Magnetic detector and method for producing the same
AssigneeAlps Alpine Co., Ltd.
InventorMasamichi Saito
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Abstract
A magnetic detector includes a full-bridge circuit including magnetoresistive sensors on the same substrate. The magnetoresistive sensors include two magnetoresistive films and have different relationships between the fixed magnetization direction and the bias application direction. The fixed magnetization direction and the bias application direction are determined with three or more exchange coupling films including antiferromagnetic layers with different blocking temperatures. Thus, the magnetic detector has high resistance to a strong magnetic field, is easy to produce, and has a high degree of flexibility in production.
Claims21
A magnetic detector comprising a full-bridge circuit including a first magnetoresistive sensor and a second magnetoresistive sensor, the first magnetoresistive sensor including a first magnetoresistive film including a first pinned magnetic layer and a first free magnetic layer, the second magnetoresistive sensor including a second magnetoresistive film including a second pinned magnetic layer and a second free magnetic layer, wherein:
- the full-bridge circuit includes a first half-bridge circuit and a second half-bridge circuit connected in parallel between a power supply terminal and a ground terminal, the first half-bridge circuit including the first magnetoresistive sensor and the second magnetoresistive sensor connected in series, the second half-bridge circuit including the second magnetoresistive sensor and the first magnetoresistive sensor connected in series,
- the first magnetoresistive sensor and the second magnetoresistive sensor are located on the same substrate,
- in the first magnetoresistive film,
- the first pinned magnetic layer and a first pinning antiferromagnetic layer located on an opposite side of the first pinned magnetic layer from the first free magnetic layer constitute a first pinning exchange coupling film, and
- the first free magnetic layer and a first biasing antiferromagnetic layer located on an opposite side of the first free magnetic layer from the first pinned magnetic layer constitute a first biasing exchange coupling film,
- in the second magnetoresistive film,
- the second pinned magnetic layer and a second pinning antiferromagnetic layer located on an opposite side of the second pinned magnetic layer from the second free magnetic layer constitute a second pinning exchange coupling film, and
- the second free magnetic layer and a second biasing antiferromagnetic layer located on an opposite side of the second free magnetic layer from the second pinned magnetic layer constitute a second biasing exchange coupling film,
- the first pinned magnetic layer has a fixed magnetization axis coaxial with a fixed magnetization axis of the second pinned magnetic layer,
- the first biasing exchange coupling film has an exchange coupling magnetic field direction nonparallel to a fixed magnetization axis direction of the first pinned magnetic layer, and the second biasing exchange coupling film has an exchange coupling magnetic field direction nonparallel to a fixed magnetization axis direction of the second pinned magnetic layer,
- each of a blocking temperature Tbf1 of the first pinning antiferromagnetic layer and a blocking temperature Tbf2 of the second pinning antiferromagnetic layer is higher than a blocking temperature Tb1 of the first biasing antiferromagnetic layer and a blocking temperature Tb2 of the second biasing antiferromagnetic layer, and
- the blocking temperature Tb1 of the first biasing antiferromagnetic layer is higher than the blocking temperature Tb2 of the second biasing antiferromagnetic layer.
A method for producing a magnetic detector including a full-bridge circuit including a first magnetoresistive sensor and a second magnetoresistive sensor, the first magnetoresistive sensor including a first magnetoresistive film including a first pinned magnetic layer and a first free magnetic layer, the second magnetoresistive sensor including a second magnetoresistive film including a second pinned magnetic layer and a second free magnetic layer, wherein:
- the full-bridge circuit includes a first half-bridge circuit and a second half-bridge circuit connected in parallel between a power supply terminal and a ground terminal, the first half-bridge circuit including the first magnetoresistive sensor and the second magnetoresistive sensor connected in series, the second half-bridge circuit including the second magnetoresistive sensor and the first magnetoresistive sensor connected in series,
- the first magnetoresistive sensor and the second magnetoresistive sensor are located on the same substrate,
- in the first magnetoresistive film,
- the first pinned magnetic layer and a first pinning antiferromagnetic layer located on an opposite side of the first pinned magnetic layer from the first free magnetic layer constitute a first pinning exchange coupling film, and
- the first free magnetic layer and a first biasing antiferromagnetic layer located on an opposite side of the first free magnetic layer from the first pinned magnetic layer constitute a first biasing exchange coupling film,
- in the second magnetoresistive film,
- the second pinned magnetic layer and a second pinning antiferromagnetic layer located on an opposite side of the second pinned magnetic layer from the second free magnetic layer constitute a second pinning exchange coupling film, and
- the second free magnetic layer and a second biasing antiferromagnetic layer located on an opposite side of the second free magnetic layer from the second pinned magnetic layer constitute a second biasing exchange coupling film,
- each of a blocking temperature Tbf1 of the first pinning antiferromagnetic layer and a blocking temperature Tbf2 of the second pinning antiferromagnetic layer is higher than a blocking temperature Tb1 of the first biasing antiferromagnetic layer and a blocking temperature Tb2 of the second biasing antiferromagnetic layer, and
- the blocking temperature Tb1 of the first biasing antiferromagnetic layer is higher than the blocking temperature Tb2 of the second biasing antiferromagnetic layer,
- the method comprising:
- setting a fixed magnetization axis by ordering the first pinning antiferromagnetic layer and the second pinning antiferromagnetic layer by heat treatment to generate an exchange coupling magnetic field in the first biasing exchange coupling film and in the second biasing exchange coupling film, thereby making a fixed magnetization axis of the first pinned magnetic layer coaxial with a fixed magnetization axis of the second pinned magnetic layer,
- setting a first bias magnetic field by making a direction of a bias magnetic field generated by the first biasing exchange coupling film nonparallel to a fixed magnetization axis direction of the first pinned magnetic layer by heat treatment in an external magnetic field at a temperature lower than a blocking temperature Tbf1 of the first pinning antiferromagnetic layer and a blocking temperature Tbf2 of the second pinning antiferromagnetic layer, and
- after setting the first bias magnetic field, setting a second bias magnetic field by making a direction of a bias magnetic field generated by the second biasing exchange coupling film nonparallel to a fixed magnetization axis direction of the second pinned magnetic layer by heat treatment in an external magnetic field at a temperature lower than the blocking temperature Tb1 of the first biasing antiferromagnetic layer.
Dependencies are inferred from the claim text.