Perpendicularly magnetized Mn-Co-Ga-based thin films with high coercive   field
  Mn$_{3-x}$Co$_{x}$Ga epitaxial thin films were grown on MgO substrates by magnetron co-sputtering. Structures were tetragonal or cubic depending on Co content. Composition dependence of saturation magnetization and uniaxial magnetic anisotropy $K_u$ of the films were investigated. A high $K_u$ (1.2 MJ m$^{-3}$) was achieved for the Mn$_{2.6}$Co$_{0.3}$Ga$_{1.1}$ film with the magnetic moment 0.84$\mu_B$. Valence band spectra were obtained by hard X-ray photoelectron spectroscopy. Sharp peaks in the cubic case, which were absent in the tetragonal case, prove that a van Hove singularity causes a band Jahn-Teller effect with tetragonal distortion. Observations agree well with the first-principles calculations. 
Siham Ouardi, Takahide Kubota, Gerhard H. Fecher, Rolf Stinshoff,   Shigemi Mizukami, Terunobu Miyazaki, Eiji Ikenaga, and C...
cond-mat.mtrl-sci