Skyrmions and spirals in MnSi under hydrostatic pressure

TL;DR

This study investigates how hydrostatic pressure affects magnetic structures in MnSi, revealing reorientation of magnetic propagation vectors and the persistence of skyrmion lattices despite the loss of long-range order.

Contribution

It provides new insights into the evolution of magnetic correlations and the stability of skyrmions in MnSi under pressure, highlighting mechanisms destabilizing helimagnetic order.

Findings

Helical propagation vector reorients from ⟨111⟩ to ⟨100⟩ with pressure.

Long-range helimagnetic order disappears above critical pressure.

Skyrmion lattices form under magnetic fields even after long-range order vanishes.

Abstract

The archetype cubic chiral magnet MnSi is home to some of the most fascinating states in condensed matter such as skyrmions and a non-Fermi liquid behavior in conjunction with a topological Hall effect under hydrostatic pressure. Using small angle neutron scattering, we study the evolution of the helimagnetic, conical and skyrmionic correlations with increasing hydrostatic pressure. We show that the helical propagation vector smoothly reorients from $\langle 111 \rangle$ to $\langle100\rangle$ at intermediate pressures. At higher pressures, above the critical pressure, the long-range helimagnetic order disappears at zero magnetic field. Nevertheless, skyrmion lattices and conical spirals form under magnetic fields, in a part of the phase diagram where a topological Hall effect and a non-Fermi liquid behavior have been reported. These unexpected results shed light on the puzzling behavior of MnSi at high pressures and the mechanisms that destabilize the helimagnetic long-range order at the critical pressure.