Structural dependence of the physical properties for Co2MnGa Heusler alloy films

In this study, Co2MnGa Heusler alloy (HA) films with significantly different structural orders were fabricated, and the influence of structural ordering on various physical properties was investigated. Co2MnGa films were deposited by flash evaporation onto glass substrates at various substrate temperatures from 150 to 753 K. A disordered state of the films was achieved by using a vapor-quenching deposition at 150 K. Deposition at 623 K or post annealing of the disordered film at 728 K resulted in the formation of an intermediate structural order. As the substrate or the post-annealing temperature was decreased, a slight increase in the lattice constants was observed. We also found that the grain size increased in the films deposited at higher substrate temperatures. The ordered and intermediately ordered films exhibit ferromagnetic behavior and similar equatorial Kerr effect (EKE) spectra. Similar to the previously studied Ni-based HA films, the disordered film is nonmagnetic and has little EKE response. An annealing of the disordered film restores its crystalline structure and recovers the ferromagnetic order.