Atomistic Spin Dynamics

The LDA+U calculated MAE and Js were used in atomistic spin dynamics simulations, which are based on the Landau-Lifshitz-Gilbert (LLG) equation (for more details see M. Ellis et. al). This work was done in collaboration with Dr Mathew Ellis.

The antiferromagnetic (AFM) phase transition and the magnon dispersion relation resulting from the spin dynamics calculations are presented in the figure above. The stability tests for the ground state spin order coincide with the experimentally observed double hexagonal magnetic cell with propagation vector. The phase transition occurs at approximately 55 K, in good agreement with the experimental value of 53 K.

The magnon spectra were calculated for the high symmetry points path (for the HCP Brillouin Zone). The lower frequency spectra at the Γ point correspond to approximately 2 meV (~ 16 cm^-1), which agrees with the experimentally observed excitations reported previously by Skiadopoulou et.al.. Further calculations are planned with application of external magnetic field, to test both the excitations and the magnetic phase transitions.