Metal-insulator transition and magnetotransport in III-V compound diluted magnetic semiconductors

Structural, magnetic and transport properties of diluted magnetic semicondu ctors, (Ga, Mn)As and (In, Mn)As, have been investigated. Manganese can be substitutionally doped into the group III site of the zincblend structure u p to several percent. With Mn content of a few percent, these systems exhib it ferromagnetism at low temperatures. The highest Curie temperature so far achieved is similar to 100 K for (Ga, Mn)As. The saturated magnetization v alues are consistent with S = 5/2 local moment, suggesting divalent Mn whic h acts as an acceptor. The system becomes metallic with increasing Mn conte nt, but a further increase of Mn content tends to decrease the hole density and increase disorder so that the system becomes nonmetallic again at high er Mn concentrations. Large negative magnetoresistance and highly anisotrop ic transport are observed in the semiconducting samples at low temperatures . The magnetic anisotropy in ultrathin films is found to be strongly affect ed by the lattice-mismatch-induced strain. (C) 1999 Elsevier Science B.V. A ll rights reserved.