Spiral spin-liquid and the emergence of a vortex-like state in MnSc$_2$S$_4$

TL;DR

This paper experimentally confirms the existence of a spiral spin-liquid in MnSc$_2$S$_4$, revealing a vortex-like phase under magnetic field and demonstrating the $J_1$-$J_2$ model's effectiveness for this state.

Contribution

It provides direct neutron scattering evidence for the spiral spin-liquid in MnSc$_2$S$_4$ and uncovers a vortex-like triple-q phase induced by magnetic field.

Findings

Observation of the spiral surface in reciprocal space.

Discovery of a vortex-like triple-q phase under magnetic field.

Validation of the $J_1$-$J_2$ Hamiltonian as a model for the spiral spin-liquid.

Abstract

Spirals and helices are common motifs of long-range order in magnetic solids, and they may also be organized into more complex emergent structures such as magnetic skyrmions and vortices. A new type of spiral state, the spiral spin-liquid, in which spins fluctuate collectively as spirals, has recently been predicted to exist. Here, using neutron scattering techniques, we experimentally prove the existence of a spiral spin-liquid in MnSc$_2$S$_4$ by directly observing the 'spiral surface' - a continuous surface of spiral propagation vectors in reciprocal space. We elucidate the multi-step ordering behavior of the spiral spin-liquid, and discover a vortex-like triple-q phase on application of a magnetic field. Our results prove the effectiveness of the $J_1$-$J_2$ Hamiltonian on the diamond lattice as a model for the spiral spin-liquid state in MnSc$_2$S$_4$, and also demonstrate a new way to realize a magnetic vortex lattice.