Evidence for short-range magnetic order in the nematic phase of FeSe from anisotropic in-plane magnetostriction and susceptibility measurements

TL;DR

This study provides experimental evidence that the nematic phase in FeSe exhibits short-range magnetic order, with anisotropic magnetic susceptibility and magnetostriction measurements indicating a magnetic origin similar to other iron-based superconductors.

Contribution

It demonstrates the presence of frustrated, short-range magnetic order in FeSe's nematic phase through combined anisotropic measurements, supporting a magnetic origin of nematicity.

Findings

Significant in-plane magnetic susceptibility anisotropy in FeSe.

Magnetostriction measurements reveal field-induced in-plane distortion.

Nematic phase in FeSe shows similarities to BaFe2As2, indicating magnetic origin.

Abstract

The nature of the nematic state in FeSe remains one of the major unsolved mysteries in Fe- based superconductors. Both spin and orbital physics have been invoked to explain the origin of this phase. Here we present experimental evidence for frustrated, short-range magnetic order, as suggested by several recent theoretical works, in the nematic state of FeSe. We use a combination of magnetostriction, susceptibility and resistivity measurements to probe the in-plane anisotropies of the nematic state and its associated fluctuations. Despite the absence of long-range magnetic order in FeSe, we observe a sizable in-plane magnetic susceptibility anisotropy, which is responsible for the field-induced in-plane distortion inferred from magnetostriction measurements. Further we demonstrate that all three anisotropies in FeSe are very similar to those of BaFe2As2, which strongly suggests that the nematic phase in FeSe is also of magnetic origin.