnetic recording head in a non-contact state, and vibrates the probe. Vibrating means,Generate an amplitude-modulated signal obtained by amplitude-modulating a carrier and change the carrier frequency.A signal generating unit, and a head having an electrical characteristic equivalent to that of an actual head drive amplifier, generating an amplitude modulation current for operating the magnetic recording head based on the amplitude modulation signal, and applying the amplitude modulation current to the magnetic recording head An amplifier equivalent circuit, phase displacement measuring means for measuring the phase displacement of the vibration of the probe according to the magnetic field generated from the magnetic recording head, and the signal generating meansCarrier frequencyMagnetic field frequency dependency measuring means for measuring the change in the phase displacement with respect to the change in the magnetic field as the magnetic field frequency dependency of the magnetic recording head.
[0009]
Further, a magnetic recording head measuring apparatus according to the present invention is a magnetic recording head measuring apparatus for measuring characteristics of a magnetic recording head, and a head amplifier equivalent circuit having electric characteristics equivalent to an actual head driving amplifier.And a signal generator and a current amplitude measuring device, and the signal frequency of the head amplifier equivalent circuit to which the magnetic recording head is connected is changed while the amplitude is maintained at a constant value from the signal generator. The input signal is input, and the amplitude of the current supplied to the magnetic recording head is measured using the current amplitude measuring device.Current frequency dependence measuring means, a probe for scanning the surface of the magnetic recording head in a non-contact state, and a vibration means for vibrating the probe,Generating an amplitude-modulated signal obtained by amplitude-modulating a carrier wave;While applying to the magnetic recording head as an amplitude modulation current for operating the magnetic recording head,Change the carrier frequencyA signal generating unit, a phase displacement measuring unit for measuring a phase displacement of vibration of the probe according to a magnetic field generated from the magnetic recording head,Carrier frequencyMagnetic field frequency dependency measuring means for measuring the change in the phase displacement with respect to the change in the magnetic field as the magnetic field frequency dependency of the magnetic recording head.
[0010]
The magnetic recording head measuring method according to the present invention is a magnetic recording head measuring method for measuring characteristics of a magnetic recording head, wherein a surface of the magnetic recording head is scanned in a non-contact state with a probe vibrated. Steps toGenerate an amplitude-modulated signal obtained by amplitude-modulating a carrier and change the carrier frequency.Applying the amplitude modulation signal to a head amplifier equivalent circuit having an electrical characteristic equivalent to that of an actual head drive amplifier; and generating an amplitude modulation current for operating the magnetic recording head from the head amplifier equivalent circuit. Applying to the magnetic recording head, measuring the phase displacement of the vibration of the probe according to the magnetic field generated from the magnetic recording head,Carrier frequencyMeasuring the change in the phase displacement with respect to the change in the magnetic field as the magnetic field frequency dependency of the magnetic recording head.
[0011]
A magnetic recording head measuring method according to the present invention is a magnetic recording head measuring method for measuring characteristics of a magnetic recording head, and comprises a head amplifier equivalent circuit having electric characteristics equivalent to an actual head driving amplifier.Using a signal generator and a current amplitude measuring device, and changing the signal frequency of the head amplifier equivalent circuit to which the magnetic recording head is connected while maintaining the amplitude at a constant value from the signal generator. And the amplitude of the current supplied to the magnetic recording head is measured using the current amplitude measuring device.Scanning the surface of the magnetic recording head in a non-contact state with the probe vibrated,Generating an amplitude-modulated signal obtained by amplitude-modulating a carrier wave;While applying to the magnetic recording head as an amplitude modulation current for operating the magnetic recording head,Change the carrier frequencyMeasuring the phase displacement of the vibration of the probe according to the magnetic field generated from the magnetic recording head;Carrier frequencyMeasuring the change in the phase displacement with respect to the change in the magnetic field as the magnetic field frequency dependency of the magnetic recording head.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0013]
<First embodiment>
First, a first embodiment of the present invention will be described.
