Entropic signatures of the skyrmion lattice phase in MnSi1-xAlx and Fe1-yCoySi

TL;DR

This study investigates the entropic signatures of magnetic phase transitions in skyrmion-hosting compounds MnSi1-xAlx and Fe1-yCoySi, revealing differences in transition characteristics linked to disorder and spin dynamics.

Contribution

It provides new insights into the entropic signatures and transition nature of skyrmion lattice phases in these compounds, highlighting non-universality in their phase transitions.

Findings

First order topological phase transition in MnSi0.962Al0.038

Negligible entropic signatures in Fe0.7Co0.3Si due to disorder

Different transition behaviors despite similar magnetic structures

Abstract

The entropic signatures of magnetic phase transitions in the skyrmion lattice host compounds MnSi0.962Al0.038 and Fe0.7Co0.3Si were investigated through low field magnetization and ac susceptibility measurements. These data indicate that the conical to skyrmion transition that occurs with the application of magnetic field in MnSi0.962Al0.038 is characterized by clear discontinuity in the magnetic entropy as expected for first order topological phase transition. These same magnetoentropic features are negligibly small in isostructural Fe0.7Co0.3Si due to the level of chemical substitution related disorder and differences in the spin dynamics (range and timescales). Despite the obvious similarities in the magnetic structures of these two compounds, the transitions between these phases is substantially different indicating a surprising non-universality to the magnetic phase transitions in this class of materials.