Magnetic anisotropy and transport properties of epitaxially grown MnAs/GaAs digital alloys

An enhancement of both Tc and the magnetic anisotropy, as well as unusual electrical transport properties, are observed in superlattice thin films consisting of metallic ferromagnet MnAs and semiconducting GaAs. Structural analysis indicates that the MnAs layer is hexagonal rather than zinc blende. All films studied display room temperature ferromagnetism with a Tc higher than that of a single-layer MnAs film. A MnAs(5 nm)/GaAs(5 nm) superlattice showed the highest Tc (345 K) and the largest magnetic anisotropy. Furthermore, the temperature-dependent resistance of this sample shows semiconductor-like behavior and exhibited negative magnetoresistance, suggesting an interplay between the charge carriers and localized magnetic ions.