Carrier-Controlled Ferromagnetism in Transparent Oxide Semiconductors

Alex Punnoose, Boise State University
Byung I. Kim, Boise State University
K. M. Reddy, Boise State University
J. O. Holmes, Boise State University

Abstract

The search for an ideal magnetic semiconductor with tunable ferromagnetic behaviour over a wide range of doping or by electrical gating is being actively pursued as a major step towards realizing spin electronics. A magnetic semiconductor having a high Curie temperature, capable of independently controlled carrier density and magnetic doping, is crucial for developing spin-based multifunctional devices. Cr-doped In₂O₃ is such a unique system, where the electrical and magnetic behaviour—from ferromagnetic metal-like to ferromagnetic semiconducting to paramagnetic insulator—can be controllably tuned by the defect concentration. An explicit dependence of magnetic interaction leading to ferromagnetism on the carrier density is shown. A carrier-density-dependent high Curie temperature of 850–930 K has been measured, in addition to the observation of clear magnetic domain structures in these films. Being optically transparent with the above optimal properties, Cr-doped In₂O₃ emerges as a viable candidate for the development of spin electronics.