We have successfully grown ferromagnetic MnGa ultrathin films on GaAs substrates by molecular beam epitaxy. Reflection high energy electron diffraction and cross-sectional transmission electron microscopy show that monocrystalline MnGa films are grown with the c axis of the tetragonal unit cell normal to the (001) GaAs substrates. Both magnetization measurements by vibrating sample magnetometer and extraordinary Hall effect (EHE) measurements indicate perpendicular magnetization, with the remnant magnetization of 225 emu/cm3 and EHE resistivity in the range of 0.5–4 μΩ cm at room temperature. The material possesses properties ideal for certain nonvolatile magnetic memory coupled with underlying III-V circuitry.

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Scanning force microscopy study of the surface topography of thin BaTiO3 films deposited by pulsed laser ablation J.Microstructural evolution and preferred orientation change of radiofrequencymagnetron sputtered ZnO thin films

We have grown a new class of epitaxial metallic multilayers consisting of ultrathin ferromagnetic tetragonal MnGa and nonmagnetic (CsCl-type) NiGa on (001) GaAs substrates by molecular beam epitaxy. Reflection high energy electron diffraction and cross-sectional transmission electron microscopy analyses show that MnGa/NiGa multilayers with atomically abrupt interfaces are formed with the expected epitaxial orientations, and, in particular, that the c-axis of the tetragonal structure of the MnGa film is aligned perpendicular to the substrate. Perpendicular magnetization of the MnGa/NiGa multilayers was evidenced by both vibrating sample magnetometer and extraordinary Hall effect measurements at room temperature, with higher values (Mr=267–302 emu/cm3) of remanent magnetization than those of previously reported MnGa and MnAl thin films. The capability of growing this new class of materials will allow a new degree of artificial materials design on semiconductor substrates.