Ab-initio study of magnetic and electronic properties of the perovskites RFeO_3: 4f-R valence electrons effects

摘要

We involve ab-initio calculations within the generalized gradient approximation (GGA + U) based on the density functional theory (DFT) and Heisenberg Hamiltonian model to study the magnetic phase stability, exchange interactions, electronic and magnetic properties of rare-earth orthoferrites RFeO_3 (R = Dy, Er, Tm). We strongly believe that this model can provide an accurate description of the magnetism in this series of compounds. The 4f-electrons of rare earth elements are treated as valence electrons. In all selected perovskites, 3d shells hybridize with oxygen to form Jahn-Teller distortion, which guarantee superexchange interaction. GGA + U results show that insulating G-AFM configuration is the most appropriate to the spin arrangement of R/Fe ions and agree well with the experimental data. This ground state is typified by small superexchange coupling parameters J_(Fe-Fe) (3.30-3.38 meV) and Neel temperature values (669.93-685.50 K). The volume and the Jahn-Teller distortion (Q3) are responsible to decrease of Jfe-Fe and Neel temperature values when changing R ionic radius. Our results reveal that the 4f valence states are critical factors to properly reproduce the ground state of these compounds.