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

Abstract

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.