Jahn-Teller distortions as a novel source of multiferroicity

TL;DR

This paper introduces a new mechanism for multiferroicity in specific oxides where Jahn-Teller distortions induce electric polarization, differing from traditional perovskite ferroelectrics, and suggests potential for magnetoelectric effects.

Contribution

It proposes a novel multiferroic mechanism based on Jahn-Teller distortions in noncentrosymmetric oxides with melilite structure, expanding the understanding of multiferroic material design.

Findings

Jahn-Teller distortions can induce electric polarization in certain oxides.

Noncentrosymmetric transition-metal environments enable magnetoelectric coupling.

Potential realization of multiferroic phases with intrinsic magnetoelectric interactions.

Abstract

The Jahn-Teller effect is a fascinating and ubiquitous phenomenon in modern quantum physics and chemistry. We propose a class of oxides with melilite structure Ba$_2$TGe$_2$O$_7$ (T=V,Ni) where Jahn-Teller distortions are the main responsibles for the appearance of electric polarization. At the hearth of the proposed mechanism lies the lack of inversion symmetry displayed by tetrahedrally coordinated transition-metal ions, which allows for the condensation of polar Jahn-Teller distortions, at odds with octahedral coordination typical of conventional ferroelectric oxides with perovskite structure. Since the noncentrosymmetric local environment of transition-metal ions also activates the proposed spin-dependent hybridization mechanism for magnetically-induced electric polarization, proper multiferroic phases with intrinsic magnetoelectric interaction could be realized in this class of low-symmetry materials.