Observation of Three-State Nematicity and Domain Evolution in Atomically Thin Antiferromagnetic NiPS 3 .

Nickel phosphorus trisulfide (NiPS ₃ ), a van der Waals 2D antiferromagnet, has received significant interest for its intriguing properties in recent years. However, despite its fundamental importance in the physics of low-dimensional magnetism and promising potential for technological applications, the study of magnetic domains in NiPS ₃ down to an atomically thin state is still lacking. Here, we report the layer-dependent magnetic characteristics and magnetic domains in NiPS ₃ by employing linear dichroism spectroscopy, polarized microscopy, spin-correlated photoluminescence, and Raman spectroscopy. Our results reveal the existence of the paramagnetic-to-antiferromagnetic phase transition in bulk to bilayer NiPS ₃ and provide evidence of the role of stronger spin fluctuations in thin NiPS ₃ . Furthermore, our study identifies three distinct antiferromagnetic domains within atomically thin NiPS ₃ and captures the thermally activated domain evolution. Our findings provide crucial insights for the development of antiferromagnetic spintronics and related technologies.