Coherent canted ferrimagnetism and higher-order anisotropy in the nodal-line magnetic semiconductor Mn3Si2Te6

Abstract: The interplay between magnetic order and electronic topology in van der Waals materials enables extreme responses to external stimuli. The nodal-line semiconductor Mn3Si2Te6 exemplifies this, exhibiting colossal angular magnetoresistance (CAMR) where resistivity changes by orders of magnitude upon rotating the magnetic field. While this phenomenon implies a profound coupling between spin orientation and charge transport, the microscopic magnetic potentials driving spin orientations remain elusive. Here, we combine thermodynamic torque magnetometry and electron spin resonance spectroscopy to reconstruct the magnetic anisotropy energy that controls magnetization rotation in Mn3Si2Te6. We show that low-temperature ground state is a coherent canted ferrimagnet stabilized by competing second- (K1) and fourth-order (K2) magnetic anisotropy. Crucially, torque requires a substantial symmetry-allowed sixth-order term (K3), which provides near-plane stiffness and sustains canting at high fields. Using the resulting anisotropy parameters, we compute the non-linear relation between field angle θ_H and magnetization angle θ_M and reparameterize CAMR in terms of θ_M, providing a concrete magnetic basis for how sharp angular transport features can emerge near the in-plane configuration.