Competition between commensurate and incommensurate magnetic ordering in Fe(1+y)Te

TL;DR

This study investigates the magnetic ordering in Fe(1+y)Te, revealing a competition between commensurate and incommensurate magnetic states driven by magnetic anisotropy, with implications for understanding iron-based superconductors.

Contribution

The paper demonstrates the coexistence and competition of magnetic orders in Fe(1+y)Te, highlighting a lock-in transition influenced by magnetic anisotropy, which is a novel insight into its magnetic behavior.

Findings

Incommensurate magnetic fluctuations exist above the Neel temperature.

Ordered state exhibits bicollinear and commensurate magnetic order.

Competition between magnetic orders explained by a lock-in transition.

Abstract

The Fe1+y Te1-x Sex compounds belong to the family of iron-based high temperature superconductors, in which superconductivity often appears upon doping antiferromagnetic parent compounds. Unlike other Fe-based superconductors (in which the antiferromagnetic order is at the Fermi surface nesting wavevector [1/2,1/2,1]), the Fe1+y Te1-x Sex parent compound Fe1+y Te orders at a different wavevector, [1/2, 0, 1/2]. Furthermore, the ordering wavevector depends on y, the occupation of interstitial sites with excess iron; the origin of this behavior is controversial. Using inelastic neutron scattering on Fe1.08 Te, we find incommensurate magnetic fluctuations above the Neel temperature, even though the ordered state is bicollinear and commensurate with gapped spin waves. This behavior can be understood in terms of a competition between commensurate and incommensurate order, which we explain as a lock-in transition caused by the magnetic anisotropy.