Crystal anisotropy implications on the intrinsic magnetic and optical properties in van der Waals FePS3

TL;DR

This study reveals how crystal anisotropy in FePS3 influences its magnetic arrangements and optical properties, showing the importance of anisotropic parameters in understanding and predicting its behavior for spintronic applications.

Contribution

It provides the first detailed correlation between crystal anisotropy and magnetic/optical properties in FePS3, combining experimental observations with theoretical calculations.

Findings

Lateral crystal distortion affects magnetic and optical properties.

Anisotropy causes inversion symmetry breaking and polarization changes.

Temperature influences magnetic arrangements observed via MPL.

Abstract

Antiferromagnetic (AFM) FePS3 has gained significant interest recently for its potential applications in spin-related devices. A single layer is comprised of a honeycomb network, stabilized by long-range spin-exchange interactions, with a zigzag or Neel arrangement of the Fe-atoms. This study exposed, for the first time, a strong impact of lateral crystal distortion on the magnetic arrangement and optical properties of FePS3. This impact was deciphered by correlating photoluminescence (PL) observations with single-crystal XRD which uncovered anisotropy in the a/b crystallographic plane. Thus, induceing a breakage in the inversion symmetry in FePS3 causing changes in it's electronic and optical transitions. The MPL observations exhibited an unexpected band-edge circularly polarized recombination emission, while off-band-edge transitions were linearly polarized. Also, temperature-dependent MPL measurements reflected zigzag-AFM at low temperatures and the coexistence of zigzag or Neel at mid temperatures. Theoretical calculation implementing anisotropy in spin-exchange interactions among Fe atom's nearest neighbors revealed stabilized zigzag arrangement tilted away from the a-axis. Furthermore, DFT calculations of the electronic band-edge predicted split states in degenerate symmetric points (K+/K-) for zigzag structure and non-degenerate for the Neel arrangement. Highlighting the importance of the inclusion of a crystallographic anisotropy parameter for the simulation of the experimental observations.