(Configuration of magnetic recording head measuring device)
FIG. 1 is a block diagram showing a main part of a magnetic recording head measuring device according to the first embodiment of the present invention.
[0014]
As shown in FIG. 1, the measuring apparatus according to the embodiment includes a magnetic recording head 101 as an object to be measured, a head amplifier equivalent circuit 102 for applying a current to the magnetic recording head 101, a carrier frequency ωc and a modulation frequency ωm. A current that generates an amplitude-modulated signal and flows through the head amplifier equivalent circuit 102AmplitudeA signal generator 103 for controlling the frequency and a current flowing through the magnetic recording head 101AmplitudeAnd a probe 106 as a vibrator made of a magnetic material or coated with a magnetic material and magnetized to measure a high-frequency magnetic field generated from the magnetic recording head 101. It has a mechanical interaction measuring system 107 for measuring a mechanical interaction acting on the needle 106, and a signal processing device 108 for storing and processing one or more signals output from the mechanical interaction measuring system 107. .Hereinafter, “current amplitude” is referred to as “current value”.
[0015]
Further, the measuring device includes a cantilever 111 that supports the probe 106, a vibrating piezoelectric element 112 that vibrates the cantilever 111 at a mechanical resonance frequency ωr (or a frequency in the vicinity thereof), and a vibrating piezoelectric element 112. And a signal generator 113 for giving a signal of a mechanical resonance frequency ωr (or a frequency in the vicinity thereof) to the signal generator 113.
[0016]
In particular, in the measuring device of the present embodiment, the probe 106, the cantilever 111, the vibrating piezoelectric element 112, the mechanical interaction measuring system 107, and the like constitute the force measuring device 109. , A magnetic recording head 101, a head amplifier equivalent circuit 102, a signal generator 103, a current value measuring device 104, etc., constitute a magnetic head characteristic evaluation device 114.
[0017]
The magnetic head characteristic evaluation device 114 can extract an amplitude component synchronized with the modulation frequency of the amplitude modulation of the mechanical interaction measured by the mechanical interaction measurement system 107, and thereby, the magnetic field of the magnetic field depending on the carrier frequency can be extracted. The ingredients can be obtained.
[0018]
The force measuring device 109 has a function of scanning the probe 106 three-dimensionally, a function of measuring a mechanical interaction acting on the probe 106 by a high-frequency magnetic field, and a function of measuring the surface shape of the magnetic recording head 101. These functions can be realized by diverting a commercially available or self-made scanning probe microscope (SPM).
[0019]
FIG. 2 shows components in the magnetic head characteristic evaluation device 114 in more detail.
[0020]
That is, in addition to the above-described elements, the measuring device of the present embodiment includes a displacement detector 115 for detecting the displacement of the cantilever 111, a signal generated from the signal generator 113, and a signal output from the displacement detector 115. A phase detector 116 for detecting a difference in phase and measuring a force gradient acting on the probe 106, a synchronous detector 117 for measuring an AC component of the phase detector 116, and an AC signal output from the displacement detector 115 / DC voltage converter (RMS-DC circuit) 118 which outputs the amplitude of the signal as a DC signal, a feedback circuit 119 for making the output of the amplitude / DC voltage converter 118 constant, a probe 106 and a magnetic head And a scanning piezoelectric element 120 for changing a three-dimensional relative position with respect to 101. These elements are provided in the force measuring device 109 in FIG.
[0021]
The signal processing device 108 not only stores the obtained data, but also controls and monitors the magnetic head characteristic evaluation device 114 including the force measuring device 109. Further, it has a function that can collectively store measurement conditions and measurement data of the magnetic head characteristic evaluation device 114, and can perform data analysis even after an experiment.
[0022]
In particular, in the present embodiment, since a circuit equivalent to a head amplifier (a kind of voltage-current converter) can be driven at a high frequency, the frequency characteristics of the magnetic recording head are reduced, and the electrical characteristics (wiring of the head amplifier and the slider portion are also reduced). The characteristics can be measured separately from magnetic characteristics (the characteristics of the magnetic material of the head).
