Giant Linear Magnetoelectric Effect at the Morphotropic Phase Boundary of Epitaxial Sr_0.5Ba_0.5MnO₃ films

The search for magnetoelectric multiferroics possessing a strong coupling between their ferroelectric and magnetic properties has attracted great interest, both for technological and fundamental purposes. The understanding of the underlying mechanism behind magnetoelectric coupling is a crucial line of research.
In this work, first-principles calculations are conducted to compute linear magnetoelectric coupling coefficients in epitaxial (001) Sr_0.5Ba_0.5MnO₃ films. A large enhancement of different linear magnetoelectric elements is found in a strained-induced morphotropic phase boundary region which bridges two known tetragonal and orthorhombic states, via a monoclinic state with the continuous rotation of the spontaneous polarization.
The origin of such large enhancement found to originate from the behavior of the dielectric susceptibility, thanks to a simple phenomenological model. Magnetic susceptibility was also determined to influence the linear magnetoelectric coupling. This work provides a promising approach towards designing highly-desired single-phase multiferroic with a colossal magnetoelectric conversion.