Neutron diffraction study of MnNiGa2-Structural and magnetic behaviour

MnNiGa2 crystallizes in the L21 (Heusler) structure and has a ferromagnetic ordering temperature T-C similar to 192 K. Rietveld refinement of the neutron diffraction patterns indicates that the Ga atoms occupy the equivalent 8c position, while Mn and Ni share the 4a (0, 0, 0) and 4b (0.5, 0.5, 0.5) sites with a mixed occupancy of Mn and Ni atoms. It is found that that similar to 83% of Mn and similar to 17% Ni are located at the 4a site while similar to 83% of Ni and similar to 17% Mn occupy the 4b site. There is no evidence of a magneto-volume effect around T-C. In agreement with this finding, our detailed critical exponent analyses of isothermal magnetization curves and the related Arrott plots confirm that the magnetic phase transition at T-C is second order. (C) 2014 AIP Publishing LLC.