[0023]
(Measuring method)
Hereinafter, the measurement method of the embodiment will be described with reference to the flowcharts of FIGS. 3 and 4 together with FIG.
[0024]
The measurement of the frequency characteristics of the magnetic recording head according to the present embodiment is performed according to the processing shown in FIGS. The processing in FIG. 3 includes (1) head magnetic field frequency dependency (that is, phase shift-frequency characteristic) in an environment close to a state where the magnetic recording head is incorporated in the HDD, and (2) a current value flowing through the magnetic recording head. (I.e., current-frequency characteristics) can be measured. On the other hand, in the processing in FIG. 4, (3) the frequency dependency (that is, phase shift-frequency characteristic) of the magnetic recording head portion (mainly related to the magnetic material) can be measured.
[0025]
First, in FIG. 3, the magnetic recording head 101 as an object to be measured is arranged at a predetermined measurement position. The carrier frequency CF (ωc), modulation frequency MF (ωm), and amplitude of the amplitude modulation signal of the signal generator 103 are set (step S101). Note that the modulation frequency MF (ωm) is set to be lower than the mechanical resonance frequency ωr of the cantilever 111.
[0026]
The amplitude modulation signal output from the signal generator 103 is applied to the head amplifier equivalent circuit 102 (step S102), and the magnetic recording head 101 generates a magnetic field.
[0027]
The probe 106 is brought close to the magnetic recording head in a non-contact state (step S103) so that the mechanical interaction due to the head magnetic field can be measured.
[0028]
The current value flowing through the magnetic recording head 101 is measured by the current value measuring device 104 (step S104), and the ωm component of the force acting on the probe 106 is measured (step S105). Here, the measurement in step S105 means (1) when the probe 106 is brought close to the magnetic recording head 101 and measurement is performed at one point without scanning the probe 106, or (2) when the probe 106 is scanned. After measuring a one-dimensional profile or a two-dimensional image, an arbitrary point may be selected and the ωm component at that location may be used as a measured value.
[0029]
When the measurement is performed at another carrier frequency CF (ωc), the carrier frequency CF of the amplitude modulation signal of the signal generator 103 is set (step S107), and the measurement of steps S104 and S105 is repeated.
[0030]
From the results at the respective frequencies, (1) the head magnetic field frequency dependence 201 in a state close to the state where the magnetic recording head is incorporated in the HDD device, and (2) the frequency dependence 202 of the current value flowing through the magnetic recording head, Obtained (Step S108).
[0031]
Next, in FIG. 4, the magnetic recording head 101, which is an object to be measured, is arranged at a predetermined measurement position, and the carrier frequency CF (ωc), modulation frequency MF (ωm), and amplitude of the amplitude modulation signal of the signal generator 103 are set. Is set (step S201). Note that the modulation frequency MF (ωm) is set to be lower than the mechanical resonance frequency ωr of the cantilever 111.
[0032]
The amplitude modulation signal output from the signal generator 103 is applied to the head amplifier equivalent circuit 102 (step S202), and the magnetic recording head 101 generates a magnetic field.
[0033]
The probe 106 is brought close to the magnetic recording head in a non-contact state (step S203) so that the mechanical interaction due to the head magnetic field can be measured.
[0034]
The amplitude of the signal generator 103 is adjusted so that the current flowing through the magnetic recording head 101 becomes equal to a predetermined value (step S204), and the ωm component of the force acting on the probe 106 is measured (step S205). ). Here, the measurement in step S205 means (1) when the probe 106 is brought close to the magnetic recording head 101 and measurement is performed at one point without scanning the probe 106, or (2) when the probe 106 is scanned. After measuring a one-dimensional profile or a two-dimensional image, an arbitrary point may be selected and the ωm component at that location may be used as a measured value.
