Magnetic charges and magnetoelectricity in hexagonal rare-earth manganites and ferrites

TL;DR

This paper investigates magnetic charges and magnetoelectric effects in hexagonal rare-earth manganites and ferrites, revealing how exchange striction enhances magnetic charges and spin-lattice magnetoelectric responses in these materials.

Contribution

It provides a theoretical analysis of magnetic charges and magnetoelectric constants in hexagonal manganites and ferrites, highlighting conditions for enhanced magnetic charges due to exchange striction.

Findings

Exchange striction induces larger magnetic charges than spin-orbit coupling.

Strong coupling between electric, magnetic, and structural degrees of freedom.

Enhanced in-plane spin-lattice magnetoelectric effects observed.

Abstract

Magnetoelectric (ME) materials are of fundamental interest and show broad potential for technological applications. Commonly the dominant contribution to the ME response is the lattice-mediated one, which is proportional to both the Born electric charge $Z^{\rm e}$ and its analogue, the dynamical magnetic charge $Z^{\rm m}$. Our previous study has shown that exchange striction acting on noncollinear spins induces much larger magnetic charges than those that depend on spin-orbit coupling. The hexagonal manganites $R$MnO$_3$ and ferrites $R$FeO$_3$ ($R$ = Sc, Y, In, Ho-Lu) exhibit strong couplings between electric, magnetic and structural degrees of freedom, with the transition-metal ions in the basal plane antiferromagnetically coupled through super-exchange so as to form a 120$^\circ$ noncollinear spin arrangement. Here we present a theoretical study of the magnetic charges, and of the spin-lattice and spin-electronic ME constants, in these hexagonal manganites and ferrites, clarifying the conditions under which exchange striction leads to an enhanced $Z^{\rm m}$ values and anomalously large in-plane spin-lattice ME effects.