Linear magnetoelectricity at room temperature in perovskite superlattices by design

摘要

Discovering materials that display a linear magnetoelectric effect at roomtemperature is challenge. Such materials could facilitate novel devices basedon the electric-field control of magnetism. Here we present simple, chemicallyintuitive design rules to identify a new class of bulk magnetoelectricmaterials based on the 'bicolor' layering of $Pnma$ ferrite perovskites, e.g.,LaFeO$_3$/ LnFeO$_3$ superlattices for which Ln = lanthanide cation. We usefirst-principles density-functional theory calculations to confirm these ideas.Additionally, we elucidate the origin of this effect and show it is a generalconsequence of the layering of any bicolor, $Pnma$ perovskite superlattice inwhich the number of constituent layers are odd (leading to a form of hybridimproper ferroelectricity) and Goodenough- Kanamori rules. Here, the polardistortions induce both weak ferromagnetism and a linear magnetoelectriceffect. Our calculations suggest that the effect is 2-3 times greater inmagnitude than that observed for the prototypical magnetoelectric material,Cr$_2$O$_3$. We use a simple mean field model to show that the consideredmaterials order magnetically above room temperature.