Electricity: measuring and testing – Magnetic – Magnetic information storage element testing
Reexamination Certificate
2002-02-05
2003-09-09
Le, N. (Department: 2862)
Electricity: measuring and testing
Magnetic
Magnetic information storage element testing
C324S244000, C073S105000
Reexamination Certificate
active
06617848
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2001-028551, filed Feb. 5, 2001, the entire contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a magnetic head measuring apparatus for measuring magnetic field characteristics of a magnetic head and a measuring method applied to the magnetic head measuring apparatus.
2. Description of the Related Art
Conventionally, in the process of manufacturing a magnetic head used for, e.g., a hard disk drive, a process of measuring magnetic field characteristics such as field distribution or field saturation phenomenon of a recording head (write head) included in the magnetic head is indispensable. A recording head is formed from, e.g., an inductive thin-film head and has a magnetic gap for generating a recording field corresponding to a signal current applied to the coil.
As the measurement schemes in the measuring process, (1) a scheme using a measuring apparatus called a spin stand dedicated to a head/disk, (2) a scheme using a dedicated magnetic head measuring apparatus using a magnetic force microscope (MFM), and (3) a scheme using computer simulation are known.
In the measuring scheme using a spin stand, a signal for measurement is recorded on a disk recording medium while changing a write current value for a recording head to be measured, and the recorded signal is reproduced by a reproduction head (read head). With the spin stand, magnetic field characteristics of the recording head is measured using the recorded signal output from the reproduction head.
In the measuring scheme using an MFM, a DC (Direct Current) is applied to the recording head, and a DC magnetic field (recorded magnetic field) generated from the recording head is measured by the MFM.
In the scheme using computer simulation, a DC magnetic field (recorded magnetic field) generated from the recording head when a DC (Direct Current) is applied to the recording head is obtained by simulation on a computer.
The various kinds of conventional measuring schemes described above have the following problems.
In the measuring scheme using a spin stand, since a recorded signal is measured through a disk recording medium and reproduction head (MR head), a measurement result including the characteristics of these components is obtained. For this reason, the saturation magnetic field of the recording head cannot be directly observed. In addition, a saturation phenomenon is assumed to occur from a corner (edge) of a magnetic pole of a recording head. However, with this measuring scheme, this phenomenon cannot be locally detected.
In the measuring scheme using an MFM, since a saturation field is measured by supplying only a DC, an improvement of resolving power cannot be expected. When a current value of DC is increased, a very large magnetic field is generated from a recording head. For this reason, an interaction between a probe used in the MFM and a recording field from the recording head ranges not only to the distal end portion of the probe but also to the rear surface portion of the probe. Additionally, since the interaction at the rear surface portion of the probe includes a magnetic field from the neighborhood of the probe, the interactive effect at the rear surface portion of the probe becomes very large. Hence, contribution from the distal end portion of the probe relatively decreases, resulting in a decrease in resolving power.
Furthermore, in the computer simulation, the actual field distribution of a recording head cannot be measured.
BRIEF SUMMARY OF THE INVENTION
The present invention provides a magnetic head measuring apparatus capable of realizing direct observation of a saturation field as magnetic field characteristics of a recording head at a high resolving power and consequently improving recording head measurement performance, and a measuring method applied to the magnetic head measuring apparatus.
According to one aspect of the present invention, there is provided a magnetic head measuring apparatus for executing measurement with respect to at least one measurement point on a recording head, comprising: a probe having a magnetic substance; a vibrator configured to vibrate the probe above the at least one measurement point; a first signal generator configured to supply a drive signal to the vibrator; a second signal generator configured to supply a current containing a direct current (DC) and an alternate current (AC) to the recording head to generate a magnetic field from the recording head; a detector configured to detect a signal corresponding to a force interaction that acts on the probe due to the magnetic field generated from the recording head in accordance with the current supplied by the second signal generator; and a measurement unit configured to measure current dependence of the magnetic field of the recording head from the signal detected by the detector.
According to another aspect of the present invention, there is provided a measuring method applied to a magnetic head measuring apparatus for executing measurement with respect to at least one measurement point on a recording head, the method comprising: supplying a current containing a direct current (DC) and a alternate current (AC) to the recording head to generate a magnetic field from the recording head; bringing a probe having a magnetic substance close to the recording head while vibrating the probe; detecting a signal corresponding to a force interaction that acts on the probe due to the magnetic field generated from the recording head; and measuring current dependence of the magnetic field of the recording head from the detected signal.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.
REFERENCES:
patent: 5440121 (1995-08-01), Yasutake et al.
patent: 5623205 (1997-04-01), Tomita et al.
patent: 5652377 (1997-07-01), Yagi
patent: 6437562 (2002-08-01), Abe
D. Rugar, et al., “Magnetic Force Microscopy: General Principles and Application to Longitudinal Recording Media”, J. Appl. Phys. 68(3), Aug. 1990, pp. 1169-1183.
Aurora Reena
Kabushiki Kaisha Toshiba
Le N.
Pillsbury & Winthrop LLP
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