Dynamic magnetic information storage or retrieval – Head – Core
Reexamination Certificate
1999-09-02
2002-10-22
Klimowicz, William (Department: 2652)
Dynamic magnetic information storage or retrieval
Head
Core
C360S128000
Reexamination Certificate
active
06469868
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a thin-film magnetic head having at least an induction-type magnetic transducer and a method of manufacturing the thin-film magnetic head.
2. Description of the Related Art
Thin-film magnetic heads have been widely used in hard disk drives used for computers and so on. Composite thin-film magnetic heads in particular have been widely used. A composite thin-film magnetic head is made of a layered structure including a recording head having an induction-type magnetic transducer for writing and a reproducing head having a magnetoresistive (MR) element for reading.
An induction-type magnetic transducer has two magnetic layers and a thin-film coil placed between the magnetic layers. The magnetic layers include magnetic pole portions opposed to each other with a gap layer in between. The pole portions are placed on a side of end faces of the magnetic layers facing toward a recording medium. The magnetic layers are magnetically coupled to each other on the other side.
With an increase in recording density of a hard disk drive used for computers and so on, the maximum frequency of data recorded or reproduced through the use of a thin-film magnetic head has reached a frequency as high as 100 MHz or above. In the case of an extremely high-speed hard disk drive, in particular, the maximum frequency of data to write has reached the order of 200 MHz. If the frequency of data to write increases, eddy current loss increases in the magnetic layers of an induction-type magnetic transducer. Accordingly, the following problems of reductions in properties have arisen: a reduction in intensity of a write magnetic field generated from the pole portions opposed to each other with the gap layer in between; an increase in delay between a write current (a current responsive to data to write) supplied to the coil and generation of a write magnetic field; and a decrease in gradient of rise of a write magnetic field with respect to time.
In order to suppress such eddy current loss, measures have been devised in related art, such as reducing a magnetic path length, that is, the length of the magnetic path made up of the magnetic layers between the medium-facing-surface-side end and the other end, or using a magnetic material with a high resistivity for the magnetic layers.
To reduce the magnetic path length, it is required to reduce the number of turns of the coil or to tightly wind the coil. However, there is a limit to doing so in terms of manufacturing method or performance characteristics.
Even if a magnetic material with a high resistivity is used for the magnetic layers to suppress eddy current loss or a material with a high saturation flux density is used to increase the intensity of a write magnetic field, it is difficult to sufficiently increase the intensity of a write magnetic field or the gradient of rise of a write magnetic field with respect to time when the frequency of data to write increases.
SUMMARY OF THE INVENTION
It is an object of the invention to provide a thin-film magnetic head and a method of manufacturing the same for improving performance characteristics thereof in the case where the frequency of data to write is high, in particular.
A thin-film magnetic head of the invention comprises: two magnetic layers including magnetic pole portions opposed to each other and placed in regions on a side of ends of the magnetic layers facing toward a recording medium, and connecting portions magnetically coupled to each other and placed in regions on a side of the other ends of the magnetic layers, the magnetic layers each being made up of at least one layer; a gap layer provided between the pole portions of the magnetic layers; a thin-film coil placed between the magnetic layers, being insulated from the magnetic layers; and a nonmagnetic conductive member placed to face at least part of at least one of the magnetic layers. In the invention the expression ‘to face at least part of the magnetic layer’ includes the case in which the member faces at least part of the magnetic layer, being in contact with the at least part of the magnetic layer and the case in which the member faces at least part of the magnetic layer with another layer in between.
According to the magnetic head of the invention, eddy currents are induced inside the nonmagnetic conductive member by a write current. The eddy currents suppress a magnetic field leaking from the magnetic layers.
In the magnetic head the nonmagnetic conductive member may be placed to face a portion of at least one of the magnetic layers including the vicinity of the connecting portion.
In the magnetic head the nonmagnetic conductive member may face a surface of the at least one of the magnetic layers opposite to a surface thereof on a side of which the thin-film coil is placed. Alternatively, the nonmagnetic conductive member may face a surface of the at least one of the magnetic layers on a side of which the thin-film coil is placed.
In the magnetic head the nonmagnetic conductive member may be in contact with at least one of the magnetic layers. In this case eddy currents generated inside the magnetic layer are fed to the nonmagnetic conductive member, too. The adverse effects of eddy currents are thereby reduced.
The magnetic head may further comprise an insulating layer placed between the nonmagnetic conductive member and the magnetic layer which the nonmagnetic conductive member faces.
In the magnetic head the resistivity of the nonmagnetic conductive member is preferably lower than that of the magnetic layer which the nonmagnetic conductive member faces.
A method of the invention is provided for manufacturing a thin-film magnetic head comprising: two magnetic layers including magnetic pole portions opposed to each other and placed in regions on a side of ends of the magnetic layers facing toward a recording medium, and connecting portions magnetically coupled to each other and placed in regions on a side of the other ends of the magnetic layers, the magnetic layers each being made up of at least one layer; a gap layer provided between the pole portions of the magnetic layers; and a thin-film coil placed between the magnetic layers, being insulated from the magnetic layers. The method includes: the steps of forming the magnetic layers, the gap layer, and the thin-film coil, respectively; and the step of forming a nonmagnetic conductive member such that the member faces at least part of at least one of the magnetic layers.
In the method of the invention the nonmagnetic conductive member may be placed to face a portion of at least one of the magnetic layers including the vicinity of the connecting portion in the step of forming the nonmagnetic conductive member.
In the method the nonmagnetic conductive member may be placed to face a surface of the at least one of the magnetic layers opposite to a surface thereof on a side of which the thin-film coil is placed in the step of forming the nonmagnetic conductive member. Alternatively, the nonmagnetic conductive member may be placed to face a surface of the at least one of the magnetic layers on a side of which the thin-film coil is placed.
In the method the nonmagnetic conductive member may be brought to contact with at least one of the magnetic layers in the step of forming the nonmagnetic conductive member.
In the method an insulating layer may be further formed between the nonmagnetic conductive member and the magnetic layer which the nonmagnetic conductive member faces.
In the method the resistivity of the nonmagnetic conductive member is preferably lower than that of the magnetic layer which the nonmagnetic conductive member faces.
Other and further objects, features and advantages of the invention will appear more fully from the following description.
REFERENCES:
patent: 4242711 (1980-12-01), Sata et al.
patent: 5313356 (1994-05-01), Ohkubo et al.
patent: 5838521 (1998-11-01), Ravipati
patent: 5949627 (1999-09-01), Williams et al.
patent: 6031696 (2000-02-01), Yamanaka
patent: 6125010 (2000-09-01), Keel et
Takano Ken-ichi
Yamamoto Takahiro
Yamanaka Noboru
Klimowicz William
Oliff & Berridg,e PLC
TDK Corporation
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