Magnetotransport in magnetic semiconductors and possible applications

This paper reviews magnetotransport properties of concentrated and diluted magnetic semiconductors, including rare earth chalcogenides, mixed valence manganite perovskites, and the magnetically doped m-V semiconductors. The d ependence of resistivity on state of magnetization leads in several cases t o greater than 12 orders of magnitude decreases in resistivity near the mag netic transition temperature. The concept of the magnetic polaron is introd uced and offers a reasonable explanation for many of these effects. Limitat ions of these materials as magneto-resistive sensors will be discussed. Sev eral novel device geometries based on non-magnetic semiconductors, which ho ld considerable promise for a wide variety of sensor applications will also be mentioned. (C) 2001 Elsevier Science B.V. All rights reserved.