Probing defects and spin-phonon coupling in CrSBr via resonant Raman scattering

TL;DR

This study uses resonant Raman scattering to analyze defects, vibrational properties, and spin-phonon coupling in CrSBr, revealing defect signatures, environmental effects, and potential for magnetic phase identification in 2D magnets.

Contribution

It provides new insights into defect signatures, environmental degradation, and spin-phonon interactions in CrSBr using resonant Raman spectroscopy, advancing understanding of 2D magnetic materials.

Findings

Distinct vibrational defect signatures identified

Environmental exposure causes intralayer defect formation

Resonant Raman detects magnetic phase and defect fingerprints

Abstract

Understanding the stability limitations and defect formation mechanisms in 2D magnets is essential for their utilization in spintronic and memory technologies. Here, we correlate defects in mono- to multilayer CrSBr with their structural, vibrational and magnetic properties. We use resonant Raman scattering to reveal distinct vibrational defect signatures. In pristine CrSBr, we show that bromine atoms mediate vibrational interlayer coupling, allowing for distinguishing between surface and bulk defect modes. We show that environmental exposure causes drastic degradation in monolayers, with the formation of intralayer defects. Through deliberate ion irradiation, we tune the formation of defect modes, which we show are strongly polarized and resonantly enhanced, reflecting the quasi-1D electronic character of CrSBr. Strikingly, we observe pronounced signatures of spin-phonon coupling of the intrinsic phonon modes and the ion beam induced defect modes throughout the magnetic transition temperature. Overall, we demonstrate that CrSBr shows air stability above the monolayer threshold, and provide further insight into the quasi-1D physics present. Moreover, we demonstrate defect engineering of magnetic properties and show that resonant Raman spectroscopy can serve as a direct fingerprint of magnetic phases and defects in CrSBr.