High-temperature multiferroicity and strong magnetocrystalline anisotropy in 3d-5d double perovskites

Using density functional calculations we explore the properties of as-yet-unsynthesized 3d-5d ordered double perovskites (A(2)BB'O-6) with highly polarizable Bi3+ ions on the A site. We find that the Bi2NiReO6 and Bi2MnReO6 compounds are insulating and exhibit a robust net magnetization that persists above room temperature. When the in-plane lattice vectors of the pseudocubic unit cell are constrained to be orthogonal (for example, by coherent heteroepitaxy), the ground states are ferroelectric with large polarization and a very large uniaxial magnetocrystalline anisotropy with easy axis along the ferroelectric polarization direction. Our results suggest a route to multiferroism and electrically controlled magnetization orientation at room temperature.