Bi-collinear antiferromagnetic order in the tetragonal $\alpha$-FeTe

TL;DR

This paper uses first-principles calculations to identify a bi-collinear antiferromagnetic ground state in tetragonal $ ext{FeTe}$, driven by complex superexchange interactions, contrasting with the collinear order in $ ext{FeSe}$.

Contribution

It reveals the bi-collinear antiferromagnetic order in $ ext{FeTe}$ and explains its origin through superexchange interactions, providing new insights into magnetic structures of iron chalcogenides.

Findings

$ ext{FeTe}$ exhibits bi-collinear antiferromagnetic order.

The magnetic order results from superexchange interactions $J_1$, $J_2$, and $J_3$.

Contrast with $ ext{FeSe}$'s collinear antiferromagnetic order.

Abstract

By the first-principles electronic structure calculations, we find that the ground state of PbO-type tetragonal $\alpha$-FeTe is in a bi-collinear antiferromagnetic state, in which the Fe local moments ($\sim2.5\mu_B$) are ordered ferromagnetically along a diagonal direction and antiferromagnetically along the other diagonal direction on the Fe square lattice. This bi-collinear order results from the interplay among the nearest, next nearest, and next next nearest neighbor superexchange interactions $J_1$, $J_2$, and $J_3$, mediated by Te $5p$-band. In contrast, the ground state of $\alpha$-FeSe is in the collinear antiferromagnetic order, similar as in LaFeAsO and BaFe$_2$As$_2$.