Investigation of half-metallic ferromagnetism in Heusler compounds Co2VZ (ZÂ =Â Ga, Ge, As, Se)

The electronic structures and magnetic properties of 3d transition metal-based full Heusler compounds Co2VZ (Z = Ga, Ge, As, Se) are investigated using the projector augmented wave (PAW) pseudopotential method. By considering the strong localization of Co 3d-states and V 3d-states at the Fermi level, these Co2VZ (Z = Ga, Ge, As, Se) compounds were treated in the framework of the generalized gradient approximation (GGA)+U method, and the results from the conventional GGA method are presented for comparison. The results that were obtained from the density of states with the GGA+U and GGA methods show that the Co2VGa compound is a half-metallic ferromagnet. For the Co2VGe and Co2VAs compounds, the GGA+U method predicts that these two compounds are half-metallic ferromagnetic by shifting the Fermi level to a lower value with respect to the gap in the minority states, when compared to the conventional GGA method. The energy gaps are determined to be 0.283 eV and 0.425 eV, respectively. However, these results show that the density of states of the Co2VSe compound has a metallic character, although the 3d states were corrected when using the GGA+U method. We found that the characteristic of half-metallic ferromagnetism is attributed to the interaction between the V 3d-states other than Co 3d-states. The calculated total magnetic moments are 2.046 μB, 3.054 μB and 4.012 μB respectively for the Co2VZ (Z = Ga, Ge, As) compounds with the GGA+U method. The relationship between total spin magnetic moment per formula unit and total number of valence electrons of these Heusler compounds is in agreement with the Slater-Pauling rule.