In one illustrative example, a three terminal magnetic sensor (TTM) suitable for use in a magnetic head has a sensor stack structure which includes a base region, a collector region, and an emitter region. A first barrier layer separates the emitter region from the base region, and a second barrier layer separates the collector region from the base region. A plurality of terminals of the TTM include 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. Preferably, the base region consists of a free layer structure so as to have a relatively small thickness. A pinned layer structure is made part of the emitter region. An in-stack longitudinal biasing layer (LBL) structure is formed in stack with the sensor stack structure and has a magnetic moment that is parallel to a sensing plane of the TTM for magnetically biasing the free layer structure. The in-stack LBL structure is made part of the collector region which also includes a layer of semiconductor material. In one variation, the emitter region has the in-stack LBL structure and the collector region has the pinned layer structure. The TTM may comprise a spin valve transistor (SVT), a magnetic tunnel transistor (MTT), or a double junction structure.