Diluted Magnetic Semiconductors

Diluted magnetic semiconductors (DMS) are semiconducting crystals whose lattice is made up in part of substitutional magnetic ions (e.g., Cd1_xMnxTe, Hg1_xFexSe, Zn1-xCoxS). In this review we concentrate on materials of the type A“_ xMnxBvl, which are most thoroughly understood. However, we also discuss the similarities and differences of these materials with the A“_xFe(ßw and A111__xCoxBvl systems wherever information on the latter system is available. We discuss the band structure of these materials, which determines their basic semiconducting properties. Special attention is given to exchange interactions between the magnetic ions themselves (the d-d interaction), and the interaction between the magnetic ions and band electrons (the sp-d interaction). Magnetic phenomena in DMS alloys (based on the d-d interaction) are then discussed. Furthermore, we then present phenomena based on the sp-d interaction, such as the giant Faraday rotation, the magnetic-field-induced insulator-to-metal transition, and the bound magnetic polaron. Special attention is given to the physics of layered structures, such as quantum wells and superlattices, involving DMS materials. Finally, we consider the prospects of device applications made possible by the properties of DMS alloys.