Antiferromagnetic-ferromagnetic exchange bias films
AssigneeInternational Business Machines Corporation
InventorsRobert Douglas Hempstead, Sol Krongelb, Daniel Andrew Nepela, David Allen Thompson, Erich Philipp Valstyn
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Abstract
In thin film magnetic transducers, e.g., inductive or magnetoresistive recording heads, at least a pair of layers of a ferromagnetic material and an antiferromagnetic material are deposited upon one another and exchange coupled to retain a unidirectional bias in the plane of the ferromagnetic material. When multiple pairs of layers are used, they are separated by layers of nonmagnetic material. In some cases, successive pairs of layers of material with unidirectional bias have their directions of bias pointing in opposite directions. The domain walls in the layers of material are minimized by this technique.
Claims53
A magnetic thin film structure including a sandwich composed of layers including
- a first layer comprising a ferromagnetic material in direct atomic contact with a second layer of an antiferromagnetic material,
- said first layer having a coercivity of less than about 10 Oersteds
- and a unidirectional magnetic bias sustained by an exchange interaction relationship with said second layer provided by alignment of spins in said antiferromagnetic material, and
- an exchange coupling field H.sub.e greater than the coercivity H.sub.c in the presence of said exchange interaction.
A magnetic thin film structure including a sandwich composed of a plurality of layers including
- a first pair of layers including a layer of soft magnetic material in direct contact with a layer of antiferromagnetic material wherein said soft material has a unidirectional soft bias direction sustained by an exchange interaction relationship with said antiferromagnetic material,
- an intermediate layer of a nonmagnetic material,
- a second pair of layers including a second layer of a soft magnetic material in direct contact with a second layer of antiferromagnetic material wherein said second layer of soft material has a unidirectional soft bias direction opposite to said first direction sustained by an exchange interaction relationship with second layer of antiferromagnetic material.
A magnetic thin film transducer including a sandwich composed of a plurality of layers including
- a first pair of layers including a layer of soft magnetic material in direct contact with a layer of antiferromagnetic material wherein said soft material has a unidirectional soft bias direction sustained by an exchange interaction relationship with said antiferromagnetic material,
- a second layer of a soft magnetic material having a unidirectional soft bias direction sustained by an exchange interaction relationship with said antiferromagnetic material.
A magnetic thin film transducer including a sandwich composed of a plurality of layers including
- a first pair of layers including a layer of soft magnetic material in direct contact with a layer of antiferromagnetic material wherein said soft material has a unidirectional soft bias direction sustained by an exchange interaction relationship with said antiferromagnetic material,
- a gap including an intermediate layer of nonmagnetic conductive sensor material,
- a second pair of layers including a second layer of a soft magnetic material in direct contact with a second layer of antiferromagnetic material wherein said second layer of soft material has a unidirectional soft bias direction sustained by an exchange interaction relationship with said second layer of antiferromagnetic material.
A magnetic thin film transducer including a sandwich composed of a plurality of layers including
- a first pair of layers including a layer of soft magnetic material in direct contact with a layer of antiferromagnetic material wherein said soft material has a unidirectional soft bias direction sustained by an exchange interaction relationship with said antiferromagnetic material,
- an intermediate layer of nonmagnetic material, and
- a second layer of a soft magnetic material wherein said second layer of soft material has a soft bias direction sustained by coupling of flux with said first pair of layers.
A magnetic thin film structure including a sandwich composed of a plurality of layers including
- a first pair of layers including a layer of soft magnetic material in direct contact with a layer of antiferromagnetic material wherein said soft material has a unidirectional soft bias direction sustained by an exchange interaction relationship with said antiferromagnetic material,
- an intermediate layer of a nonmagnetic material, and
- a second layer of a soft magnetic material wherein said second layer of soft material has a unidirectional soft bias direction sustained by coupling of flux with said first pair of layers.
A method of forming a magnetic thin film structure comprising depositing a first film of a low coercivity, highly permeable ferromagnetic material upon a substrate, and depositing a second film of an antiferromagnetic material in direct atomic contact with said first film while maintaining a magnetic field upon said first film.
A method of forming a magnetic thin film structure comprising
- depositing a pair of films upon a substrate,
- with a first one of said films comprising a ferromagnetic material with a low coercivity below 10 Oersteds of highly permeable material upon a substrate, and
- a second one of said films comprising an antiferromagnetic material,
- said films being in direct atomic contact with each other, and
- subsequently heating said films above the ordering temperature while maintaining a unidirectional magnetic field applied to said films during cooling thereof producing an exchange interaction relationship between said films with alignment of spins in said antiferromagnetic material and an exchange coupling field H.sub.e greater than the coercivity in the presence of said exchange interaction while retaining low coercivity below 10 Oersteds in said first film.
A method of forming a magnetic thin film structure comprising
- depositing a pair of films upon a substrate with a first film being a ferromagnetic material with a low coercivity below 10 Oersteds, with a high permeability and the second film being an antiferromagnetic material, said first and second films being deposited in direct atomic contact with each other,
- and aligning the spins of said antiferromagnetic material to provide a unidirectional anisotropy in said first film by means of an exchange interaction relationship.
A composition of matter comprising a first material having a low coercivity of less than 10 Oersteds in direct atomic contact with a second material which is antiferromagnetic, with an exchange interaction relationship between said materials provided by alignment of spins in said antiferromagnetic material, and an exchange coupling field H.sub.e greater than the coercivity H.sub.c in the presence of said exchange interaction.
A magnetic thin film transducer including a sandwich composed of a plurality of layers including
- a first pair of layers including a layer of soft magnetic material in direct contact with a layer of antiferromagnetic material wherein said soft material has a unidirectional soft bias direction sustained by an exchange interaction relationship with said antiferromagnetic material,
- a nonmagnetic layer deposited upon said first pair of layers,
- a second pair of layers including a second layer of a soft magnetic material in direct contact with a second layer of antiferromagnetic material wherein said soft material has a unidirectional soft bias direction sustained by an exchange interaction relationship with said second layer of antiferromagnetic material.
Dependencies are inferred from the claim text.