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

Structural, magnetic and transport properties of diluted magnetic semiconductors, (Ga, Mn)As and (In, Mn)As, have been investigated. Manganese can be substitutionally doped into the group III site of the zincblend structure up to several percent. With Mn content of a few percent, these systems exhibit ferromagnetism at low temperatures. The highest Curie temperature so far achieved is ∼100 K for (Ga, Mn)As. The saturated magnetization values are consistent with S=5/2 local moment, suggesting divalent Mn which acts as an acceptor. The system becomes metallic with increasing Mn content, but a further increase of Mn content tends to decrease the hole density and increase disorder so that the system becomes nonmetallic again at higher Mn concentrations. Large negative magnetoresistance and highly anisotropic transport are observed in the semiconducting samples at low temperatures. The magnetic anisotropy in ultrathin films is found to be strongly affected by the lattice-mismatch-induced strain.