Spin-phonon coupling and magnon scattering in few-layer antiferromagnetic FePS3

Temperature-dependent Raman spectroscopic studies of spin-phonon (SP) coupling and magnon scattering in bulk and few-layer (FL) antiferromagnet (AFM) FePS3 with Ned temperature (T-N) approximate to 120 K were performed. Bulk and FL (2-5 atomic layers) samples show four distinct modes at room temperature between 150 and 400 cm(-1) and a broad peak at approximate to 105 cm(-1). On lowering the temperature, three distinct phenomena are observed. First, we see the SP coupling, identified by the deviation from the usual two- or three-phonon anharmonic behavior of the higher wave number peaks (>= 150 cm(-1)) at or below T-N. The strength of SP coupling can be calculated for bulk and FL flakes considering mean-field approximations. Secondly, we see the spin ordering marked by the evolution of three peaks at lower wave numbers (around 105 cm(-1)) below T-N due to incommensurate magnetic cells at low temperature. Thirdly, magnon excitation in FL pristine FePS3 is detected by the emergence of a distinct peak at 120 cm(-1) (similar to 3.6 THz) at a temperature much lower than T-N (approximate to 60 K). Tracking the magnon mode in the designed van der Waals heterostructures with Bi2Te3 and Cr2Ge2Te6 reveal interfacial electron and hole transfer from FePS3, respectively. Raman spectroscopy can thus predict the magnetic transition temperature of FL magnetic insulators via SP coupling, zone-boundary phonons, and magnons. Quasi-two-dimensional AFMs and their heterostructures involving different electronic and magnetic orders may be promising candidates for ultrafast magnon transport involving magnetoelastic waves.

Automated summary

Temperature-dependent Raman spectroscopic studies on FePS3 reveal spin-phonon coupling, spin ordering, and magnon excitation phenomena as temperature decreases. Raman spectroscopy can predict the magnetic transition temperature of magnetic insulators and track magnon transport in heterostructures involving different electronic and magnetic orderings.