[0035]
When the measurement is performed at another carrier frequency CF (ωc) (step S206), the carrier frequency CF of the amplitude modulation signal of the signal generator 103 is set (step S207), and the measurement at steps S204 and S205 is repeated.
[0036]
From the results at the respective frequencies, (3) the head magnetic field frequency dependency 301 reflecting only the characteristics of the magnetic recording head portion is obtained (step S208).
[0037]
FIG. 5 is a diagram for explaining a measurement position and the like in the magnetic recording head. On the other hand, FIGS. 6A and 6B are graphs 501 and 502 corresponding to the head magnetic field frequency dependency 201 and the head current frequency dependency 202 obtained by the processing of FIG. 3, respectively. FIG. 7 is a graph 601 corresponding to the head magnetic field frequency dependency 301 obtained by the processing of FIG. The measurement position in this case corresponds to the gap center 403 of the P2 magnetic pole 402 in the magnetic recording head gap in FIG. The “phase shift” in the graph 501 of FIG. 6A and the graph 601 of FIG. 7 is a unit indicating the strength of the magnetic field in the MFM measurement, and the larger the value, the larger the magnetic field strength.
[0038]
In the graph 501 of FIG. 6A, it can be seen that there is no change in the phase shift in the frequency range of 5 to 20 MHz, and a uniform magnetic field is generated. The phase shift decreases from around 50 MHz and reaches a local minimum around 100 MHz. Further, it becomes maximum around 230 MHz, and attenuates at frequencies after that. In the graph 502 of FIG. 6B, there is no local minimum value, but the local maximum value is recognized at the same frequency as the graph 501 of FIG. 6A. On the other hand, in the graph 601 in FIG. 7, there is no minimum / maximum value as in the graph 501 in FIG. 6A, and the phase shift decreases as the frequency increases. The rate of decrease increases as the frequency increases.
[0039]
Here, the reason why the head magnetic field frequency dependency 201 in a state close to a state where the magnetic recording head is incorporated in the HDD device has the characteristic shown in the graph 501 of FIG. A graph 501 in FIG. 6A shows the measurement results of the frequency characteristics including the head amplifier and the wiring / magnetic recording head, and a graph 601 in FIG. 7 shows the measurement results of the frequency characteristics of the head portion. Considering that the frequency characteristic of the current value in the graph 502 of FIG. 6B is an electrical frequency characteristic of the head amplifier equivalent circuit 102, wiring, and the like, the frequency characteristic of the graph 601 of FIG. 6) is expected to be equal to the characteristic in the graph 501 of FIG. 6A.
[0040]
A graph 701 in FIG. 8 shows a result obtained by multiplying the frequency characteristic in the graph 601 in FIG. 7 by the frequency characteristic in the graph 502 in FIG. 6B. It can be seen that the frequency characteristic of the graph 701 in FIG. 3 is substantially equal to the frequency characteristic of the graph 501 in FIG. Thus, in the measurement method according to the present embodiment, the frequency dependency can be measured separately from the magnetic characteristics (graph 601 in FIG. 7) and the electric characteristics (graph 502 in FIG. 6B), and these can be measured. It has been proved that the combined characteristics, that is, the magnetic field frequency dependence of the head in a state close to the state in which the magnetic recording head is incorporated in the HDD device (graph 501 in FIG. 6A) can be measured.
[0041]
FIG. 9 shows a profile of a change in magnetic field contrast due to a difference in frequency when measurement is performed by the method shown in FIG. The profile corresponds to the result at the pole edge portion 404 of the P1 pole 401 in the magnetic recording head gap of FIG. 5, and the dotted line 801 and the solid line 802 show the results when the frequency is 10 MHz and 350 MHz, respectively. When the frequency is 350 MHz, the magnetic field strength decreases as shown by the dependence in the graph 501. Further, it can be seen that not only a decrease in the magnetic field but also a peak occurs at the edge corner, and the contrast is also changed. This is presumably because the higher the frequency, the lower the magnetic field intensity at the center due to the skin effect. As described above, the characteristics of the magnetic recording head at an arbitrary frequency can be measured with high resolution, and a change in contrast or intensity due to a difference in frequency can be analyzed.
