New ferromagnetic semiconductor double perovskites: La2FeMO6 (M = Co, Rh, and Ir)

Abstract

Density functional theory with generalized gradient approximation (GGA) plus onsite Coulomb interaction (GGA+U) was used to calculate physical proprieties of new ferromagnetic semiconductor materials of the La2FeMO6 (M=Co, Rh, and Ir). We calculate the 406 (C229) La2MM′O6 compounds which MM′ can be any pair taken from the 29 transition metal elements except La. La2FeCoO6 is a potential candidate for ferromagnetic semiconductor. For the GGA+U scheme, La2FeCo6 remains a stable FM semiconductor, whereas La2FeRhO6 and La2FeIrO6 are shown the FM and AFM states of which are degenerate with each other. The FM semiconductor gap remains in existence under tensile or compressive strain in La2FeRhO6 and La2FeIrO6. The superexchange interaction in ferromagnetic La2FeMO6 (M=Co, Rh, and Ir) is high spin (HS) Fe completely empty eg orbital hopping to the half-filled (LS) Co (Rh and Ir) empty eg orbital.