We put forward double perovskites of the $R_2{\text{NiMnO}}_6$ family (with $R$ a rare-earth atom) as a distinct class of multiferroics on the basis of ab initio density-functional calculations. We show that changing $R$ from La to Y drives the ground state from ferromagnetic to antiferromagnetic with $\uparrow \uparrow \downarrow \downarrow$ spin patterns. This ${\text{E}}^{\ast }$-type ordering breaks inversion symmetry and generates a ferroelectric polarization of few microcoulomb per square centimeter. By analyzing a model Hamiltonian, we understand the microscopic origin of this transition and show that an external electric field can be used to tune the transition, thus allowing electrical control of the magnetization.

• Received 13 November 2009

DOI:https://doi.org/10.1103/PhysRevB.82.134429