Probing Intrinsic Magnetic Phases in Low‐Dimensional Nearly Twin‐Free NiPS 3 Single Crystals

ABSTRACT We report the intrinsic thermal and magnetic properties of the low‐dimensional van der Waals (vdW) antiferromagnet NiPS 3 and explore its emergent magnetic phases by controlling crystallographic twinning. Using nearly twin‐free crystals, we resolve intrinsic properties that are typically obscured by multidomain effects in bulk samples. Magnetization results reveal a highly anisotropic, sharp spin‐flop transition, confirming the high domain purity of our crystals. Furthermore, high‐precision thermodynamic and transport data reveal a broad fluctuation regime around the Néel temperature ( T N = 157.5 K), with a heat capacity anomaly and a concurrent suppression of thermal conductivity. Field‐dependent thermal transport shows a small but distinct contribution from spin‐lattice coupling, as evidenced by the dip at the spin‐flop transition. We develop a theoretical model to explain these properties reported in this paper, with good agreement between experiment and theory. Our work establishes a definitive baseline for bulk properties of NiPS 3 and demonstrates the feasibility of resolving intrinsic anisotropies by addressing crystallographic twinning in vdW magnets.