Advanced tetrahedrally-bonded magnetic semiconductors for spintronic applications

Recent developments of magnetic semiconductors suggest the possibility of harnessing the spin of the electron -in addition to its charge-for future devices and some examples are given here. Highly precise FLAPW calculations demonstrate that: (i) Cd1-xMnxGeP2 chalcopyrites are antiferromagnetically (AFM) favored but will undergo a phase transition to the FM state with n-type S doping. Hence, the magnetic moments (mm) may be tuned with impurities, and a great boon for technological applications; (ii) a new class of half-metallic ferromagnetic semiconductors in Mn doped I-III-VI2 chalcopyrites is predicted with the Curie temperature T-C proportional to the hole concentration. Moreover, we investigated the electronic and magnetic properties of MnxGe1-x as a function of Mn positions in a 64 atom supercell. The FM aligned Mn at a distance of aroot2 has the lowest energy, followed by several energetically competitive FM and AFM configurations, explaining the observation of 'inactive' Mn mm, and the theoretical mm of 3.0 mu(B) per Mn for the FM states. Surprisingly, the exchange interaction between a Mn pair is found to oscillate with the distance between them, and to obey the RKKY analytic formula. In addition, the estimated T-C, around 134-400 K, is in good agreement with experiment. (C) 2003 Elsevier Ltd. All rights reserved.