Room temperature electric-field control of magnetism in layered oxides with cation order

Searching for materials with room-temperature electric-field control of magnetism has interested researchers for many years with three-dimensional perovskite BiFeO3-based compounds as the main focus. Here we choose the layered hybrid improper ferroelectric Ruddlesden-Popper oxides as a platform from which to realize electric field controllable magnetism, leveraging a recently identified strain tunable polar-to-nonpolar (P-NP) transition. We first propose a design principle for selecting the required A and B cation chemistries that ensure strained A3B2O7 (001) --oriented films exhibit the P-NP transitions, which we substantiate with density functional calculations. We next extend our guideline to B-site ordered A3BB$\prime $O7 oxides to expand the number of available compounds exhibiting P-NP transitions. We then demonstrate electric-field controllable weak ferromagnetism at the boundary of the P-NP transition in magnetic (001) A3BB$\prime $O7 films and propose new compounds for route to room temperature magnetoelectric multiferroics.