Magnetic phase diagram of MnSi inferred from magnetization and ac susceptibility

TL;DR

This study maps the magnetic phase diagram of MnSi using magnetization and ac susceptibility measurements, revealing a universal skyrmion phase pocket and highlighting the effects of experimental parameters.

Contribution

It provides a comprehensive analysis of the magnetic phases in MnSi, emphasizing the importance of measurement conditions and establishing the skyrmion phase as a universal feature.

Findings

Maxima in dM/dH at phase transitions

Differences between dM/dH and ac susceptibility responses

Universal skyrmion phase pocket in MnSi

Abstract

We report simultaneous measurements of the magnetization and the ac susceptibility across the magnetic phase diagram of single-crystal MnSi. In our study we explore the importance of the excitation frequency, excitation amplitude, sample shape, and crystallographic orientation. The susceptibility, dM/dH, calculated from the magnetization, is dominated by pronounced maxima at the transition from the helical to the conical and the conical to the skyrmion lattice phase. The maxima in dM/dH are not tracked by the ac susceptibility, which in addition varies sensitively with the excitation amplitude and frequency at the transition from the conical to the skyrmion lattice phase. The same differences between dM/dH and the ac susceptibility exist for Mn1-xFexSi (x=0.04) and Fe1-xCoxSi (x=0.20). Taken together our study establishes consistently for all major crystallographic directions the existence of a single pocket of the skyrmion lattice phase in MnSi, suggestive of a universal characteristic of all B20 transition metal compounds with helimagnetic order.