Dynamic magnetic information storage or retrieval – Head – Magnetoresistive reproducing head
Reexamination Certificate
2000-02-23
2003-10-21
Korzuch, William (Department: 2651)
Dynamic magnetic information storage or retrieval
Head
Magnetoresistive reproducing head
Reexamination Certificate
active
06636394
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention concerns a magnetic resistance type sensor used in a magnetic recording device, and specifically concerns a magnetic sensor and thin-film magnetic head which utilize the spin-valve magnetic resistance effect.
2. Background Information
Recently, magnetic resistance (MR) sensors consisting of a spin-valve film with a sandwich structure in which a pair of magnetic layers are laminated on a substrate with a non-magnetic layer sandwiched in between have been developed in order to increase the magnetic field sensitivity in playback magnetic heads by reducing the saturation magnetic field. In spin-valve films, the magnetization of one of the magnetic layers (i. e., the pin magnetic layer) is fixed in the direction of height of the element by an exchange-coupling magnetic field with the adjacent antiferromagnetic layer, while the magnetization of the other magnetic layer (i. e., the free magnetic layer) is converted into a single magnetic domain in the direction of the track width of the element, generally by a hard bias method utilizing the magnetic field of a permanent magnet, so that this magnetization can freely be caused to rotate by the external magnetic field.
As the unidirectional isotropic magnetic field created by the antiferromagnetic layer increases in magnitude, the pin magnetic layer can be more favorably converted into a single magnetic domain. Furthermore, as the magnetization of this layer becomes more sufficiently fixed, the linearity of the magnetic response to the external magnetic field is more reliably insured, so that the magnetic characteristics of the magnetic sensor are improved. As is described in for example Japanese Patent Application Kokai No. 9-35212, the characteristics required in the antiferromagnetic material used include the ability to obtain a large exchange-coupling magnetic field, the ability to raise the blocking temperature to a high temperature, superior corrosion resistance, a low heat treatment (annealing) temperature, and the ability to achieve a small film thickness, etc. In the past, various types of materials have been proposed.
Meanwhile, from the standpoints of obtaining a thin magnetic sensor, reducing power consumption and achieving a high recording density, etc., it is desirable that the abovementioned antiferromagnetic layer be made as thin as possible.
However, FeMn alloys, which have generally been used as antiferromagnetic materials in the past, suffer from the problem of susceptibility to corrosion. Furthermore, IrMn alloys, RhMn alloys and FeMn alloys, etc., are easily affected by the underlayer, and especially in the case of so-called bottom type spin-valve structures in which the antiferromagnetic layer is disposed on the substrate side and the pin magnetic layer is laminated on top of this antiferromagnetic layer, it is necessary to install an underlayer film with a high (111) crystal orientation, or to increase the film thickness. Furthermore, in the case of NiMn alloys, it is necessary to perform a heat treatment (annealing) at a high temperature in order to insure sufficient exchange-coupling with the pin magnetic layer. As a result, diffusion of the metal elements in the pin layer
on-magnetic layer/free layer occurs so that there is a danger of lowering the MR ratio.
In the spin-valve type thin-film magnetic head described in Japanese Patent Application Kokai No. 10-91921, the antiferromagnetic layer is formed from a PtMn alloy or PdMn alloy in order to eliminate such problems. According to the gazette of this application, PtMn alloys and PdMn alloys have a good corrosion resistance. Furthermore, these alloys show an effective exchange-coupling magnetic field when heat-treated at a low temperature of 230° C. or lower, and have a high blocking temperature, so that a favorable thin-film magnetic head which is superior in terms of thermal stability is obtained.
However, even in cases where such alloys are used in the antiferromagnetic layer, it is necessary to increase the (111) crystal orientation at the interface with the pin magnetic layer by increasing the film thickness to for example 250 angstroms or greater in order to insure a stable exchange-coupling magnetic field with a sufficient value. If the film thickness of the antiferromagnetic layer is increased to an excessive extent, the shunting of the sensing current into the antiferromagnetic layer increases, so that the problem of a drop in the MR ratio arises. Furthermore, from the standpoints of high recording density and reduction in the size of the magnetic head accompanying a reduction in the size of the overall apparatus, it is desirable to achieve a reduction in the thickness of the magnetic sensor.
SUMMARY OF THE INVENTION
A spin-valve magnetic resistance sensor is disclosed. In one embodiment, the spin-valve magnetic resistance sensor includes a magnetic resistance effect film having a pair of magnetic layers with a non-magnetic layer sandwiched in between. An antiferromagnetic layer is located adjacent to one of the pair of magnetic layers. The magnetic resistance effect film and the antiferromagnetic layer are laminated on a substrate. The antiferromagnetic layer includes an antiferromagnetic material including one of a Pt—Mn—X alloy, an Ir—Mn—X alloy, an Rh—Mn—X alloy, an Ru—Mn—X alloy or a Pd—Mn—X alloy. X is at least one element selected from groups IIa, IVa, Va, IIIb and IVb of a periodic table. The content of X is in a range of 0.1 at % to 15 at %.
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Fukagawa Tomoki
Hikami Fuminori
Nishida Hiroshi
Nose Masateru
Castro Angel
Korzuch William
Read-Rite SMI Corp.
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