A three-order-parameter bistable magnetoelectric multiferroic metal

TL;DR

This paper predicts a new layered-perovskite metal, Bi$_5$Mn$_5$O$_{17}$, as a room-temperature multiferroic with coupled magnetic, electric, and toroidal orders, potentially enabling novel magnetoelectric effects.

Contribution

First-principles calculations reveal Bi$_5$Mn$_5$O$_{17}$ as a stable, multiferroic metal with orthogonal order parameters and strong coupling effects, advancing the design of multifunctional materials.

Findings

Bi$_5$Mn$_5$O$_{17}$ is a ferromagnet, ferroelectric, and ferrotoroid.

It has two nearly degenerate ground states with orthogonal order parameters.

Giant magnetoelectric and magnetotoroidic effects are predicted.

Abstract

Using first-principles calculations we predict that the layered-perovskite metal Bi$_5$Mn$_5$O$_{17}$ is a ferromagnet, ferroelectric, and ferrotoroid which may realize the long sought-after goal of a room-temperature ferromagnetic single-phase multiferroic with large, strongly coupled, primary-order polarization and magnetization. Bi$_5$Mn$_5$O$_{17}$ has two nearly energy-degenerate ground states with mutually orthogonal vector order parameters (polarization, magnetization, ferrotoroidicity), which can be rotated globally by switching between ground states. Giant cross-coupling magnetoelectric and magnetotoroidic effects, as well as optical non-reciprocity, are thus expected. Importantly, Bi$_5$Mn$_5$O$_{17}$ should be thermodynamically stable in O-rich growth conditions, and hence experimentally accessible.