Dynamic magnetic information storage or retrieval – Head – Magnetostrictive head
Reexamination Certificate
1999-06-04
2004-09-14
Tianjie, Chen (Department: 2652)
Dynamic magnetic information storage or retrieval
Head
Magnetostrictive head
Reexamination Certificate
active
06791807
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention concerns a spin-valve magnetic transducing element in which, in essence, a free magnetic layer
onmagnetic layer/fixed magnetic layer are formed in layers on a substrate, and the magnetization of the fixed magnetic layer is fixed by an antiferromagnetic layer, as well as a magnetic head equipped with such a spin-valve magnetic transducing element.
2. Background Information
In the past, magnetic transducing elements with a spin-valve film structure have been proposed in order to decrease the saturation magnetic field and raise the magnetic field sensitivity in magnetic heads for reproduction. In general, spin-valve films consist of a sandwich structure in which two opposing magnetic layers enclose a nonmagnetic layer (electrically conductive layer) on a substrate. The magnetization of one of the magnetic layers (the pinned layer) is fixed in the element height direction by an exchange-coupling magnetic field with an antiferromagnetic layer adjacent to it. The magnetization of the other magnetic layer (the free layer) is generally formed into a single magnetic domain in the track width direction of the element by a hard-bias method using the magnetic field of a permanent magnet, and it is free to rotate as the result of an external magnetic field.
Ideally, a spin-valve film should be used in a state in which the magnetization direction of the pinned layer and the magnetization direction of the free layer are perpendicular. When the magnetization of the free layer rotates due to a magnetic field from a recording medium or other outside source, differences in the angle between the magnetization directions of the pinned layer and free layer cause changes in the magnetoresistance of the element, and by this means signals recorded in the recording medium are detected.
As shown in
FIG. 2A
, the spin-valve film
1
is formed in approximately rectangular shape on a wafer; on its left and right sides are formed permanent-magnet films, and on top are formed lead layers
2
a
,
2
b
. In this state, a compressive stress acts on the spin-valve film
1
within its plane from both the X and Y directions. If, in order to cut away individual elements, the aforementioned wafer is cut in an air-bearing surface (ABS) indicated by the imaginary line
3
, the stress at the ABS is released, so that the stress distribution changes; compressive stress acts on the spin-valve film
1
in the X direction and tensile stress acts in the Y direction, as shown in FIG.
2
B.
In general, when the magnetostriction constant is positive, the magnetization of a magnetic film is oriented easily in the direction of action of tension, and when it is negative, the magnetization is oriented easily in the direction of action of compression In the structures of spin-valve films in the past, the magnetostriction constant of the free layer has been set targeting a value of zero, so that the influence of stress would not be felt. However, due to the composition of actual magnetic film materials and for other reasons, it is difficult to make the magnetostriction constant of the free layer exactly zero, and there exists scattering of approximately±3×10
−7
or so. Consequently the effect of stress is not completely eliminated, and there is the problem of the occurrence of scattering in the element sensitivity, so that stability is difficult.
Further, in many spin-valve films a single magnetic domain is induced in the free layer in the element track width direction by means of a hard-bias method in which permanent-magnet films are placed on either side as magnetic domain-controlling layers. In this case, both ends of the pinned layer are affected by the magnetic field of the aforementioned permanent-magnet films, and so there is concern that the magnetization direction may no longer be 90° from the magnetization direction of the free layer. For this reason, there is the problem that at both ends of the spin-valve film the MR ratio changes and sensitivity declines, so that as a whole, uniform sensitivity cannot be obtained in the track width direction.
SUMMARY OF THE INVENTION
A spin-valve magnetic transducing element is disclosed. In one embodiment, the spin-valve magnetic transducing element includes a free magnetic layer having a negative magnetostriction constant, a fixed magnetic layer, a nonmagnetic layer enclosed between the free and fixed magnetic layers and an antiferromagnetic layer adjacent to the fixed magnetic layer, formed in layers on a substrate. Additional features and benefits of the present invention will become apparent from the detailed description, figures and claims set forth below.
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1999 IEEE International Magnetics Conference Digest of Technical Papers, Giant Magnetoresistive (GMR) Sensor Microelectromechanical System (MEMS) Device, Dr. Rajeshuni Ramesham, Ph.D., Apr. 1999, vol. 5 No. 1.
Ando Masahiko
Hikami Fuminori
Kamimura Hirohiko
Komaki Kenji
Lederman Marcos M.
Burgess & Bereznak LLP
Read-Rite SMI Corporation
Tianjie Chen
LandOfFree
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