Sulfur-induced magnetism in FeSe$_{1-x}$S$_x$ thin films on LaAlO$_3$ revealed by muon spin rotation/relaxation

TL;DR

This study reveals that sulfur substitution induces low-temperature magnetism in FeSe$_{1-x}$S$_x$ thin films, with muon spin rotation/relaxation showing magnetic fluctuations linked to S content and temperature, highlighting complex interactions in iron chalcogenides.

Contribution

It provides the first detailed investigation of sulfur-induced magnetism in FeSe$_{1-x}$S$_x$ thin films using muon spin rotation/relaxation, comparing effects of chemical and physical pressure.

Findings

S substitution induces low-temperature magnetism in FeSe$_{1-x}$S$_x$ films.

Magnetic fluctuations decrease with increasing S content.

Anomaly temperature increases with S content.

Abstract

Muon spin rotation/relaxation measurements were performed to investigate magnetic properties of FeSe$_{1-x}$S$_x$ thin films on LaAlO$_3$. A drastic decrease of the initial asymmetry was observed together with the peak structure in the temperature dependence of the relaxation rate of muon spins almost at the same temperature where kink anomalies were observed in the temperature dependent resistivity. With increasing S content, the anomaly temperature increased and the magnetic fluctuations at the lowest temperature were suppressed. These results show that the S substitution induces magnetism at low temperatures in FeSe$_{1-x}$S$_x$ thin films. Although the behaviors of the magnetic and nematic phases in FeSe films towards chemical pressure by S substitution are similar to those for bulk FeSe towards hydrostatic pressure, the behavior of $T_{\mathrm c}$ is significantly different between these systems. Our results demonstrate that the detailed comparative investigation among physical and chemical pressure effects is essentially important to understand the interplay of the magnetism, the nematicity and the superconductivity in iron chalcogenides.