Comment on: "Ferroelectricity in spiral magnets"

TL;DR

This paper critically examines a recent theory claiming all spiral magnets are ferroelectric, emphasizing the importance of unit cell symmetry in magneto-electric coupling and clarifying conditions for ferroelectricity in such materials.

Contribution

It challenges the generality of Mostovoy's claim by highlighting the role of unit cell symmetry in ferroelectricity of spiral magnets.

Findings

Symmetry of the unit cell is crucial for ferroelectricity in spiral magnets.

Not all spiral magnets are inherently ferroelectric, contrary to previous claims.

Specific symmetry properties are necessary for spiral magnets to exhibit ferroelectricity.

Abstract

There is much interest in the physics of materials that show a strong coupling between magnetic and electric degrees of freedom. In a recent paper by Mostovoy a theory is presented that is based on symmetry arguments and leads to quite general claims which we feel merit some further analysis. In particular, Mostovoy concludes that "spiral magnets are, in general, ferroelectric". We argue that this conclusion is not generally valid, and that the symmetry of the unit cell has to be taken into account by any symmetry-based magneto-electric coupling theory. In an attempt to avoid further confusion in the search of new multiferroic materials, we identify in this Comment some of the necessary symmetry properties of spiral magnets that can lead to ferroelectricity.