Incommensurate short-range order in the S=1 triangular antiferromagnet NiGa2S4

TL;DR

This study uses neutron scattering to reveal incommensurate short-range magnetic order in NiGa2S4, a S=1 triangular antiferromagnet, highlighting complex interactions and persistent glassy phases.

Contribution

It provides detailed characterization of incommensurate short-range order and underlying interactions in NiGa2S4, a system with highly degenerate magnetic states.

Findings

Short-range incommensurate order persists above 1.5 K.

Antiferromagnetic third-nearest neighbor interactions dominate.

Glassy phase persists near the clean limit.

Abstract

Neutron scattering is used to investigate spin correlations in ultra pure single crystals of the S=1 triangular lattice NiGa2S4. Despite a Curie-Weiss temperature of Theta_CW=-80(2) K, static (tau > 1 ns) short range (xi_ab=26(3) \AA) incommensurate order prevails for T>1.5 K. The incommensurate modulation Q_0=(0.155(3),0.155(3),0), Theta_CW, and the spin wave velocity (c=4400 m/s) can be accounted for by antiferromagnetic third-nearest neighbor interactions J_3=2.8(6) meV and ferromagnetic nearest neighbor coupling J_1=-0.35(9) J_3. Inter-plane correlations are limited to nearest neighbors and weakened by an in-plane field. These observations show that the short range ordered glassy phase that has been observed in a number of highly degenerate systems, can persist near the clean limit.