Multiferroics: different ways to combine magnetism and ferroelectricity

TL;DR

This paper surveys various microscopic mechanisms and material strategies for achieving multiferroicity, focusing on the coexistence of magnetic and ferroelectric properties in single materials, with implications for physics and applications.

Contribution

It introduces new insights into the microscopic origins of multiferroicity, including charge ordering and spiral magnetic structures, and discusses specific material examples like Fe3O4.

Findings

Role of d-state occupation in transition metal perovskites

Importance of spiral magnetic structures

Charge ordering as a ferroelectric mechanism

Abstract

Multiferroics - materials which are simultaneously (ferro)magnetic and ferroelectric, and often also ferroelastic, attract now considerable attention, both because of the interesting physics involved and as they promise important practical applications. In this paper I give a survey of microscopic factors determining the coexistence of these properties, and discuss different possible routes to combine them in one material. In particular the role of the occupation of d-states in transition metal perovskites is discussed, possible role of spiral magnetic structures is stressed and the novel mechanism of ferroelectricity in magnetic systems due to combination of site-centred and bond-centred charge ordering is presented. Microscopic nature of multiferroic behaviour in several particular materials, including magnetite Fe3O4, is discussed.