Evidence for in-plane tetragonal c-axis in Mn_xGa_1-x thin films using transmission electron microscopy

Tetragonal Mn_xGa_1-x (x = 0.70, 0.75) thin films grown on SrTiO₃ substrates exhibit perpendicular magnetic anisotropy with coercive fields between 1 and 2 T. Transmission electron microscopy (TEM) and X-ray diffraction (XRD) reveal that 40 nm samples grown at 300-350 °C lead to films with the tetragonal c-axis oriented primarily perpendicular to the film plane but with some fraction of the sample exhibiting the c-axis in the film plane. This structure results in an undesirable secondary magnetic component in the out of plane magnetization. Growth at 300 °C with a reduced thickness or Mn concentration significantly decreases the tetragonal c-axis in the film plane.