Growth, structural, and magnetic properties of single-crystal full-Heusler Co$_{2}$TiGe thin films

Recent predictions have suggested that full-Heusler ferromagnetic Co$_{2}$TiGe may provide a model system for the observation of time-reversal breaking Weyl and nodal line semimetallic behavior. However, to date, few studies have examined the growth of high-quality single crystal thin films of Co$_{2}$TiGe. Consequently, this work presents the growth of Co$_{2}$TiGe thin films by molecular beam epitaxy on conductive n-InP (001) substrates as well as insulating MgO (001) substrates. The surface morphology, structural quality, and magnetic behavior are examined by reflection high-energy electron diffraction, scanning tunneling microscopy, x-ray diffraction, and SQUID magnetometry. The results reveal epitaxial smooth Co$_{2}$TiGe thin films with a terraced layer-by-layer growth mode, a saturation magnetization of \textasciitilde 1.8~$\mu$ B/formula unit, and a Curie temperature of \textasciitilde 375 K. The easy axis was found to lie in the [110] direction but magnetometry also reveals that there is only a small difference in energy between the [110] and [010] magnetization directions, in agreement with theory calculations.