US 5,844,755 AGranted

Giant magnetoresistive information recording medium, and associated recording and reproducing method and apparatus

AssigneeOki Electric Industry Co., Ltd.

InventorsHaruki Yamane, Yoshinori Maeno, Masanobu Kobayashi

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Abstract

Information is recorded by applying weak and strong magnetic fields to a giant magnetoresistive medium having a pair of ferromagnetic layers, a nonmagnetic interlayer, and an antiferromagnetic layer. The medium preferably has a magnesium-oxide base layer, and may also have an electrode layer. The weak magnetic field magnetizes the ferromagnetic layers in the antiparallel state. The strong magnetic field magnetizes the ferromagnetic layers in the parallel state, which has lower electrical resistance than the antiparallel state. The recorded information is reproduced by detecting the electrical resistance of the medium, either between two electrodes contacting the surface of the medium, or between the electrode layer in the medium and an electrode contacting the surface of the medium.

Claims34

Dependent claims

A giant magnetoresistive information recording medium, comprising:

a pair of ferromagnetic layers, consisting of a first ferromagnetic layer and a second ferromagnetic layer, said pair of ferromagnetic layers representing one information value when magnetized in a mutually parallel state and another information value when magnetized in a mutually antiparallel state, and having a lower electrical resistance in said mutually parallel state than in said mutually antiparallel state;
a nonmagnetic interlayer disposed between said pair of ferromagnetic layers, for preventing exchange coupling between said ferromagnetic layers;
and
an antiferromagnetic layer magnetized in a fixed orientation and disposed adjacent said second ferromagnetic layer, for biasing said second ferromagnetic layer by exchange coupling, so that said second ferromagnetic layer is more easily magnetized parallel to said fixed orientation, and less easily magnetized antiparallel to said fixed orientation, than is said first ferromagnetic layer;
wherein said first ferromagnetic layer, said nonmagnetic interlayer, said second ferromagnetic layer, and said antiferromagnetic layer are formed as a continuous multilayer, in which information can be recorded at any location, and wherein when recorded a plurality of information values are recorded in said continuous multilayer.

2 more elements

A method of recording and reproducing information in a medium having a first ferromagnetic layer, a second ferromagnetic layer, a nonmagnetic interlayer, and an antiferromagnetic layer formed as a continuous multilayer such that a plurality of information values can be recorded in said medium, said plurality of information values comprising a first information value and a second information value, the method comprising the steps of:

applying a first magnetic field to a selected first region of said medium such that said pair of ferromagnetic layers are magnetized in a mutually antiparallel state representing said first information value, said first information value thereby being recorded in said first region;
applying a second magnetic field, stronger than said first magnetic field, to a selected second region of said medium such that said pair of ferromagnetic layers are magnetized in a mutually parallel state representing said second information value, said second information value thereby being recorded in said second region such that both said first and second information values are recorded in said medium;
and
reproducing said first and second information values thus recorded in said medium by detecting electrical resistance of said first and second regions.

1 more element

Dependencies are inferred from the claim text.