High-field magnetotropic signatures of spin and orbital-current magnetism

Abstract Magnetic anisotropy encodes key information about the angular dependence of the magnetic free energy, but its quantitative characterization often requires probes beyond conventional magnetometry. Magnetotropic susceptibility offers a thermodynamic route to this problem. Here we use quartz tuning-fork resonators to establish the ferromagnet Cr 2 Ge 2 Te 6 as a controlled benchmark for spin-derived magnetic anisotropy and compare it with the kagome metal CsV 3 Sb 5 . Although both systems exhibit pronounced magnetic anisotropy at low temperature and low field, their field evolution is qualitatively distinct. In Cr 2 Ge 2 Te 6 , the full angular and field-dependent response is quantitatively captured by an easy-axis ferromagnetic model. In CsV 3 Sb 5 , by contrast, the anisotropic response persists and strengthens to high magnetic fields, indicating a moment that is not simply spin-ferromagnetic in origin but is instead consistent with the proposed loop-current magnetism. This work indicates high-field magnetotropic susceptibility as a thermodynamic criterion for distinguishing rotatable spin magnetism from possible lattice-locked orbital-current magnetism in correlated quantum materials.