Ferrimagnetic excitations in the layered hexagonal compound Mn₃Si₂Te₆

The layered ferrimagnet Mn₃Si₂Te₆ orders below T_c=78 K. The S=5/2 Mn sites are arranged in alternating honeycomb and triangular lattice layers. Each honeycomb layer is ferromagnetically ordered with the moments pointing in a singular direction in the ab-plane. The triangular lattice layer has the moments also pointing in the ab-plane but in the opposite direction. A net moment is generated due to an imbalance in the Mn content within the different layer types. We examine single crystal inelastic neutron scattering measurements of the excitations in Mn₃Si₂Te₆ below T_c. We use super-resolution image correlation techniques to refine the resolution convolved spin-wave spectrum in order to determine the exchange interactions in this system. We find significant exchange interactions orthogonal to the ab-plane, produce a network of geometrically frustrated interactions. The potential for Dirac nodes in the dispersion of the coupled ferromagnetic hexagonal layers will also be considered.