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The influence of magnetocrystalline anisotropy (MCA) on antiferromagnetism is elucidated through the characterization of the spin‒flop transition. However, due to a lack of suitable candidates for investigation, a detailed understanding of the preservation of the spin‒flop transition in the presence of low MCA energy remains elusive. In this study, we introduce CrPS4, which is a two-dimensional van der Waals antiferromagnet, as an ideal system to explore the exceedingly weak limit of the thermally-evolved MCA energy. By employing a uniaxially anisotropic spin model and fitting it to the experimental magnetic properties, we quantify the MCA energy and identify the discernible spin configurations in different magnetic phases. Notably, even at the limit of extremely weak MCA, with a mere 0.12% of the interlayer antiferromagnetic exchange interaction at T= 33 K, which is slightly below the Néel temperature (TN) of 38 K, the spin‒flop transition remains intact. We further establish a direct correlation between the visualized spin arrangements and the progressive reversal of magnetic torque induced by rotating magnetic fields. This analysis reveals the essential role of MCA in antiferromagnetism, thus extending our understanding to previously undetected limits and providing valuable insights for the development of spin-processing functionalities based on van der Waals magnets.

Explorations of van der Waals (vdW) antiferromagnets have revealed new avenues for understanding the fundamentals of highly anisotropic magnetism and realizing spin-based functional properties. However, there is a serious limitation to the feasibility of spintronic applications at room temperature owing to the lack of suitable materials. In this work, we examined the anisotropic magnetic characteristics of Co-doped Fe5GeTe2, a high-TNantiferromagnet with TN= 350 K in which magnetic multilayers are intrinsically formed. Our spin-model calculations with uniaxial anisotropy quantify the magnetocrystalline anisotropy energy and visualize the specific spin arrangements varying in the presence of rotating magnetic fields at room temperature. We further show that the spin configurations can be profoundly relevant to the distinctive evolution of magnetic torques in different magnetic phases. Our advanced approach offers a high-TNvdW antiferromagnet as a magnetic platform to establish room-temperature spin-processing functionalities.

Emerging from competing exchange interactions, the helimagnetic order describes a noncollinear spin texture of antiferromagnets. Although collinear antiferromagnets act as the elemental building blocks of antiferromagnetic (AFM) spintronics, until now, the potential of implementing spintronic functionality in noncollinear antiferromagnets has not been clarified. Here, we propose an AFM helimagnet of EuCo2As2as a novel single-phase spintronic material that exhibits a remarkable sign reversal of anisotropic magnetoresistance (AMR). The contrast in the AMR arises from two electrically distinctive magnetic phases with spin reorientation that is driven by the magnetic field prevailing in the easy plane, which converts the AMR from positive to negative. Furthermore, based on an easy-plane anisotropic spin model, we theoretically identified various AFM memory states associated with the evolution of the spin structure under magnetic fields. The results revealed the potential of noncollinear antiferromagnets for application in the development of spintronic devices.