磁性半導体の新材料探索とスピントロニクスへの応用

摘要

In this article, we review recent studies on diluted magnetic semiconductors (DMSs), in which magnetic impurities of either of transition-metal or rare-earth elements are incorporated into semiconductors, mainly focusing on the material search for high-temperature ferromagnetic semiconductors. Even after extensive studies on various DMSs over the past several decades, achieving room-temperature ferromagnetism as an intrinsic property sometimes remains elusive, even with a variety of experimental results of magnetism for the same material. In these situations, it is recognized that the presence or absence of phase separation is an important factor that dominates the magnetic properties, either in the form of precipitation of an extrinsic phase or of non-uniform distribution of magnetic impurities while keeping the coherent structure of the host crystal. We introduce recent studies on the respective materials of DMSs based on III-V, II-VI, IV-VI compounds, and group IV semiconductors, with an emphasis on the correlation between the phase separation and the observed magnetic properties.