Dynamic magnetic information storage or retrieval – Head – Magnetoresistive reproducing head
Reexamination Certificate
2000-05-31
2003-09-23
Davis, David (Department: 2652)
Dynamic magnetic information storage or retrieval
Head
Magnetoresistive reproducing head
Reexamination Certificate
active
06624987
ABSTRACT:
TECHNICAL FIELD
This invention relates to a magnetic device including a magnetoresistive element such as a magnetic head for recording an information signal on and/or reading/reproducing an information signal from a magnetic medium, a method for manufacturing such a head and a magnetic recording apparatus using such a head.
This application is based on Japanese Patent Application No. Hei 11-1153051, the contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
Various documents disclose a transducer for the magnetic data reading called a magnetoresistive sensor (hereinafter referred to as “MR sensor”) or head, and it has been known that such a sensor can read data from a magnetized surface at a high linear density. The MR sensor detects a magnetic field signal through a change in resistance which is sensed by a read element as a function of the strength and direction of the magnetic flux. This type of conventional MR sensor operates based on the anisotropic magnetoresistive effect (hereinafter referred to as “AMR effect”) in which one component of the resistance of the read element changes in proportion to the square of the cosine of the angle between the direction of magnetization and the direction of the sense current flowing through the element. The AMR effect is described in detail by D. A. Thompson et al. in the article “Memory, Storage and Related Applications”, IEEE Trans. on Mag. MAG-11, page 1039 (1975). In magnetic heads utilizing the AMR effect, a longitudinal bias is often applied to suppress Barkhausen noise wherein an antiferromagnetic material such as FeMn, NiMn and nickel oxide is used as the longitudinal biasing material.
Recently, some documents have described a more remarkable magnetoresistive effect in which the change in resistance in a laminated magnetic sensor is caused by a spin-dependent transmission of conduction electrons between magnetic layers through a nonmagnetic layer and the accompanying spin-dependent scattering at the interface of the layers. This magnetoresistive effect is called by various names such as “giant magnetoresistive effect” and “spin-valve effect”. This type of magnetoresistive sensor is made of appropriate materials and has an improved sensitivity and a larger resistance change as compared to those observed in a sensor utilizing the AMR effect. In an MR sensor of this type, the resistance in a plane between a pair of ferromagnetic layers separated by a nonmagnetic layer changes in proportion to the cosine of the angles between the directions of magnetization of the two layers.
Japanese Unexamined Patent Application, First Publication No. Hei. 2-61572 which claims a priority of June 1988 discloses a laminated magnetic structure which can provide a large MR change caused by an antiparallel alignment of magnetizations in the magnetic layers. The specification of this publication refers to ferromagnetic transition metals and alloys as materials which can be used in the laminated structure. It also discloses a structure in which a pinning layer is added to at least one of the two ferromagnetic layers separated by an intermediate layer, and the fact that FeMn is suitable for the pinning layer.
Japanese Unexamined Patent Application, First Publication No. Hei. 4-103014 filed on Aug. 22, 1990, describes a ferromagnetic tunnel junction film which takes the form of a multilayer film having an intermediate layer inserted between ferromagnetic layers, wherein a biasing magnetic field from an antiferromagnetic material is applied to at least one of the ferromagnetic layers.
Japanese Unexamined Patent Application, First Publication No. Hei 10- 162327 which claims a priority of Nov. 27, 1996 describes about an example of reproducing heads with a ferromagnetic tunnel junction film which has such a structure that a layer (longitudinal biasing layer) for controlling magnetic domains in the free layer does not contact the free layer, wherein a film of a material other than the metallic materials constituting the ferromagnetic tunnel junction film is formed.
There has been proposed a shield type magnetoresistive effect element utilizing a ferromagnetic tunnel junction film which has such a structure that the longitudinal biasing layer is prevented from directly contacting the ferromagnetic tunnel junction film by means of an insulating material such as alumina (see Japanese Unexamined Patent Application, First Publication No. Hei 10-162327). This is to solve the problem that, although in the case of a shield type element with a ferromagnetic tunnel junction a sense current should flow through the tunnel junction portion perpendicularly thereto, with a structure similar to that of the conventional shield type element utilizing a spin valve a sense current bypasses the barrier layer and flows through the longitudinal biasing portion which is located near the barrier layer and has lower resistance value than that of the barrier layer, as a result of which the sense current does not contribute to the detection of the resistance change. However, since this structure is attained by means of a process of further forming a film of alumina upon end portions of the ferromagnetic tunnel junction film formed by patterning in advance, during the patterning process of the ferromagnetic tunnel junction film, metal is scattered when patterning those of the layers constituting the ferromagnetic tunnel junction film which are disposed below the barrier layer, and the scattered metal is redeposited on side walls of those layers including the barrier layers which have already been patterned. Consequently, the sense current bypasses the barrier layer and flows through the redeposited layer in the finished element, causing the MR ratio to be significantly reduced.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a magnetoresistive effect element which is easy to manufacture and in which the sense current is prevented from bypassing the barrier layer.
It is another object of the invention to provide a method for manufacturing such a magnetoresistive effect element.
It is a further object of the invention to provide an apparatus which uses such a magnetoresistive effect element.
In the first aspect of the present invention, a magnetoresistive effect element comprising: a ferromagnetic tunnel junction film which comprises, for forming a basic structure thereof, an arrangement of a free layer, a barrier layer formed on the free layer and a pinned layer formed on the barrier layer or an arrangement of a pinned layer, a barrier layer formed on the last-mentioned pinned layer and a free layer formed on the last-mentioned barrier layer, wherein pattern of the ferromagnetic tunnel junction film comprises an oxide or a nitride of a metallic material constituting the ferromagnetic tunnel junction film.
In the second aspect of the invention, a magnetoresistive effect element comprising: a ferromagnetic tunnel junction film which comprises, for forming a basic structure thereof, an arrangement of a free layer, a barrier layer formed on the free layer, a pinned layer formed on the barrier layer and a pinning layer formed on the pinned layer or an arrangement of a pinning layer, a pinned layer formed on the last-mentioned pinning layer, a barrier layer formed on the last-mentioned pinned layer and a free layer formed on the last-mentioned barrier layer, wherein a pattern of the ferromagnetic tunnel junction film comprises an oxide or a nitride of a metallic material constituting the ferromagnetic tunnel junction film.
In the third aspect of the invention, a magnetoresistive effect element comprising: a ferromagnetic tunnel junction film which comprises, for forming a basic structure thereof, an arrangement of an underlayer, a free layer formed on the underlayer, a barrier layer formed on the free layer, a pinned layer formed on the barrier layer and a pinning layer formed on the pinned layer or an arrangement of an underlayer, a pinning layer formed on the last-mentioned underlayer, a pinned layer formed on the last-ment
Fukami Eizo
Hayashi Kazuhiko
Honjou Hiroaki
Ishiwata Nobuyuki
Nagahara Kiyokazu
Davis David
NEC Corporation
Young & Thompson
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