High Pressure studies of the magnetic phase transition in MnSi: revisited

TL;DR

This study revisits the magnetic phase transition in MnSi under high pressure, revealing the sensitivity of magnetic susceptibility to non-hydrostatic stresses and challenging previous claims of a tricritical point.

Contribution

It provides new high-pressure measurements showing the impact of helium solidification on magnetic susceptibility and clarifies the nature of the phase transition in MnSi.

Findings

Magnetic susceptibility curves change abruptly with helium solidification.

Resistivity behavior remains consistent, indicating a first-order transition.

Helium solidification influences magnetic, but not resistivity, measurements.

Abstract

New measurements of AC magnetic susceptibility and DC resistivity of a high quality single crystal MnSi were carried out at high pressure making use of helium as a pressure medium. The form of the AC magnetic susceptibility curves at the magnetic phase transition suddenly changes upon helium solidification. This implies strong sensitivity of magnetic properties of MnSi to non hydrostatic stresses and suggests that the early claims on the existence of a tricritical point at the phase transition line are probably a result of misinterpretation of the experimental data. At the same time resistivity behavior at the phase transition does not show such a significant influence of helium solidification. The sharp peak at the temperature derivative of resistivity, signifying the first order nature of the phase transition in MnSi successfully survived helium crystallization and continued the same way to the highest pressure.