The Fe substitution in (M = Si, Ge and Sn): A first-principles study

The preferential site substitution of Fe by Si, Ge and Sn and its effect on magnetic moments have been studied in Nd 2 Fe 14 B by a first-principles density functional calculation. The substitution energies of Si and Ge are positive at the sites of 4e, 8 j 2 and 16 k 1 while the values are negative at the sites of 4c, 8 j 1 and 16 k 2 . However, the substitution energies of Sn are only negative at the sites of 4c and 8 j 1 in Nd 2 ( Fe,Sn ) 14 B . Based on Maxwell–Boltzmann distribution, Si, Ge and Sn prefer strongly to enter the site of 4c and exhibit a moderate preference at the site of 8 j 1 , in good agreement with the powder neutron diffraction results. Upon doping Si, Ge and Sn, the average Fe magnetic moments remain almost unchanged in addition to the dilute effect of the non-magnetic elements of Si, Ge and Sn. The slight enhancement of Nd magnetic moment results from the reduction of the net Nd 5d spin moment, which is antiparallel to the total Nd 4f moment. The reduction of Nd 5d spin moment is ascribed to the hybrid mixing of the Nd 5d electron states and the p electron states of the Si, Ge, and Sn nearest neighbors.