Precursor phenomena at the magnetic ordering of the cubic helimagnet FeGe

TL;DR

This study investigates the complex precursor phenomena and phase transitions near the magnetic ordering temperature of the cubic helimagnet FeGe, revealing potential Skyrmion lattice formation and intricate magnetic structures.

Contribution

It provides detailed experimental insights and a phenomenological theory suggesting the existence of a $+\pi$ Skyrmion lattice in FeGe near its magnetic transition.

Findings

Identification of precursor phenomena and phase crossovers near $T_C$

Evidence for a $+\pi$ Skyrmion lattice in the A-phase region

Complex magnetic structures including helicoids in FeGe

Abstract

We report on detailed magnetic measurements on the cubic helimagnet FeGe in external magnetic fields and temperatures near the onset of long-range magnetic order at $T_C= 278.2(3)$ K. Precursor phenomena display a complex succession of temperature-driven crossovers and phase transitions in the vicinity of $T_C$. The A-phase region, present below $T_C$ and fields $H<0.5$ kOe, is split in several pockets. Relying on a modified phenomenological theory for chiral magnets, the main part of the A-phase could indicate the existence of a $+\pi$ Skyrmion lattice, the adjacent A$_2$ pocket, however, appears to be related to helicoids propagating in directions perpendicular to the applied field.