Magnetotransport in magnetic epitaxial metal layers buried in (Ga, Al)As heterostructures (invited) (abstract)

Incorporation of magnetic, metallic quantum wells in semiconductors has added new dimensions to epitaxial heterostructures. Magnetotransport experiments explore the interplay of bandstructure, quantum confinement, dimensionality and magnetism. Rare earth monoarsenides, like ErAs, have been grown as buried layers in GaAs. The material is a semimetallic antiferromagnet that exhibits spin disorder scattering at the Néel point. By diluting the ErAs with ScAs, lattice matching to GaAs can be achieved and these materials exhibit Shubnikov-de Haas (SdH) oscillations. The exchange interaction between the conduction band and the 4f spin deduced from SdH agrees with that derived from spin disorder scattering. Surprisingly, down to 2 monolayers, quantum confinement does not convert the semimetal into a semiconductor. This is not understood. But, the Neel point can be seen to drop by a factor of two by following the spin disorder scattering. In the few monolayer regime the magnetotransport can change its character and is more aptly described by bound magnetic polarons. More recently, ferromagnetic, metastable, τMnAl layers have also been grown on GaAs. Thin layers of τMnAl grow in such a way that the tetragonal axis is perpendicular to the interface. The extraordinary Hall effect and longitudinal magnetotransport confirm that the moment has the desired property of being oriented perpendicular to the interface. © 1991, American Institute of Physics. All rights reserved.