Specific heat of the skyrmion lattice phase and field-induced tricritical point in MnSi

TL;DR

This study provides high-precision measurements of the specific heat in MnSi, confirming the skyrmion lattice as a thermodynamic phase and identifying a tricritical point that supports a fluctuation-induced first order transition.

Contribution

It offers detailed thermodynamic evidence for the skyrmion lattice phase and the tricritical point in MnSi, supporting the Brazovskii transition theory.

Findings

Confirmation of skyrmion lattice as a thermodynamic phase

Identification of a tricritical point at 340mT and 28.5K

Evidence supporting a fluctuation-induced first order transition

Abstract

We report high-precision measurements of the temperature and magnetic field dependence of the specific heat, C(T,H), across the magnetic phase diagram of MnSi. Clear anomalies establish the skyrmion lattice unambiguously as a thermodynamic phase. The evolution of the specific heat anomalies, the field dependence of the entropy released at the phase transitions, and the temperature versus field dependence of crossover lines provide striking evidence of a tricritical point at an internal magnetic field of 340mT and temperature of 28.5K. The existence of this tricritical point represents strong support of a helimagnetic Brazovskii transition, i.e., a fluctuation-induced first order transition at H = 0.