MBE GROWTH OF FERROMAGNETIC METASTABLE EPITAXIAL MNAL THIN-FILMS ON ALAS/GAAS HETEROSTRUCTURES

Epitaxial ferromagnetic films of tau-MnAl in thickness from 3 to 60 nm have been successfully grown on AlAs/GaAs heterostructures using the molecular beam epitaxy (MBE) growth technique. This magnetic phase is a non-equilibrium metastable structure, stabilized in part by its close epitaxial registry with the underlying III-V semiconductor. The growth window is very narrow due to the metastability of the tau-phase. Growth has been achieved through the use of predeposited MnAl template layers of 1-3 bilayers, which effectively separate the nucleation and growth steps. Template formation and subsequent metal growth are monitored by reflection high energy electron diffraction (RHEED). RHEED has also been used to monitor preliminary attempts at III-V semiconductor overgrowth on the magnetic MnAl films. The data indicate that the overgrowth proceeds in a three-dimensional island growth mode of single crystal III-V semiconductor.