Temperature dependent Raman study of antiferromagnetic CrPS4

The temperature dependence of the Raman spectrum of exfoliated CrPS4 samples was investigated by polarized Raman spectroscopy with three excitation sources between 4 K and room temperature (293 K). The peak positions and the polarization dependences of the 14 observed Raman modes are consistent with the previous report at room temperature. However, there are some critical changes in the Raman spectrum at low temperatures. For the bulk sample, the mode at ∼306 cm−1 is polarized along the b-axis of the crystal at room temperature but is slightly polarized along the a-axis at low temperatures. In addition, a mode at ∼188 cm−1 emerges, and its intensity increases dramatically below the Néel temperature. Both of these changes were most prominent with a 2.41 eV excitation source. Similar changes were observed in few-layer samples down to 2-layers.