Confinement of Chiral Magnetic Modulations in the Precursor Region of FeGe

TL;DR

This study investigates the complex magnetic phase diagram of FeGe near its ordering temperature, revealing precursor states and confined chiral modulations through susceptibility and heat measurements analyzed with Dzyaloshinskii theory.

Contribution

It uncovers the multiplicity of precursor states and the emergence of confined chiral modulations in FeGe near T_C, expanding understanding of magnetic phase transitions in cubic helimagnets.

Findings

Identification of a precursor region around T_C with anomalies in susceptibility.

Observation of a maximum in specific heat indicating a second order transition.

Detection of complex modulated states explained by solitonic interactions.

Abstract

We report on magnetic susceptibility and specific heat measurements of 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. Pronounced anomalies in the field-dependent chi_ac(H) data as well as in the corresponding imaginary part chi"_ac(H) reveal a precursor region around T_C in the magnetic phase diagram. The occurrence of a maximum at T_0=279.6K in the zero-field specific heat data indicates a second order transition into a magnetically ordered state. A shoulder evolves above this maximum as a magnetic field is applied. The field dependence of both features coincides with crossover lines from the field-polarized to the paramagnetic state deduced from chi_ac(T) at constant magnetic fields. The experimental findings are analyzed within the standard Dzyaloshinskii theory for cubic helimagnets. The remarkable multiplicity of modulated precursor states and the complexity of the magnetic phase diagram near the magnetic ordering are explained by the change of the character of solitonic inter-core interactions and the onset of specific confined chiral modulations in this area.