[0042]
According to the above-described first embodiment, it is possible to measure the frequency characteristics of the magnetic field generated from the magnetic recording head in almost the same environment as when the magnetic recording head is incorporated in the HDD.
[0043]
In addition, the frequency characteristics of the magnetic recording head portion (with the influence of the wiring and the head amplifier removed) can be measured.
[0044]
Further, the frequency characteristics of the magnetic recording head can be measured separately from electrical characteristics and magnetic characteristics.
[0045]
Further, the characteristics of the magnetic recording head at an arbitrary frequency can be measured with high resolution, and changes in contrast and intensity due to a difference in frequency can be analyzed.
[0046]
Further, not only the gap position of the magnetic recording head but also the frequency dependency of a magnetic field (leakage magnetic field) generated around the gap can be measured, and the influence of a high-frequency leakage magnetic field on an adjacent track can be predicted.
[0047]
Further, at an arbitrary frequency, the absolute value of the impedance can be measured from the applied voltage of the signal generator and the measured current value.
[0048]
In addition, the signal processing device not only stores the obtained data but also controls and monitors the magnetic head characteristic evaluation device including the force measuring device. Further, the measurement conditions and measurement data of the magnetic head characteristic evaluation device can be collectively stored, and the data can be analyzed even after the experiment.
[0049]
<Second embodiment>
Next, a second embodiment of the present invention will be described.
(Configuration of magnetic recording head measuring device)
This embodiment measures the frequency characteristic in the same manner as the first embodiment described above, but differs from the first embodiment in that the frequency dependence of the current value flowing through the magnetic recording head is measured in advance. By doing so, the frequency characteristics of the magnetic recording head can be obtained without incorporating a head amplifier equivalent circuit in the magnetic head characteristic evaluation device.
[0050]
When the frequency dependence of the current value is measured in advance, the measurement can be performed using a digitally driven head amplifier used in actual HDD measurement. For this reason, a measurement result in a state closer to the state of being incorporated in the HDD device can be obtained.
[0051]
When a head amplifier equivalent circuit is incorporated in a magnetic head characteristic evaluation device for measurement, it is desirable to flow a positive / negative (that is, a current value crosses zero and has no offset current) high-frequency current in order to approach an actual HDD state. However, when a head amplifier equivalent circuit that satisfies such a condition is configured, it is difficult to widen the band. On the other hand, in the state including the offset current, it is relatively easy to widen the band of the head amplifier equivalent circuit. However, in this case, an offset magnetic field is also generated in the magnetic recording head, and the magnetic field is saturated in a part of the magnetic recording head, so that it is difficult to measure a high-frequency magnetic field using the MFM. Therefore, by measuring the frequency dependence of the current value in advance by using a head amplifier equivalent circuit including an offset current and performing the measurement by the method described below, it is possible to perform measurement in a very high frequency band.
[0052]
FIG. 10A is a diagram illustrating a circuit configuration of an apparatus for measuring the frequency dependence of a current value in advance. The device shown in FIG. 10A includes the same components as the magnetic recording head 101, the head amplifier equivalent circuit 102, the signal generator 103, and the current value measuring device 104 in FIG. Since each element is as described above, a specific description is omitted. FIG. 10B is a graph showing the frequency dependence of the current value as a result of measurement using the apparatus of FIG.
[0053]
FIG. 11 is a block diagram showing a main part of a magnetic recording head measuring device according to the second embodiment of the present invention. This measuring device is used for measuring the frequency dependence of a magnetic force caused by a high-frequency magnetic field after measuring the frequency dependence of a current value using the device of FIG. In FIG. 11, the same components as those in FIG. 1 are denoted by the same reference numerals, and a specific description thereof will be omitted.
