Epitaxial Growth of Heusler Co$_{2}$MnSi Heterostructures: Electronic and Structural Properties*

The Heusler alloy Co$_{2}$MnSi is predicted to be a half-metal, a material that is spin-polarized at the Fermi energy. We have demonstrated growth by molecular beam epitaxy of Co$_{2}$MnSi, Cr/Co$_{2}$MnSi, and a complete Co$_{2}$MnSi/MgO/Co$_{2}$MnSi(001) magnetic tunnel junction on epitaxial GaAs(001) surfaces without air exposure. Epitaxial Cr layers have been used to exchange bias Co$_{2}$MnSi. In-situ electron diffraction and scanning tunneling microscopy, and ex-situ X-ray diffraction techniques are used to characterize the crystal quality. The magnetic properties are investigated using vibrating sample and superconducting quantum interference device magnetometry. We present these results and will compare them with temperature dependent magnetotransport and tunneling spectroscopy measurements, with emphasis on the influence of Co$_{2}$MnSi surface termination.