Covalency, correlations, and inter-layer interactions governing the magnetic and electronic structure of Mn3Si2Te6

Mn3Si2Te6 is a rare example of a layered ferrimagnet. It has recently been shown to host a colossal
angular magnetoresistance as the spin orientation is rotated from the in- to out-of-plane direction,
proposed to be underpinned by a topological nodal-line degeneracy in its electronic structure.
Nonetheless, the origins of its ferrimagnetic structure remain controversial, while its experimental
electronic structure, and the role of correlations in shaping this, are little explored to date. Here, we
combine x-ray and photoemission-based spectroscopies with first-principles calculations, to probe
the elemental-selective electronic structure and magnetic order in Mn3Si2Te6. Through these, we
identify a marked Mn-Te hybridization, which weakens the electronic correlations and enhances the
magnetic anisotropy. We demonstrate how this strengthens the magnetic frustration in Mn3Si2Te6,
which is key to stabilizing its ferrimagnetic order, and find a crucial role of both exchange interactions
extending beyond nearest-neighbours and anti-symmetric exchange in dictating its ordering
temperature. Together, our results demonstrate a powerful methodology of using experimental electronic
structure probes to constrain the parameter space for first-principles calculations of magnetic
materials, and through this approach, reveal a pivotal role played by covalency in stabilizing the
ferrimagnetic order in Mn3Si2Te6.