Patent ID: 7710691

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 comprising a free layer structure; one of the emitter region and the collector region comprising a pinned layer structure; the other one of the emitter region and the collector region comprising an in-stack longitudinal biasing layer structure; the in-stack longitudinal biasing layer structure comprising a first ferromagnetic (FM) pinned layer and a first antiferromagnetic (AFM) pinning layer which magnetically pins the first FM pinned layer; the 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 longitudinally biasing the free layer structure; the pinned layer structure including a second FM pinned layer and a second AFM pinning layer which magnetically pins the second FM pinned layer; 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.