Diluted magnetic semiconductors based on II–VI, III–VI, and IV–VI compounds

Abstract

Chemical and phase composition, magnetic susceptibility, SIMS, magnetic force microscopy, and neutron diffraction data for Ge1−x−ySnxMnyTe, InSe⟨Mn⟩, and ZnO⟨Co, Mn⟩ single crystals are investigated over a wide range of temperatures and magnetic fields. For Ge1−x−ySnxMnyTe the existence of ferromagnetic (FM) ordering with a Curie temperature TC∼50K, due to an indirect exchange interaction between Mn ions via the degenerate hole gas, is established. It is shown that at T<50K the ferromagnetic regions of the crystal form a spin-glass phase. In InSe⟨Mn⟩ it is found that hysteresis loops of the magnetic moment M(H) are observed up to 350K. They attest to the existence of ferromagnetic ordering, which is apparently due to ferromagnetic clusters in which a superexchange of the Mn ions via the Se anions is proposed, and to an indirect interaction via the 2D electron gas. At T<70K a period doubling of the magnetic sublattice of α-MnSe second-phase inclusions is observed, and their distribution in the layered structure of the InSe⟨Mn⟩ host matrix has a regular character, forming a self-organized FM∕AFM superlattice. In ZnO⟨Co, Mn⟩ the temperature dependence of M obeys a Curie law. When the solubility limit of Co in ZnO is exceeded, hysteresis loops are observed as a consequence of the appearance of a ferromagnetic second phase. In ZnO⟨Mn⟩ samples and also in some ZnO⟨Co⟩ samples with Co content below the solubility limit an antiferromagnetic (AFM) interaction takes place.