Tuning the superconducting and magnetic properties in Fe_ySe_0.25Te_0.75 by varying the Fe-content

TL;DR

This study investigates how varying Fe content in Fe_ySe_0.25Te_0.75 single crystals influences their superconducting and magnetic properties, revealing that both can be tuned through Fe concentration adjustments.

Contribution

It demonstrates that Fe content, in addition to Se/Te ratio, can be used to control superconductivity and magnetism in FeSeTe compounds, providing new insights into material tuning.

Findings

Superconductivity coexists with incommensurate magnetism for y<1.

Increasing Fe content suppresses superconductivity and enhances magnetic correlation length.

Magnetic order remains incommensurate across the studied Fe content range.

Abstract

The superconducting and magnetic properties of Fe$_{y}$Se$_{0.25}$Te$_{0.75}$ single crystals ($0.9\leq y \leq1.1$) were studied by means of x-ray diffraction, SQUID magnetometry, muon spin rotation, and elastic neutron diffraction. The samples with $y<1$ exhibit coexistence of bulk superconductivity and incommensurate magnetism. The magnetic order remains incommensurate for $y\geq 1$, but with increasing Fe content superconductivity is suppressed and the magnetic correlation length increases. The results show that the superconducting and the magnetic properties of the Fe$_{y}$Se$_{1-x}$Te$_{x}$ can be tuned not only by varying the Se/Te ratio but also by changing the Fe content.