Tunable magnetoelectricity and polarity in van der Waals antiferromagnetic CuCr_1-FeP₂S₆

The coexistence of electric and magnetic orders with intrinsic coupling, referred to as magnetoelectric coupling in multiferroics, has been extensively studied in oxide materials but remains relatively unexplored in van der Waals materials. Among these, CuCrP₂S₆ (CCPS) is notable for its emergent antiferromagnetic (AFM) and antiferroelectric (AFE) characteristics. However, investigations into magnetoelectric coupling in CCPS are limited, and the effects of dopants on its magnetic properties have yet to be fully addressed. In this study, we synthesized CuCr_1-FeP₂S₆ (CCFPS) samples using the chemical vapor transport (CVT) method to investigate the influence of iron doping on the magnetic and nonlinear optical properties of the CCFPS system. Our results indicate that the AFM state is preserved, while the Néel temperature (T_N) varies with the doping concentration. First-principles calculations were employed to assess the exchange interactions among magnetic atoms. Notably, for samples with doping concentrations x < 0.5, we observed both magnetic-dielectric coupling and second harmonic generation (SHG) effects. However, these effects were absent at higher doping levels. Furthermore, our analysis revealed a distinct odd-even dependence of SHG, suggesting the presence of interlayer symmetry-breaking coupling. These findings advance our understanding of two-dimensional (2D) multiferroic materials and lay the groundwork for designing and optimizing magnetoelectric coupling materials with enhanced performance.