A helimagnet comprises a noncollinear spin structure formed by competing exchange interactions. Recent advances in antiferromagnet-based functionalities have broadened the scope of target materials to include noncollinear antiferromagnets. However, a microscopic understanding of the magnetic anisotropy associated with the intricate evolution of noncollinear spin states has not yet been accomplished. Here, we have explored the anisotropic magnetic aspects in a layered helimagnet of EuCo2As2 by measuring the magnetic field and angle dependence of the magnetic torque. By adopting an easy-plane anisotropic spin model, we can visualize the detailed spin configurations that evolve in the presence of rotating magnetic fields. This is directly related to the two distinctive magnetic phases characterized by the reversal of the magnetic torque variation across the helix-to-fan transition. Our advanced approach provides an in-depth understanding of the anisotropic properties of noncollinear-type antiferromagnets and a useful guidance for potential applications in spin-processing functionalities.

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-TN antiferromagnet 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-TN vdW antiferromagnet as a magnetic platform to establish room-temperature spin-processing functionalities.