From antiferromagnetism to superconductivity in Fe 1+y(Te1-x,Sex) (0 < x < 0.20): a neutron powder diffraction analysis

TL;DR

This study investigates the structural, magnetic, and superconducting phases of Fe1+y(Te1-x,Sex) compounds using neutron diffraction, revealing coexistence of antiferromagnetism and superconductivity in certain compositions.

Contribution

It provides a detailed neutron diffraction analysis of phase transitions and coexistence of magnetic order and superconductivity in FeTe-Se compounds.

Findings

Structural transition from tetragonal to monoclinic is suppressed with increasing Se.

Superconductivity appears for x > 0.05, coexisting with antiferromagnetism.

Long-range antiferromagnetic order is suppressed for x > 0.10.

Abstract

The nuclear and magnetic structure of Fe1+y(Te1-x,Sex) (0 < x < 0.20) compounds was analyzed between 2 K and 300 K by means of Rietveld refinement of neutron powder diffraction data. Samples with x < 0.075 undergo a tetragonal to monoclinic phase transition at low temperature, whose critical temperature decreases with increasing Se content; this structural transition is strictly coupled to a long range antiferromagnetic ordering at the Fe site. Both the transition to a monoclinic phase and the long range antiferromagnetism are suppressed for 0.10 < x < 0.20. The onset of the structural and of the magnetic transition remains coincident with the increase of Se substitution. The low temperature monoclinic crystal structure has been revised. Superconductivity arises for x > 0.05, therefore a significant region where superconductivity and long range antiferromagnetism coexist is present in the pseudo-binary FeTe - FeSe phase diagram.