Magnetic Raman Scattering of zig-zag spin chains in AgCrP₂S₆

Low-dimensional quantum magnetic materials host interesting quantum magnetic ground states, such as the Haldane chain for spin-integer systems or spin liquids for spin-half integer systems. Another potential low-dimensional system that may hold interesting quantum magnetic properties is AgCrP₂S₆. It is a van der Waals material from the family of metal thio(seleno)-phosphates (MTPs), where there are alternating zig-zag chains of non-magnetic Ag⁺ (S = 0) and magnetic Cr³⁺ (S = 3/2) ions. Here, we report the observation of magnetic Raman scattering in AgCrP₂S₆ through temperature-dependent and polarization-resolved measurements. We observe a continuum of magnetic excitations with a maximum at ν ≈ 400cm^-1, appearing at temperatures above T_N = 20 K with significant relative intensity in cross-polarization. We compare our observations with theoretical models for the predicted behavior in 1-D chains, as well as to prior experimental reports for other MTPs.