Magnetic Structure and Metamagnetic Transitions in the van der Waals Antiferromagnet CrPS₄

In 2D magnets, interlayer exchange coupling is generally weak due to the van der Waals layered structure but it still plays a vital role in stabilizing the long-range magnetic ordering and determining the magnetic properties. Using complementary neutron diffraction, magnetic, and torque measurements, the complete magnetic phase diagram of CrPS₄ crystals is determined. CrPS₄ shows an antiferromagnetic ground state (A-type) formed by out-of-plane ferromagnetic monolayers with interlayer antiferromagnetic coupling along the c axis below T_N = 38 K. Due to small magnetic anisotropy energy and weak interlayer coupling, the low-field metamagnetic transitions in CrPS_4, that is, a spin-flop transition at ≈0.7 T and a spin-flip transition from antiferromagnetic to ferromagnetic under a relatively low field of 8 T, can be realized for H∥c. Intriguingly, with an inherent in-plane lattice anisotropy, spin-flop-induced moment realignment in CrPS₄ for H∥c is parallel to the quasi-1D chains of CrS₆ octahedra. The peculiar metamagnetic transitions and in-plane anisotropy make few-layer CrPS₄ flakes a fascinating platform for studying 2D magnetism and for exploring prototype device applications in spintronics and optoelectronics.