[0054]
The measuring device shown in FIG. 11 is different from FIG. 1 in that the head amplifier measuring device is not incorporated, and the signal generated from the signal generator 103 is directly applied to the magnetic recording head 101. Other configurations are the same as those described in the first embodiment.
[0055]
(Measuring method)
Hereinafter, the measurement method of the embodiment will be described with reference to the flowchart of FIG. 12 together with FIGS. 10 and 11.
[0056]
The frequency dependence of the current value is measured in advance by the device shown in FIG. Specifically, the frequency of the signal generator 103 is changed, and the current value of the current value measuring device 104 is read and stored. As a result, the frequency dependence of the current value as shown in FIG. 10B is obtained.
[0057]
The measurement of the frequency characteristic of the magnetic recording head in the present embodiment is performed according to the processing shown in FIG. 12 and the above-described FIG. The processing in FIG. 12 includes (1) head magnetic field frequency dependence (that is, phase shift-frequency characteristics) in an environment close to a state where the magnetic recording head is incorporated in the HDD, and (2) a current value flowing through the magnetic recording head. Can be measured. On the other hand, in the processing in FIG. 4, (3) the frequency dependency (that is, phase shift-frequency characteristic) of the magnetic recording head portion (mainly related to the magnetic material) can be measured.
[0058]
First, in FIG. 12, the magnetic recording head 101 as an object to be measured is arranged at a predetermined measurement position, and the carrier frequency CF (ωc), modulation frequency MF (ωm), and amplitude of the amplitude modulation signal of the signal generator 103 are set. It is set (step S301). Note that the modulation frequency MF (ωm) is set to be lower than the mechanical resonance frequency ωr of the cantilever 111.
[0059]
The amplitude modulation signal output from the signal generator 103 is applied to the magnetic recording head 101 (step S302), and the magnetic recording head 101 generates a magnetic field.
[0060]
The probe 106 is brought close to the magnetic recording head in a non-contact state (step S303) so that the mechanical interaction due to the head magnetic field can be measured.
[0061]
The current value flowing through the magnetic recording head 101 is measured by the current value measuring device 104, and the output of the signal generator 103 is adjusted so that a predetermined current value flows (step S304).
[0062]
Then, the ωm component of the force acting on the probe 106 is measured (step S305). Here, the measurement in step S305 means (1) when the probe 106 is brought close to the magnetic recording head 101 and measurement is performed at one point without scanning the probe 106, or (2) when the probe 106 is scanned. After measuring a one-dimensional profile or a two-dimensional image, an arbitrary point may be selected and the ωm component at that location may be used as a measured value.
[0063]
When measuring at another carrier frequency CF (ωc), the carrier frequency CF of the amplitude modulation signal of the signal generator 103 is set (step S307), and the measurement of steps S304 and S305 is repeated.
[0064]
From the results at the respective frequencies, (1) the head magnetic field frequency dependence 1101 in a state close to the state where the magnetic recording head is incorporated in the HDD device, and (2) the frequency dependence 1102 of the current value flowing through the magnetic recording head. Obtained (Step S308).
[0065]
Next, measurement is performed in the same manner as in the flowchart of FIG. At this time, the same measurement can be performed even if the head amplifier equivalent circuit is not incorporated in the magnetic head characteristic evaluation device 114.
[0066]
According to the above-described second embodiment, the same effects as those of the above-described first embodiment can be obtained. In addition, before the magnetic recording head is incorporated in the magnetic head characteristic evaluation device, the frequency dependence of the current flowing through the recording head depends on the frequency. By measuring the performance in advance, it is possible to measure the frequency characteristics and the like of the magnetic recording head without providing a head amplifier equivalent circuit in the magnetic head characteristic evaluation device.
[0067]
【The invention's effect】
As described above in detail, according to the present invention, it is possible to measure the frequency characteristics of a magnetic field generated from a magnetic recording head in an environment similar to a state where the magnetic recording head is incorporated in an HDD.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a main part of a magnetic recording head measuring device according to a first embodiment of the present invention.
