Crystalline phases in chiral ferromagnets: Destabilization of helical order

TL;DR

This paper explores how weak spin-orbit interactions in chiral ferromagnets can destabilize helical magnetic order, leading to the emergence of crystalline phases similar to blue phases in liquid crystals, with implications for MnSi.

Contribution

It introduces an extended Ginzburg-Landau theory showing the potential for crystalline phases to replace helical order in chiral ferromagnets.

Findings

Crystalline phases based on double-twist cylinders are theoretically predicted.

Blue phases may be relevant in the phase diagram of MnSi.

Destabilization of helical order favors new crystalline arrangements.

Abstract

In chiral ferromagnets, weak spin-orbit interactions twist the ferromagnetic order into spirals, leading to helical order. We investigate an extended Ginzburg-Landau theory of such systems where the helical order is destabilized in favor of crystalline phases. These crystalline phases are based on periodic arrangements of double-twist cylinders and are strongly reminiscent of blue phases in liquid crystals. We discuss the relevance of such blue phases for the phase diagram of the chiral ferromagnet MnSi.