  Studying antiferromagnetic domains is essential for fundamental physics and
potential spintronics applications. Despite its importance, few systematic
studies have been performed on van der Waals (vdW) antiferromagnets (AFMs)
domains with high spatial resolutions, and direct probing of the N\`eel vectors
remains challenging. In this work, we found a multidomain in vdW AFM NiPS3, a
material extensively investigated for its exotic magnetic exciton. We employed
photoemission electron microscopy combined with the X-ray magnetic linear
dichroism (XMLD-PEEM) to image the NiPS3's magnetic structure. The
nanometer-spatial resolution of XMLD-PEEM allows us to determine local N\`eel
vector orientations and discover thermally fluctuating N\'eel vectors that are
independent of the crystal symmetry even at 65 K, well below TN of 155 K. We
demonstrate a Ni ions' small in-plane orbital moment anisotropy is responsible
for the weak magneto-crystalline anisotropy. The observed multidomain's thermal
fluctuations may explain the broadening of magnetic exciton peaks at higher
temperatures.
