Dynamic magnetic information storage or retrieval – Head – Magnetoresistive reproducing head
Reexamination Certificate
2000-03-01
2003-05-20
Ometz, David L. (Department: 2653)
Dynamic magnetic information storage or retrieval
Head
Magnetoresistive reproducing head
C360S313000
Reexamination Certificate
active
06567246
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a magnetoresistive effect element which produces a high level of output to an outside magnetic field in response to a change in a magnetoresistance. The present invention also relates to a magnetoresistance effect type head including the element suitable for high-density magnetic recording and reproduction, and a magnetic recording apparatus such as a hard disk drive including the head, and methods for fabricating the element, the head, and the apparatus.
2. Description of the Related Art
Recently, hard disk drives (HDD) have been rapidly developed to have more high density capability, and significant advances have been made in reproduction magnetic heads for reading magnetization recorded on such a medium. Among other things, a spin valve which is a magnetoresistance effect element (hereinafter referred to as an MR element) utilizing a giant magnetoresistance effect has been thought to increase the sensitivity of current magnetoresistance effect type heads (hereinafter referred to as an MR head) and is being vigorously studied.
The spin valve includes a non-magnetic layer and two ferromagnetic layers. The non-magnetic layer is sandwiched between the two ferromagnetic layers. The magnetization direction of one of the ferromagnetic layers (pinned layer) is pinned by an exchange bias magnetic field of a pinning layer (the ferromagnetic layer and the pinning layer are referred to collectively as an exchange coupling layer). The magnetization direction of the other ferromagnetic layer (free layer) is allowed to move relatively freely in response to an external magnetic field. The electric resistance of the spin valve is changed according to the angle between the magnetization directions of the pinned layer and the free layer.
Journal of Magnetism and Magnetic Materials 93, p. 101, 1991 discloses a spin valve which includes magnetic layers made of Ni—Fe, a non-magnetic layer made of Cu, and a pinning layer made of Fe—Mn. This spin valve has a magnetoresistance change rate (hereinafter referred to as an MR ratio) of approximately 2%. When the pinning layer is made of Fe—Mn, the MR ratio is small and the blocking temperature (temperature at which a magnetization pinning effect of the pinning layer on the pinned layer vanishes) is not sufficiently high. In addition, Fe—Mn has less corrosion resistance. Therefore, other spin valves have been proposed which include a pinning layer made of a variety of material. Among other things, Pt—Mn has good corrosion-resistance and thermal stability. A pinning layer made of an oxide such as NiO and &agr;-Fe
2
O
3
allows the spin valve to have a very high MR ratio of 15% or more.
However, the spin valve including an NiO pinning layer does not have a sufficiently high blocking temperature, so that the NiO spin valve has less thermal stability.
The &agr;-Fe
2
O
3
spin valve has disadvantage such that a pinning effect on the metal magnetic layer is weak. Particularly, when the spin valve has a dual spin valve structure or when a structure such that the &agr;-Fe
2
O
3
layer is provided on the pinned layer, such disadvantage is significant in the &agr;-Fe
2
O
3
layer. The Pt—Mn spin valve has excellent thermal stability, but does not have as high a MR ratio as the NiO or &agr;-Fe
2
O
3
spin valve. Therefore, the thermal stability as exhibited by Pt—Mn and the large MR ratio is exhibited by NiO or &agr;-Fe
2
O
3
have not been achieved in one element.
Moreover, a small total thickness of the metal layers and a higher MR ratio are required for the magnetoresistance effect element.
SUMMARY OF THE INVENTION
According to one aspect of the present invention, a magnetoresistance effect element includes a free layer, in which a magnetization direction thereof is easily rotated in response to an external magnetic field; a first non-magnetic layer; and a first pinned layer provided on a side opposite to the free layer of the first non-magnetic layer, in which a magnetization direction of the first pinned layer is not easily rotated in response to the external magnetic field. At least one of the first pinned layer and the free layer includes a first metal magnetic film contacting the first non-magnetic layer, and a first oxide magnetic film.
In one embodiment of this invention, the first pinned layer includes the first metal magnetic film and the first oxide magnetic film.
In one embodiment of this invention, the magnetoresistance effect element further includes a second non-magnetic layer provided on a side opposite to the first non-magnetic layer of the free layer; and a second pinned layer provided on a side opposite to the free layer of the second non-magnetic layer, in which a magnetization direction of the second pinned layer is not easily rotated in response to the external magnetic field.
In one embodiment of this invention, the free layer includes the first metal magnetic film and the first oxide magnetic film.
In one embodiment of this invention, a magnetoresistive effect element includes an oxide non-magnetic film provided on a side opposite to the first non-magnetic layer of the free layer, having satisfactory flatness.
In one embodiment of this invention, a magnetoresistance effect element further includes a pinning layer magnetically coupled to the first oxide magnetic film.
In one embodiment of this invention, the free layer further includes a second metal magnetic film provided on a side opposite to the first metal magnetic film of the first oxide magnetic film.
In one embodiment of this invention, a magnetoresistance effect element includes a pinning layer magnetically coupled to the first pinned layer.
In one embodiment of this invention, the first pinned layer further includes a second metal magnetic film provided on a side opposite to the first metal magnetic film of the first oxide magnetic film.
In one embodiment of this invention, the first pinned layer further includes a second metal magnetic film provided on a side opposite to the first metal magnetic film of the first oxide magnetic film; a third metal magnetic film; and an exchange-coupling non-magnetic film antiferromagnetically exchange-coupling the second and third metal magnetic films.
In one embodiment of this invention, the first pinned layer further includes a non-magnetic film provided on a side opposite to the first metal magnetic film of the first oxide magnetic film; and a second oxide magnetic film magnetically exchange-coupling the first oxide magnetic film via the non-magnetic films.
In one embodiment of this invention, the first oxide magnetic film contains Fe element.
In one embodiment of this invention, the first oxide magnetic film contains Fe and X element where X is at least one element selected from Al, Si, B, and N.
In one embodiment of this invention, the first oxide magnetic film contains MFe
2
O
4
as a major component where M is at least one element selected from Fe, Co, and Ni.
In one embodiment of this invention, the first oxide magnetic film contains Fe
3
O
4
as a major component.
In one embodiment of this invention, the first oxide magnetic film contains CoFe
2
O
4
as a major component. p In one embodiment of this invention, the pinning layer contains P—Mn where P is at least one element selected from Pt, Ni, Pd, Ir, Rh, Ru, and Cr.
In one embodiment of this invention, the pinning layer contains &agr;-Fe
2
O
3
or NiO or both, or includes an &agr;-Fe
2
O
3
film and a NiO film.
In one embodiment of this invention, the pinning layer includes an (AB)
2
O
x
layer where a ratio of the combination of element A and element B to oxygen is equal to 2:x; 2.8<x<32; and where t is defined as:
t=
(
Ra+Ro
)/(2·(
Rb+Ro
))
(where Ra, Rb, and Ro denote the ion radii of the atoms A, B, and O, respectively)
and t satisfies 0.8<t<0.97.
In one embodiment of this invention, element B of the (AB)
z
O
x
layer includes at least one transition metal, and has Fe as a major component.
In one embodiment of this invention, element A of the (AB)
a
O
x
layer inclu
Hiramoto Masayoshi
Kawawake Yasuhiro
Matsukawa Nozomu
Sakakima Hiroshi
Satomi Mitsuo
Castro Angel
Matsushita Electric - Industrial Co., Ltd.
Ometz David L.
Renner Otto Boisselle & Sklar
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