Stock material or miscellaneous articles – Composite – Of inorganic material
Reexamination Certificate
1998-10-13
2001-04-03
Kiliman, Leszek (Department: 1773)
Stock material or miscellaneous articles
Composite
Of inorganic material
C423S629000, C423S629000, C423S629000, C423S594120, C360S112000, C324S252000
Reexamination Certificate
active
06210818
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a “spin-valve type” thin film element, in which the electric resistance varies as a function between the magnetization orientation of a pinned magnetic layer and that of a free magnetic layer, which is free to rotate with an applied magnetic field. The invention further relates to improvement of a magnetic material used as the aforementioned pinned magnetic layer.
2. Description of the Related Art
A spin-valve type thin film element is a kind of giant magnetoresistive (GMR) elements utilizing the giant magnetoresistance effect for detecting a recording magnetic field recorded in a recording medium such as a hard disk.
Such a spin-valve type thin film element is composed of at least four layers, i.e., a free magnetic layer, a nonmagnetic electrically conductive layer, a pinned magnetic layer and an antiferromagnetic layer laminated in this order on a suitable substrate, and pairs of a hard magnetic bias layer and an electric conductive layer are laminated on both sides of the four layers.
In general, the conventional spin-valve type thin film element comprises the antiferromagnetic layer composed of an FeMn (iron-manganese) alloy film or a NiMn (nickel-manganese) alloy film, the pinned magnetic layer and free magnetic layer each composed of a NiFe (nickel-iron) alloy film, the nonmagnetic electrically conductive layer composed of a Cu (copper) film, and the hard magnetic bias layer composed of a Co—Pt (cobalt-platinum) alloy film.
The pinned magnetic layer is formed adjacent to the antiferromagnetic layer. The magnetization of the pinned magnetic layer is put into a single domain state in a height direction (the direction of a leakage magnetic filed leaked from a recording medium) and fixed by forming the pinned magnetic layer in a magnetic filed when the antiferromagnetic layer is composed of an FeMn alloy film, or by annealing it when the antiferromagnetic layer is composed of a NiMn alloy film.
The magnetization orientation of the free magnetic layer is aligned with a track width direction by a bias magnetic field from the hard magnetic bias layer, and the magnetization orientations of the free magnetic layer and the pinned magnetic layer are at an angle of 90° with respect to each other.
In a spin-valve type thin film element, a sensing current is fed from the electric conductive layer to the pinned magnetic layer, nonmagnetic electrically conductive layer and free magnetic layer. When a leakage magnetic field is applied from a recording medium to the element, the magnetization orientation (magnetization direction) of the free magnetic layer rotates from the track width direction to the leakage magnetic field direction (height direction). The electric resistance changes as a function between the variation of the magnetization orientation in the free magnetic layer and the fixed magnetization orientation of the pinned magnetic layer, and consequently the voltage changes according to variation of the electric resistance so as to detect the leakage magnetic filed from the recording medium.
Meanwhile, a large exchange anisotropic magnetic field generated in a boundary face between the pinned magnetic layer and the antiferromagnetic layer is preferred. This is because such a large exchange anisotropic magnetic field can satisfactorily put and fix the magnetization of the pinned magnetic layer into a single domain state in a height direction (leakage magnetic field direction from a recording medium).
To provide a large exchange anisotropic magnetic filed, various inventions and publications have been made in which materials of the antiferromagnetic layer and/or pinned magnetic layer are changed or conditions of a heat treatment to generate an exchange anisotropic magnetic filed are suitably adjusted.
It is, however, not only an exchange anisotropic magnetic filed that affects the magnitude of the magnetization. A magnetic filed generated by a magnetoelastic effect also affects the magnitude of the magnetization of pinned magnetic layer. Such a magnetic filed can be determined by a stress and magnetostriction applied to the pinned magnetic layer.
A spin-valve type thin film element has upper, bottom and height side surfaces covered with an insulation film (gap film) composed of, for example, Al
2
O
3
, and an opposite surface to the height side (i.e., an Air Bearing surface (ABS) side; front surface) exposed to the outside. Since the spin-valve type thin film element is composed of a multilayered structure comprising metal films, its coefficient of thermal expansion is larger than that of the insulation film covering the element. Accordingly, a tensile stress directed to the height direction acts upon the spin-valve type thin film element.
When the pinned magnetic layer constituting the spin-valve type thin film element has a negative magnetostriction under the above mentioned condition, the magnetization of the pinned magnetic layer is induced in the track width direction by the magnetoelastic effect.
To be more specific, even if a large exchange anisotropic magnetic filed can be obtained which can satisfactorily put the magnetization of the pinned magnetic layer into a single domain state in the height direction, when a magnetic filed as a function of the magnetoelastic effect acts for orienting the magnetization of the pinned magnetic layer in the track width direction, the magnetization of the pinned magnetic layer is not rigidly fixed in the height direction. Therefore, reproducing characteristics are deteriorated, including an increasing incidence of Barkhausen noises.
SUMMARY OF THE INVENTION
The present invention has been achieved to solve the above-mentioned problems of the prior art. It is, therefore, a principle object of the present invention to provide a spin-valve type thin film element in which the magnetization of a pinned magnetic layer can be induced and firmly fixed in a height direction by a magnetic field as a function of the magnetoelastic effect as well as by an exchange anisotropic magnetic filed.
The present invention provides a spin-valve type thin film element comprising an antiferromagnetic layer, a pinned magnetic layer being formed adjacent to the antiferromagnetic layer and having a magnetization orientation fixed or pinned by an exchange anisotropic magnetic field with respect to the antiferromagnetic layer, and a free magnetic layer formed over and/or under the pinned magnetic layer with the interposition of a nonmagnetic electrically conductive layer, wherein the element further comprises a bias magnetic layer for aligning the magnetization orientation of the free magnetic layer with a direction crossing the magnetization orientation of the pinned magnetic layer, and an electric conductive layer for feeding a sensing current to the pinned magnetic layer, the nonmagnetic electrically conductive layer and the free magnetic layer, the pinned magnetic layer is composed of a CoFe alloy, and the pinned magnetic layer has a positive saturated magnetostrictive constant and had a face central cubic structure (hereinafter referred to as “fcc structure”) at least as a part of its crystal structure.
The CoFe alloy used as the pinned magnetic layer may have a composition formula represented by Co
a
Fe
100−a
, and the composition ratio “a” may preferably be 30≦a≦80, and more preferably be 50≦a≦70 in terms of atomic percent.
The pinned magnetic layer according to the present invention may further includes Ni. In this case, the composition formula of the CoFeNi alloy can be represented by Co
a
Fe
b
Ni
c
, and preferably, in terms of atomic percent, 0≦a≦80, 20≦b≦70 and 0≦c≦80, and more preferably 50≦a≦80, 20≦b≦50 and 0≦c≦30.
When the three segments of a ternary diagram of the aforementioned composition Co
a
Fe
b
Ni
c
are determined as the composition ratios of the elements Co, Fe and Ni respectively, the composition ratios a, b and c (atomic percent) may preferably fall in the range surrounded by the following four points.
Alps Electric Co. ,Ltd.
Brinks Hofer Gilson & Lione
Kiliman Leszek
LandOfFree
Magnetoresistive element does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Magnetoresistive element, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Magnetoresistive element will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2491640