Dynamic magnetic information storage or retrieval – Head – Magnetoresistive reproducing head
Reexamination Certificate
2000-10-11
2004-05-18
Klimowicz, William (Department: 2652)
Dynamic magnetic information storage or retrieval
Head
Magnetoresistive reproducing head
C360S319000
Reexamination Certificate
active
06738234
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a thin film magnetic head and a magnetic transducer for use in the same. More particularly, the invention relates to a thin film magnetic head and a magnetic transducer which can obtain resistance properties adaptable to ultra-high-density recording.
2. Description of the Related Art
Recently, an improvement in performance of a thin film magnetic head has been sought in accordance with an increase in a surface recording density of a hard disk or the like. A composite thin film magnetic head, which has a stacked structure comprising a reproducing head having a magnetoresistive element (hereinafter referred to as an MR element) that is a type of magnetic transducer and a recording head having an inductive magnetic transducer, is widely used as the thin film magnetic head.
MR elements include an element using a magnetic film (an AMR film) exhibiting an anisotropic magnetoresistive effect (an AMR effect), and an element using a magnetic film (a GMR film) exhibiting a giant magnetoresistive effect (a GMR effect). The GMR film is mainly used in the MR element for the reproducing head whose surface recording density exceeds 3 Gbit/inch
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. As the GMR film, a “multilayered type (antiferromagnetic type)” film, an “inductive ferromagnetic type” film, a “granular type” film, a “spin valve type” film and the like are proposed. Of these types of films, the spin valve type GMR film is used for the industrialization of a magnetic head.
The spin valve type GMR film has a stacked structure comprising; a magnetic layer having the fixed orientation of magnetization; and a magnetic layer having the orientation of magnetization changing in accordance with a signal magnetic field, in which the magnetic layers are stacked with the nonmagnetic layer in between. Electrical resistance changes in accordance with a relative angle between the orientations of magnetizations of the two magnetic layers. The spin valve type GMR film obtains the rate of resistance change of 2% to 6% (U.S. Pat. No. 5,408,377).
Moreover, a “tunnel junction type” GMR film utilizing a tunnel current passing through a thin insulating layer has been recently developed (U.S. Pat. No. 5,901,018). The tunnel junction type GMR film has a structure in which an insulating layer is sandwiched between two magnetic layers. During the passage of the tunnel current through the insulating layer, electrical resistance changes in accordance with the signal magnetic field. The tunnel junction type GMR film obtains electrical resistance so high that a junction area becomes small. However, shot noise is caused and thus the S/N (signal to noise) ratio becomes low. Consequently, the tunnel junction type GMR film has the limitations of improvement in properties of the magnetic head.
Therefore, attention has been recently paid to an MR element having the so-called CPP (Current Perpendicular to the Plane) structure in which a current is passed through the multilayered type GMR film in the direction of stack (Japanese Unexamined Patent Application Publication No. Hei 5-275769). The multilayered type GMR film has a stack comprising magnetic layers stacked alternately with nonmagnetic layers. The orientations of magnetizations of the magnetic layers change in accordance with the signal magnetic field, and thus electrical resistance changes. The above-mentioned multilayered type GMR film is disclosed in, for example, Japanese Unexamined Patent Application Publication No. Hei 4-360009, Japanese Patent No. 2610376, Japanese Unexamined Patent Application Publication No. Hei 5-90026, Japanese Unexamined Patent Application Publication No. Hei 7-78316 and Japanese Unexamined Patent Application Publication No. Hei 9-180135. According to the multilayered type GMR film, the rate of resistance change is about 1% to 10% when the current is passed perpendicularly to the direction of stacking (Japanese Unexamined Patent Application Publication No. Hei 5-90026). The rate of resistance change is about 10% to 15% when the current is passed in the direction of stacking.
However, currently, demand for high-density recording on the hard disk or the like is increasingly growing. Thus, the surface recording density exceeding 100 Gbit/inch
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is required. A size of the MR element must be about 0.1 &mgr;m in order to meet the demand for such ultra-high-density recording. It is thus necessary to ensure higher head output. A still higher rate of resistance change is therefore needed. Consequently, there is a problem that the heretofore-reported rate of resistance change of 10% to 15% of the CPP structure is insufficient.
In the case of the CPP structure, the rate of resistance change and resistance can be increased as the number of magnetic layers is increased. However, when the number of magnetic layers is increased and thus a thickness of the stack along the direction of stacking is increased, a length of a surface facing a recording surface increases in the direction of thickness of the stack. Thus, there is a problem of inadaptability to high-density recording.
SUMMARY OF THE INVENTION
It is an object of the invention to provide a thin film magnetic head and a magnetic transducer, which have resistance properties adaptable to ultra-high-density recording.
A thin film magnetic head of the invention comprises a stack including a plurality of magnetic layers stacked alternately with a plurality of nonmagnetic layers, the stack having a projecting portion projecting toward a magnetic medium.
In a thin film magnetic head of the invention, a signal magnetic field of the magnetic medium is captured by the projecting portion of the stack. Therefore, the number of magnetic layers of the stack can be increased without increasing a length (sometimes called a magnetic gap length) of a signal magnetic field capturing surface along the direction of stacking of the stack. Accordingly, the rate of resistance change and resistance can be increased.
In a thin film magnetic head of the invention, it is preferable that a length of the projecting portion along the projecting direction thereof is 0.1 &mgr;m or less. Preferably, a thin film magnetic head further comprises a current path for passing a current through the stack in the direction of stacking. Preferably, a pair of shield layers and a pair of gap layers for sandwiching the stack therebetween function as the current path. Preferably, the stack has an edge face facing the magnetic medium, and at least one of the shield layers has a magnetic field capture limiting portion for partially limiting an effect of a signal magnetic field on the stack through the edge face. Preferably, the stack has a part facing a magnetic medium, and at least one of the shield layers has a magnetic field capture limiting portion provided in an area corresponding to the part of the stack.
Preferably, at least one of the magnetic layers is made of a material containing at least Co in a group including Co (cobalt), Fe (iron) and Ni (nickel), or a material containing at least Ni in a group including Ni, Co, Fe, Cr (chromium), Ta (tantalum), Rh (rhodium), Mo (molybdenum), Zr (zirconium) and Nb (niobium). Preferably, at least one of the magnetic layers includes a nickel-containing layer made of a material containing at least Ni in a group including Ni, Co, Fe, Cr, Ta, Rh, Mo, Zr and Nb, and a cobalt-containing layer made of a material containing at least Co in a group including Co, Fe and Ni.
Preferably, a thickness of each of the magnetic layers is from 1 nm to 6 nm inclusive. Preferably, the number of the magnetic layers is from 2 to 20 inclusive. Preferably, at least one of the nonmagnetic layers is made of a material containing at least one element in a group consisting of Au (gold), Ag (silver), Cu (copper), Ru (ruthenium), Rh, Re (rhenium), Pt (platinum) and W (tungsten). Preferably, at least one of the nonmagnetic layers is made of a material containing Ni and Cr. Preferably, one of the nonmagnetic layers, which is located on one outermost side in the direction of stacking, is made of
Araki Satoru
Shimazawa Koji
Klimowicz William
Oliff & Berridg,e PLC
TDK Corporation
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