Short-range incommensurate magnetic order near the superconducting phase boundary in Fe(1+d)Te(1-x)Se(x)

TL;DR

This study investigates short-range incommensurate magnetic order near the superconducting boundary in Fe(1+d)Te(1-x)Se(x), revealing how magnetic correlations evolve with composition and their relation to superconductivity.

Contribution

It provides new insights into the magnetic ordering phenomena near the superconducting phase boundary in Fe(1+d)Te(1-x)Se(x) compounds using neutron scattering and magnetization measurements.

Findings

Incommensurate magnetic peaks are observed near the AFM wave-vector.

Magnetic order weakens as Se content increases, while superconductivity improves.

Magnetic peaks are asymmetric around the AFM wave-vector, indicating imbalance in magnetic correlations.

Abstract

We performed elastic neutron scattering and magnetization measurements on Fe(1.07)Te(0.75)Se(0.25) and FeTe(0.7)Se(0.3). Short-range incommensurate magnetic order is observed in both samples. In the former sample with higher Fe content, a broad magnetic peak appears around (0.46,0,0.5) at low temperature, while in FeTe(0.7)Se(0.3) the broad magnetic peak is found to be closer to the antiferromagnetic (AFM) wave-vector (0.5,0,0.5). The incommensurate peaks are only observed on one side of the AFM wave-vector for both samples, which can be modeled in terms of an imbalance of ferromagnetic/antiferromagnetic correlations between nearest-neighbor spins. We also find that with higher Se (and lower Fe) concentration, the magnetic order becomes weaker while the superconducting temperature and volume increase.