Spin reorientation in TlFe1.6Se2 with complete vacancy ordering

TL;DR

This study reveals how vacancy ordering influences magnetic orientation in TlFe1.6Se2, showing a clear in-plane magnetic ground state in fully ordered crystals and complex behavior in mixed regions, impacting understanding of superconducting analogues.

Contribution

It demonstrates the direct link between vacancy order and magnetic reorientation in TlFe1.6Se2, challenging the phase separation paradigm in intercalated iron selenides.

Findings

Fully ordered crystals have Fe moments in the ab-plane below 100K.

Partially disordered crystals show competing magnetic orientations.

Coupling between ordered and disordered regions affects magnetic properties.

Abstract

The relationship between vacancy ordering and magnetism in TlFe1.6Se2 has been investigated via single crystal neutron diffraction, nuclear forward scattering, and transmission electron microscopy. The examination of chemically and structurally homogenous crystals allows the true ground state to be revealed, which is characterized by Fe moments lying in the ab-plane below 100K. This is in sharp contrast to crystals containing regions of order and disorder, where a competition between c-axis and ab-plane orientations of the moments is observed. The properties of partially-disordered TlFe1.6Se2 are therefore not associated with solely the ordered or disordered regions. This contrasts the viewpoint that phase separation results in independent physical properties in intercalated iron selenides, suggesting a coupling between ordered and disordered regions may play an important role in the superconducting analogues.