Stock material or miscellaneous articles – Composite – Of inorganic material
Reexamination Certificate
1999-12-27
2002-02-19
Kiliman, Leszek (Department: 1773)
Stock material or miscellaneous articles
Composite
Of inorganic material
C428S690000, C428S690000, C428S690000, C428S690000, C428S690000, C428S900000, C360S112000
Reexamination Certificate
active
06348274
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a magnetoresistive element and a magnetic recording apparatus, and more particularly to a magnetoresistive element using a spin valve structure, and a magnetic recording apparatus using the magnetoresistive element as its magnetic head.
In general, reading of information recorded on a magnetic recording medium has been conducted by moving a reproducing magnetic head having a coil relative to the recording medium and detecting a voltage induced in the coil by electromagnetic induction generated upon movement of the magnetic head. It is also known to use a magnetoresistive element (hereinafter called “MR element”) for reading out information (see, for example, IEEE MAG-7, 150(1971). Magnetic heads using a MR element (hereinafter called “MR head”) relies on the phenomenon that electric resistances of some ferromagnetic materials vary with intensity of external magnetic field.
Along with recent progress toward miniaturization and large capacity of magnetic recording mediums, reproduced magnetic signals of information read out from recording mediums are getting weaker and weaker, and MR heads more sensitive and capable of extracting larger outputs are being anticipated. Especially in multi-layered films having a sandwich structure of ferromagnetic
on-magnetic/ferromagnetic layers, large magnetoresistance effects have been obtained. That is, while applying an exchanging bias to one of two ferromagnetic layers interposing a non-magnetic layer between them so as to pin its magnetization, magnetization of the other ferromagnetic layer is reversed by an external magnetic field (signal magnetic field, for example). Thus, the relative angle of magnetized directions of these two ferromagnetic layers sandwiching the non-magnetic layer is change, and a large magnetoresistance effect is obtained. The multi-layered film of this type is called “spin valve structure” (see Phys. Rev. B., Vol. 45, p806 (1992), J. Appl. Phys. Vol. 69, p4774(1991), for example).
Spin valve structures have large magnetoresistance changing rates ranging from 5% to 8% and their magnetization can be changed in low magnetic fields, spin valve structures are suitable for MR elements. However, to cope with higher recording density, larger MR changing rates are needed, and it is desired to increase current MR changing rates to two through three times or more. However, it is difficult to obtain MR changing rates larger than 10% with spin valve structures of a type simply stacking metal layers. Recently, attention has come to be paid to “specular spin valve structures” made by using an insulating ferroelectric material made of oxides such as NiO, Fe
2
O
3
, or the like, as the bias film and stacking an oxide film on the surface of the other magnetic material as well. As to specular spin valve structures, it is known that, by further sandwiching a sandwich film of magnetic
on-magnetic/magnetic layers between insulators, electrons can be specular-reflected at the metal/insulator interface and magnetoresistance effect as large as approximately 20% can be obtained. Specular spin valve structures need sandwiching the magnetic
on-magnetic/magnetic sandwich film with oxide layers from opposite sides thereof, and simultaneously need stacking at least one bias film in contact one of those magnetic layers for pinning magnetization. For this purpose, oxide antiferromagnetic layers of NiO, Fe
2
O
3
, or the like, are currently used. Heretofore, however, no satisfactory oxide antiferromagnetic material having an acceptable bias property has been known, and this is a bar against their practical use. That is, not having insulating antiferromagnetic material having a sufficiently large exchange bias magnetic field and a sufficiently high blocking temperature, it is still difficult to use specular spin valve structures as practical materials.
On the other hand, there is a recently proposed method which inserts a very thin oxide in a magnetic layer to obtain specular effect while using a metal antiferromagnetic material. With this method, a large MR effect can be obtained while using a metal antiferromagnetic material having a large exchange bias magnetic field and a sufficiently high blocking temperature. In this case, however, it is important to make the very thin oxide layer with a high accuracy and to make a good oxide layer while ensuring a high reproducibility.
SUMMARY OF THE INVENTION
It is therefore an object of the invention to provide a MR element and a magnetic recording apparatus using a MR element which has a pinned layer of a good bias property while using a secular spin valve structure with a large MR changing rate, and is improved in soft magnetic property.
To accomplish the object, a first MR element according to the invention, having a spin valve structure which includes a first magnetic film, a second magnetic film, and a non-magnetic spacer film interposed between the first magnetic film and the second magnetic film, is characterized in that: at least one of the first magnetic film and the second magnetic film includes a first ferromagnetic metal layer; a first non-metal layer provided on the first ferromagnetic metal layer; a second non-metal layer provided on the first non-metal layer and different in composition from the first non-metal layer; and a second ferromagnetic metal layer provided on the second non-metal layer. Thereby, a non-metal layer for specular-reflecting electrons can be made very thin with a good reproducibility.
A second magnetoresistive element according to the invention, having a spin valve structure which includes a first magnetic film, a second magnetic film, and a non-magnetic spacer film interposed between said first magnetic film and said second magnetic film, is characterized in that: at least one of said first magnetic film and said second magnetic film includes a first ferromagnetic metal layer; a second ferromagnetic metal layer provided on said first ferromagnetic metal layer and different in composition from said first ferromagnetic metal layer; a non-metal layer provided on said second ferromagnetic metal layer; and a third ferromagnetic metal layer provided on said non-metal layer. Thereby, a non-metal layer for specular-reflecting electrons can be made very thin with a good reproducibility.
A third magnetoresistive element according to the invention, having a spin valve structure which includes a first magnetic film, a second magnetic film, and a non-magnetic spacer film interposed between said first magnetic film and said second magnetic film, is characterized in that: at least one of said first magnetic film and said second magnetic film includes a first ferromagnetic metal layer; a first non-metal layer provided on said first ferromagnetic metal; a second ferromagnetic metal layer provided on said first non-metal layer; a second non-metal layer provided on said second ferromagnetic metal layer; and a third ferromagnetic metal layer provided on said second non-metal layer. Thereby, a specular-reflection of the electrons can be realized in much improved efficiency.
A fourth magnetoresistive element according to the invention, having a spin valve structure which includes a first magnetic film, a second magnetic film, and a non-magnetic spacer film interposed between said first magnetic film and said second magnetic film, is characterized in that: at least one of said first magnetic film and said second magnetic film includes: a first ferromagnetic metal layer containing at least one element selected from the group consisting of lithium (Li), beryllium (Be), sodium (Na), magnesium (Mg), aluminum (Al), silicon (Si), phosphorus (P), potassium (K), calcium (Ca), scandium (Sc), gallium (Ga), rubidium (Rb), strontium (Sr), yttrium (Y), cesium (Cs), barium (Ba) and elements belonging to the lanthanide series by not less than 1%; a non-metal layer formed on said first ferromagnetic metal layer; and a second ferromagnetic metal layer formed on said non-metal layer. Thereby, a non-metal layer for specular-reflecting electrons can be made v
Iwasaki Hitoshi
Kamiguchi Yuzo
Sahashi Masashi
Yuasa Hiromi
LandOfFree
Magnetoresistive element and magnetic recording apparatus 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 and magnetic recording apparatus, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Magnetoresistive element and magnetic recording apparatus will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2973960