Magnon spectra of multi-sublattice compounds from first principles.

We investigate the zero-temperature magnon spectra of collinear multi-sublattice magnetic systems using the Holstein-Primakoff formalism. We model the itinerant magnetism from first principles by utilizing exchange parameters derived from density functional theory. The developed theoretical framework-which yields expressions for the magnon dynamical matrix, group velocity and spin-wave stiffness-is then applied to three distinct Heusler compounds: the ferrimagnet Mn2CoAl, the ferromagnet Co2MnSi, and the fully compensated ferrimagnet Mn2LiAl. By successfully capturing behaviors ranging from standard parabolic ferromagnetic dispersions to complex linear antiferromagnetic dynamics, the present formalism provides a systematic framework for evaluating spin-wave parameters.