Room Temperature Electric‐Field Control of Magnetism in Layered Oxides with Cation Order

Abstract

Searching for materials with room‐temperature electric‐field control of magnetism has interested researchers for many years with three‐dimensional perovskite BiFeO 3 ‐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 will ensure (001) A 3 B 2 O 7 films exhibit P‐NP transitions, which we substantiate with density functional calculations. By extending the guideline to B‐site ordered A 3 BB′O 7 oxides, we identify more compounds exhibiting P‐NP transitions marked by the disappearance of an in‐plane polarization that can be functionalized. We then demonstrate that weak ferromagnetism can be tuned by an electric field at the boundary of the P‐NP transition in B‐site ordered (001) A 3 BB′O 7 magnetic films, based on which we predict that cation ordered Ca 3 TcTiO 7 may be a viable candidate for room‐temperature electric‐field control of magnetism.