Magnetocrystalline anisotropy in Gd(Co,Fe)12B6: A first-principles study

Abstract

The electronic structure, preferential site occupancy for Fe, and magnetocrystalline anisotropy (MCA) have been investigated in Gd(Co12−xFe)xB6via a DFT (density functional theory) plus Hubbard U approach (DFT + U). For Gd atoms, the spin-up 4f bands are fully occupied while the spin-down 4f hole levels are completely empty. The d-like states dominate at the Fermi Level, mainly contributed by Co(Fe) 3d electrons. Co atoms in GdCo12B6 carry magnetic moments of − 0.3 μB and − 0.7 μB at the 18g and 18h sites respectively, while the 7.3 μB Gd moments are ordered antiparallel to the Co(Fe) sublattice. The DFT total energy calculations show that the Fe atoms prefer to replace Co at the 18h site rather than the 18g site, with an energy gain of 0.16 eV/f.u. and they carry a magnetic moment of 1.5 μB/Fe. GdCo12B6 shows a weak easy c− axis MCA (Emca = 90 μeV/f.u.) while GdCo11FeB6 displays a moderate easy ab− plane MCA (Emca = −2690 μeV/f.u.). The spin reorientation induced by Fe doping is related to the electronic structure change near Fermi Level and the different contributions of Co and Fe to the MCA in GdCo12−xFexB6.