Magnetic Properties of Transition-Metal-Doped Silicon Carbide Diluted Magnetic Semiconductors

Abstract

Possibility to employ the spin of electrons for controlling electronic device operation has long been envisaged as a foundation for future extremely low power amplifying and logic devices, polarized light emitting diodes, new generation magnetic field sensors, high density 3D magnetic memories, etc. (Gregg et al., 2002; Žutic et al., 2004; Bratkovsky, 2008). While metal-metal and metal-insulator spin-electronic (or spintronic) devices have already found their application as hard drive magnetic field sensors and niche nonvolatile memories, diluted magnetic semiconductors (DMSs), i.e. semiconductors with a fraction of the atoms substituted by magnetic atoms, are expected to become a link enabling integration of spin-electronic functionality into traditional electron-charge-based semiconductor technology. Following the discovery of carrier-mediated ferromagnetism due to transition metal doping in technologically important GaAs and InAs III-V compound semiconductors (Munekata et at., 1989; Ohno et al., 1996), a wealth of research efforts have been invested in the past two decades into investigations of magnetic properties of DMSs. Ferromagnetic semiconductors were, of course, not new at the time and carrier-mediated ferromagnetism, a lever allowing electrical control of the magnetic ordering, had also been demonstrated albeit only at liquid helium temperatures (Pashitskii & Ryabchenko, 1979; Story et al., 1986). The achievement of the ferromagnetic ordering temperature, the Curie temperature TC, in excess of 100 K in (Ga, Mn) As compounds was a significant step towards practical semiconductor spintronic device implementation. A substantial progress has been achieved in increasing the ordering temperature in this material system and TC as high as 180 K has been reported (Olejnik et al., 2008). (Ga, Mn) As has effectively become a model magnetic semiconductor material with its electronic, magnetic, and optical properties understood most deeply among the DMSs. Still, however, one needs the Curie temperature to be at or above room temperature for most practical applications. Mean-field theory of ferromagnetism (Dietl et al., 2000; Dietl et al., 2001), predicting that above room temperature carrier-mediated ferromagnetic ordering may be possible in certain wide bandgap diluted magnetic semiconductors, including a family of III-nitrides and ZnO, had spun a great deal of interest to magnetic properties of these materials. The resulting 5