Structure and Magnetic Properties of （In,Mn）As Based Core-Shell Nanowires Grown on Si（111） by Molecular-Beam Epitaxy

We report the structure and magnetic properties of （In,Mn）As based core-shell nanowires grown on Si （111） by molecular-beam epitaxy. Compared to the core InAs nanowire with a flat side facet and consistent diameter, the core-shell nanowire shows a rough sidewall and an inverse tapered geometry. X-ray diffraction, transmission electron microscopy and energy-dispersive x-ray spectroscopy show that （In,Mn）As is formed on the side facets of In As nanowires with a mixture ofwurtzite and zinc-blende structures. Two ferromagnetic transition temperatures of （In,Mn）As from magnetic measurement data are observed： one is less than 25 K, which could be attributed to the magnetic phase with diluted Mn atoms in the InAs matrix, and the other is at ～300 K, which may originate from the undetectable secondary phases such as MnAs nanoclusters. The synthesis of （In,Mn）As based core-shell nanowires provides valuable information to exploit a new type of spintronic nano-materials.