Origin of the suppression of magnetic order in MnSi under hydrostatic pressure

TL;DR

This study investigates how hydrostatic pressure suppresses magnetic order in MnSi, revealing that the exchange interaction collapse, not quantum fluctuations, causes the transition, and suggesting a reorientation of the magnetic wavevector.

Contribution

It provides experimental benchmarks for first principles theories of strongly correlated systems and highlights the role of exchange interaction collapse in magnetic suppression.

Findings

Magnetic order in MnSi is suppressed at ~1.5 GPa due to J collapse.

Data indicates a reorientation of the magnetic propagation wavevector above ~1.2 GPa.

The suppression is not caused by quantum fluctuation-induced reduction of magnetic moment.

Abstract

We experimentally study the evolution of the magnetic moment $m$ and exchange interaction $J$ as a function of hydrostatic pressure in the zero-field helimagnetic phase of the strongly correlated electron system MnSi. The suppression of magnetic order at $\approx 1.5$~GPa is shown to arise from the $J$ collapse and not from a quantum fluctuations induced reduction of $m$. Our work provides benchmarks for first principles theories that are challenged by the presence of strong correlations and the possible role of Hund's coupling. In addition, our experimental data are consistent with a reorientation of the magnetic propagation wavevector recently evidenced above $\approx 1.2$~GPa. This result calls for a thorough investigation of the crystal structure in this pressure range.