Comparative study of exchange-correlation functionals for accurate predictions of structural and magnetic properties of multiferroic oxides

Abstract

We systematically compare predictions of various exchange correlation functionals for the structural and magnetic properties of perovskite ${\mathrm{Sr}}_{1\ensuremath{-}x}{\mathrm{Ba}}_{x}{\mathrm{MnO}}_{3} (0\ensuremath{\le}x\ensuremath{\le}1)$---a representative class of multiferroic oxides. The local spin density approximation (LSDA) and spin-dependent generalized gradient approximation with Perdew-Burke-Ernzerhof parametrization (sPBE) make substantial different predictions for ferroelectric atomic distortions, tetragonality, and ground state magnetic ordering. Neither approximation quantitatively reproduces all the measured structural and magnetic properties of perovskite ${\mathrm{Sr}}_{0.5}{\mathrm{Ba}}_{0.5}{\mathrm{MnO}}_{3}$. The spin-dependent generalized gradient approximation with Perdew-Burke-Ernzerhof revised for solids parametrization (sPBEsol) and the charge-only Perdew-Burke-Ernzerhof parametrized generalized gradient approximation with Hubbard $U$ and Hund's $J$ extensions both provide overall better agreement with measured structural and magnetic properties of ${\mathrm{Sr}}_{0.5}{\mathrm{Ba}}_{0.5}{\mathrm{MnO}}_{3}$, compared to LSDA and sPBE. Using these two methods, we find that different from previous predictions, perovskite ${\mathrm{BaMnO}}_{3}$ has large Mn off-center displacements and is close to a ferromagnetic-to-antiferromagnetic phase boundary, making it a promising candidate to induce effective giant magnetoelectric effects and to achieve cross-field control of polarization and magnetism.