First-principles study of a pressure-induced spin transition in multiferroic Bi2FeCrO6

Abstract

We report on a first-principles study of the structural, electronic, and magnetic properties of multiferroic double perovskite Bi${}_{2}$FeCrO${}_{6}$, using density functional theory within the local spin-density approximation (LSDA), the LSDA+U approximation as well as a hybrid functional scheme. We show that Bi${}_{2}$FeCrO${}_{6}$ presents two competing ferrimagnetic phases, sharing the same total magnetic moment of 2${\ensuremath{\mu}}_{B}$ per unit cell but with a different electronic configuration for the Fe${}^{3+}$ species. The phase with high-spin iron is the ground state at ambient conditions, but we predict that low-spin iron gets stabilized under compression. We also investigate the corresponding ferromagnetic phases, and show that the magnetic couplings sharply decrease when moving form high- to low-spin Fe${}^{3+}$.