Magnetic moment of Mn in disordered Pd2MnGe Heusler alloy as studied by CPA and supercell modelling

Abstract

Abstract The neutron-scattering measurements and the observation of hyperfine interaction of nuclear moments in Pd2MnGe alloy have prompted a study of disorder in this compound by the density functional theory methods. Two approaches: the coherent-potential approximation (CPA) and supercell modelling were used to gain microscopic insight into the electronic and magnetic properties of disordered Pd2MnGe. The influence of disorder between Pd and Mn sublattices in Pd2MnGe on the magnetic moment of Mn atoms is discussed. The presented CPA studies have shown that the small disorder in Pd2MnGe (between the Pd-Mn sublattices of the L21 structure) does not well describe the experimental evidence of antiparallel alignment of magnetic moment of Mn at positions (A,C) and B positions. However, the appearance of antiparallel moment of Mn at positions A and B was predicted for the Pd2MnGe in the frames of 128-atoms supercell calculations. The generalized gradient approximation (GGA) has been the main basis for the presented supercell first-principles electronic structure calculations. The magnetic moment of Mn(A,C) is found to be small and negative value of −0.177 µB. The values of magnetic moment of Mn(B) are between 3.6 µB and 3.72 µB. The results obtained for the supercell calculations are consistent with available experiments in the literature. The results of presented calculations in the supercell approach have shown that the disordered Pd2MnGe can be predicted as a mixture of several supercells.