Patent ID: 7639459

Claim:
A three terminal magnetic sensor (TTM), comprising: a sensor stack structure comprising a base region, a collector region, and an emitter region; a first barrier layer located between the emitter region and the base region; a second barrier layer located between the collector region and the base region; a plurality of terminals of the TTM comprising a base lead coupled to the base region, a collector lead coupled to the collector region, and an emitter lead coupled to the emitter region; the collector region comprising a layer of semiconductor material; the base region being made of ferromagnetic materials and including: a free layer structure; a pinned layer structure; a first non-magnetic spacer layer located between the free layer structure and the pinned layer structure; an in-stack longitudinal biasing layer structure being formed in stack with the sensor stack structure and having a magnetic moment that is parallel to a sensing plane of the TTM for longitudinal biasing the free layer structure; a second non-magnetic spacer layer located between the free layer structure and the in-stack longitudinal biasing layer structure; an insulator layer which is offset from the sensing plane and in between the base region and the collector region; and a layer of metal which is offset from the sensing plane and in contact with the ferromagnetic materials of the base region, the layer of metal having an electrical resistivity of less than 10 uΩ-centimeters so that a combined electrical resistivity of the base region is between about 2-18 uΩ-centimeters.