3dtransition metal substituted Fe₃Se₄: prediction of potential permanent magnet

It is crucial for modern condensed matter physics to be able to effectively manipulate magnetism, as well as for permanent applications in general. The pristine Fe₃Se₄is known to meet all the criteria for a good permanent magnet (PM), but its energy product(BH)maxis quite low due to its low magnetization. Based on density functional theory calculations, we report on improved magnetic properties of promising transition metal (TM) substituted Fe₃Se₄systems (TM_0.5Fe_2.5Se₄and TM₁Fe₂Se₄, with TM = Ti, V, Cr, Mn, Fe, Co, Ni, Cu, and Zn). The stability of the compounds is determined using phonon density of states and enthalpy of formation calculations. We predict an enhanced magnetization as well as uniaxial magnetic anisotropy energy (MAE) for TM substituted Fe₃Se₄, reaching a maximum value ofKu= 1.416 MJ m^-3for V₁Fe₂Se₄. We investigate the electronic structure of the compounds, and explore the source of the improved MAE. The enhanced MAE in V₁Fe₂Se₄is attributed to the in-plane 3dorbitals near the Fermi level,E_F, which alters the overall electronic bands. Site-resolved contributions toKushow that the Fe2 sublattice contributes considerably to the overall uniaxial anisotropy in V₁Fe₂Se₄, whereas the Se sublattice contribution shifts from planar anisotropy in Fe₃Se₄to uniaxial. Such improvements in uniaxial MAE, together with improved structural stability, make V₁Fe₂Se₄a promising choice for rare-earth-free PMs.