Spin-dependent tunneling and properties of ferromagnetic (Ga,Mn)As (invited)

Low-temperature molecular beam epitaxy allows one to dope GaAs with Mn over its solubility limit, making it possible to realize a III–V-based diluted magnetic semiconductor (Ga,Mn)As. Magnetization measurements revealed that (Ga,Mn)As is ferromagnetic at low temperatures. The ferromagnetic transition temperature [formula omitted] can be as high as 110 K for 5% Mn. Magnetotransport properties of (Ga,Mn)As were found closely related to its magnetic properties. The temperature and magnetic-field B dependence of resistivity ρ can be understood in terms of spin-dependent scattering. The [formula omitted] exchange determined from the B dependence of ρ is shown to be consistent with the exchange expected from [formula omitted] based on the Ruderman–Kittel–Kasuya–Yosida interaction. The anomalous Hall effect dominates the Hall resistance up to room temperature, allowing one to determine the magnetic properties from the magnetotransport measurements alone. Since (Ga,Mn)As can be grown pseudomorphically on GaAs, one can introduce ferromagnetism in GaAs-based heterostructures such as resonant tunneling diodes and observe spin-dependent phenomena in current–voltage characteristics. Magneto-optical properties of (Ga,Mn)As films are also presented.