Structure, magnetism, and electron-transport properties of Mn₂CrGa-based nanomaterials

Mn₂CrGa in the disordered cubic structure has been synthesized using rapid quenching and subsequent annealing. The cubic phase transforms to a stable tetragonal phase when a fraction of Cr or Ga is replaced by Pt or Al, respectively. All samples are ferrimagnetic with high Curie temperatures (T_c); Mn₂CrGa exhibits the highest T_c of about 813 K. The tetragonal samples have appreciable values of magnetocrystalline anisotropy energy, which leads to an increase in coercivity (H_c) that approaches about 10 kOe in the Pt-doped sample. The H_c linearly increases with a decrease of temperature, concomitant with the anisotropy change with temperature. All samples are metallic and show negative magnetoresistance with room-temperature resistivities on the order of 1 mΩcm. The magnetic properties including high T_c and low magnetic moment suggest that these tetragonal materials have potential for spin-transfer-torque-based devices.