3d transition metal substituted Fe₃Se₄: prediction of potential permanent magnet

Abstract

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 Fe3Se4 is known to meet all the criteria for a good permanent magnet (PM), but its energy product ( B H ) max is 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 Fe3Se4 systems (TM0.5Fe2.5Se4 and 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 of K u = 1.416 MJ m−3 for V1Fe2Se4. We investigate the electronic structure of the compounds, and explore the source of the improved MAE. The enhanced MAE in V1Fe2Se4 is attributed to the in-plane 3d orbitals near the Fermi level, E F, which alters the overall electronic bands. Site-resolved contributions to K u show that the Fe2 sublattice contributes considerably to the overall uniaxial anisotropy in V1Fe2Se4, whereas the Se sublattice contribution shifts from planar anisotropy in Fe3Se4 to uniaxial. Such improvements in uniaxial MAE, together with improved structural stability, make V1Fe2Se4 a promising choice for rare-earth-free PMs.