FIG. 2 is an exemplary view showing components in the magnetic head characteristic evaluation device of the embodiment in detail;
FIG. 3 is a flowchart illustrating a measurement method according to the embodiment.
FIG. 4 is a flowchart for explaining the measurement method according to the embodiment;
FIG. 5 is an exemplary view for explaining a measurement position and the like in the magnetic recording head of the embodiment.
FIG. 6 is a graph of a head magnetic field frequency dependency and a head current frequency dependency obtained by the processing of FIG. 3;
FIG. 7 is a graph of a head magnetic field frequency dependence obtained by the processing of FIG. 4;
8 is a diagram showing a result obtained by multiplying the frequency characteristic in the graph of FIG. 7 by the frequency characteristic in the graph of FIG.
9 is a view showing a profile of a change in magnetic field contrast due to a difference in frequency when measurement is performed by the method shown in FIG. 3;
FIG. 10 is a diagram showing a circuit configuration of an apparatus for measuring the frequency dependence of a current value in advance according to the second embodiment of the present invention, and a current obtained as a result of measurement using the apparatus. Graph of frequency dependence of values.
FIG. 11 is a block diagram showing a main part of a magnetic recording head measuring device according to a second embodiment of the present invention.
FIG. 12 is a flowchart for explaining the measurement method according to the embodiment;
[Explanation of symbols]
101: Magnetic recording head
102: Head amplifier equivalent circuit
103 ... Signal generator
104… Current value measuring device
106 ... Tip
107 ... Mechanical interaction measurement system
108 ... Signal processing device
109 ... Force measuring device
111 ... Cantilever
112: Exciting piezoelectric element
113 ... Signal generator
114 ... Magnetic head characteristic evaluation device
115 ... Displacement detector
116 ... Phase detector
117 ... Synchronous detector
118: Amplitude / DC voltage converter
119 ... feedback circuit
120: scanning piezoelectric element
201: Head magnetic field frequency dependence
202: Head current frequency dependency
203: Head magnetic field frequency dependency (head part)
401 ... P1 magnetic pole
402 ... P2 magnetic pole
403… Gap center
404: Magnetic pole edge
501: Graph of head magnetic field frequency dependence
502: Graph of head current frequency dependence
601: Graph of head magnetic field frequency dependency (head portion)
701: Graph obtained by multiplying each frequency characteristic of graphs 601 and 502
801: Result when the frequency is 10 MHz
802: Result when the frequency is 350 MHz

Claims (8)

A magnetic recording head measuring device for measuring characteristics of a magnetic recording head,
A probe that scans the surface of the magnetic recording head in a non-contact state,
Vibrating means for vibrating the probe,
A signal generating means for generating an amplitude-modulated signal obtained by amplitude-modulating a carrier, and changing the carrier frequency ,
A head amplifier equivalent circuit having electrical characteristics equivalent to an actual head drive amplifier, generating an amplitude modulation current for operating the magnetic recording head based on the amplitude modulation signal, and applying the current to the magnetic recording head;
Phase displacement measuring means for measuring the phase displacement of the vibration of the probe according to the magnetic field generated from the magnetic recording head,
A magnetic recording head measuring device, comprising: a magnetic field frequency dependency measuring means for measuring a change in the phase displacement with respect to a change in a carrier frequency by the signal generating means as a magnetic field frequency dependency of the magnetic recording head. Current measuring means for measuring the amplitude of an amplitude modulation current applied to the magnetic recording head from the head amplifier equivalent circuit,
2. A current frequency dependency measuring means for measuring a change in the amplitude of the amplitude modulation current with respect to a change in a carrier frequency by the signal generating means as a current frequency dependency of the magnetic recording head. The magnetic recording head measuring device according to the above. Further comprising an amplitude control means for controlling the signal generation means to change the amplitude of the amplitude modulation signal so that the amplitude of the amplitude modulation current is equal to a reference value,
2. The magnetic recording head according to claim 1, wherein the magnetic field frequency dependency measuring means measures a change in the phase displacement with respect to a change in a carrier frequency caused by the signal generating means as a magnetic field frequency dependency of the magnetic recording head. measuring device. A magnetic recording head measuring device for measuring characteristics of a magnetic recording head,
