Investigation of atomic anti-site disorder and ferrimagnetic order in the half-metallic Heusler alloy Mn sub(2)VGa

The band structure calculation for the compound Mn sub(2)VGa carried out using the plane wave self-consistent field package with generalized gradient approximation shows that the compound is nearly half-metallic at the equilibrium lattice parameter. However, theoretical investigations have shown that a certain percentage of atomic anti-site disorder can destroy the half-metallic nature of the sample. Hence it is important to quantify the site disorder in these systems. We have deduced the percentage of atomic anti-site disorder from the refinement of the higher angle room temperature (300 K) neutron diffraction (ND) pattern and it was observed to be roughly 8% in our sample. The field variation of resistance recorded at different temperatures shows a positive slope at low temperatures and a negative slope at higher temperatures, indicating the half-metallic character at low temperatures. The ab initio calculations predict a ferrimagnetic ground state for this system. The analysis of the magnetic structure from ND data measured at 6 K yields magnetic moment values of 1.28 mu sub(B) and -0.7 mu sub(B) for Mn and V, respectively, confirming the ferrimagnetic ordering.