Predicting a Ferrimagnetic-Ferroelectric Phase of Zn$_{2}$FeOsO$_{6}$ with Strong Magnetoelectric Coupling

Multiferroic materials, in which ferroelectric and magnetic ordering coexist, are of fundamental interest for the development of novel memory devices that allow for electrical writing and non-destructive magnetic readout operation. The great challenge is to create room temperature multiferroic materials with strongly coupled ferroelectric and ferromagnetic (or ferrimagnetic) orderings. BiFeO$_{3}$ has been the most heavily investigated single-phase multiferroic to date due to the coexistence of its magnetic order and ferroelectric order at room temperature. However, there is no net magnetic moment in the cycloidal (antiferromagnetic-like) magnetic state of bulk BiFeO$_{3}$, which severely limits its realistic applications in electric field controlled spintronic devices. Here, we predict that double perovskite Zn$_{2}$FeOsO$_{6}$ is a new multiferroic with properties superior to BiFeO$_{3}$. First, there are strong ferroelectricity and strong ferrimagnetism at room temperature in Zn$_{2}$FeOsO$_{6}$. Second, the easy-plane of the spontaneous magnetization can be switched by an external electric field, evidencing the strong magnetoelectric coupling existing in this system. Our results suggest that ferrimagnetic 3d-5d double perovskite may therefore be used to achieve voltage control of magnetism in future spintronic devices. \\[4pt] [1] P. S. Wang \textit{et al.}, arXiv:1409.8430 (2014).