A head amplifier equivalent circuit having electrical characteristics equivalent to that of an actual head drive amplifier , a signal generator, and a current amplitude measuring device, and the signal is supplied to the head amplifier equivalent circuit to which the magnetic recording head is connected. Current frequency dependency measurement for inputting a signal whose signal frequency is changed while maintaining the amplitude at a constant value from a generator and measuring the amplitude of the current supplied to the magnetic recording head using the current amplitude measuring device Means,
A probe that scans the surface of the magnetic recording head in a non-contact state,
Vibrating means for vibrating the probe,
A signal generating means for generating an amplitude-modulated signal obtained by amplitude-modulating a carrier , applying the amplitude-modulated signal to the magnetic recording head as an amplitude-modulated current for operating the magnetic recording head, and changing the carrier frequency ,
Phase displacement measuring means for measuring the phase displacement of the vibration of the probe according to the magnetic field generated from the magnetic recording head,
A magnetic recording head measuring device, comprising: a magnetic field frequency dependency measuring means for measuring a change in the phase displacement with respect to a change in a carrier frequency by the signal generating means as a magnetic field frequency dependency of the magnetic recording head. A magnetic recording head measuring method for measuring characteristics of a magnetic recording head,
Scanning the surface of the magnetic recording head in a non-contact state with the probe vibrated;
Generating an amplitude-modulated signal obtained by amplitude-modulating a carrier, and changing the carrier frequency ;
Applying the amplitude modulation signal to a head amplifier equivalent circuit having electrical characteristics equivalent to an actual head drive amplifier,
Generating an amplitude modulation current for operating the magnetic recording head from the head amplifier equivalent circuit and applying the current to the magnetic recording head;
Measuring the phase displacement of the vibration of the probe according to the magnetic field generated from the magnetic recording head,
Measuring the change in the phase displacement with respect to the change in the carrier frequency as the magnetic field frequency dependence of the magnetic recording head. Measuring the amplitude of the amplitude modulation current applied to the magnetic recording head from the head amplifier equivalent circuit;
6. The method according to claim 5, further comprising: measuring a change in the amplitude of the amplitude modulation current with respect to a change in the carrier frequency as a current frequency dependency of the magnetic recording head. Changing the amplitude of the amplitude modulation signal so that the amplitude of the amplitude modulation current is equal to a reference value,
6. The magnetic recording head measuring method according to claim 5, further comprising the step of: measuring a change in phase displacement with respect to a change in the carrier frequency as a magnetic field frequency dependency of the magnetic recording head. A magnetic recording head measuring method for measuring characteristics of a magnetic recording head,
Using a head amplifier equivalent circuit having electric characteristics equivalent to an actual head drive amplifier , a signal generator, and a current amplitude measuring device, the signal generation is performed on the head amplifier equivalent circuit to which the magnetic recording head is connected. Inputting a signal having a changed signal frequency while maintaining the amplitude at a constant value from the device, and measuring the amplitude of the current supplied to the magnetic recording head using the current amplitude measuring device ;
Scanning the surface of the magnetic recording head in a non-contact state with the probe vibrated;
Generating an amplitude-modulated signal obtained by amplitude-modulating the carrier , applying the amplitude-modulated signal to the magnetic recording head as an amplitude-modulated current for operating the magnetic recording head, and changing the carrier frequency ;
Measuring the phase displacement of the vibration of the probe according to the magnetic field generated from the magnetic recording head,
Measuring the change in the phase displacement with respect to the change in the carrier frequency as the magnetic field frequency dependence of the magnetic recording head.

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