Critical behavior of van der Waals topological ferromagnet CrVI6

CrVI6 is a recently proposed van der Waals topological magnetic material derived from its parent compounds, CrI3 and VI3, via elemental substitution. However, beyond initial proposals of its topological nature, the fundamental characteristics of its magnetic ordering remain largely unexplored. Investigating the critical behaviors of a magnet provides deep insight into its underlying spin interactions and universality class. In this work, we synthesized high-quality CrVI6 single crystals, demonstrating strong perpendicular magnetic anisotropy below the Curie temperature (∼58.2 K) via DC magnetization and heat capacity measurements. The critical magnetic behavior in the vicinity of the paramagnetic to ferromagnetic phase transition region has been systematically analyzed using multiple approaches, yielding the critical exponents β = 0.294(8), γ = 0.947(9), and δ = 4.21(5). These values do not conform to any single universality class but instead demonstrate a distinct crossover behavior between the three-dimensional Ising and tricritical mean-field models. This crossover is indicative of complex magnetic ordering, characterized by the coexistence of short-range and long-range exchange interactions. Further analysis using renormalization group theory quantifies the decay of the exchange interaction J(r)≈r−4.80, confirming the behavior consistent with the crossover model. Our findings establish a comprehensive picture of the fundamental spin correlations in CrVI6, highlighting it as a fertile platform for developing future quantum and spintronic applications.