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

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 (ESR) spectroscopy to reconstruct the magnetic anisotropy energy that controls magnetization rotation in Mn3Si2Te6. We show that the low-temperature torque and ESR responses are consistent with a canted ferrimagnetic state, implying higher-order magnetic anisotropies. Importantly, the torque data require additional near-in-plane stiffness beyond the K1-K2 model, which is captured by a finite effective sixth-order term (K3) in the combined ESR-constrained and torque-constrained analysis. Using the resulting anisotropy parameters, we compute the non-linear relation between field angle $${\\theta }_{H}$$ and magnetization angle $${\\theta }_{M}$$ and reparameterize CAMR in terms of $${\\theta }_{M}$$, providing a concrete magnetic basis for how sharp angular transport features can emerge near the in-plane configuration. The interplay between magnetic order and topology in van der Waals materials can lead to extreme responses to external stimuli, yet the underlying spin reorientation mechanisms remain unclear. Here, the authors use thermodynamic torque magnetometry and electron spin resonance spectroscopy to reveal higher-order magnetic anisotropies in Mn₃Si₂Te₆, offering insights into its colossal angular magnetoresistance and potential applications in spintronic devices.