Spin-lattice dynamics model with angular momentum transfer for canonical and microcanonical ensembles

• Published in: Physical review. B 2021-01, Vol.103 (2), p.024429, Article 024429
• Main Authors: Strungaru, Mara, Ellis, Matthew O. A., Ruta, Sergiu, Chubykalo-Fesenko, Oksana, Evans, Richard F. L., Chantrell, Roy W.
• Format: Article
• Language: English
• Subjects: Angular momentum; Coupling (molecular); Damping; Energy transfer; Lattice vibration; Magnetic induction; Magnetic relaxation; Magnons; Momentum transfer; Spin dynamics; Spin-orbit interactions
• ISSN: 2469-9950; 2469-9969
• DOI: 10.1103/PhysRevB.103.024429

A unified model of molecular and atomistic spin dynamics is presented enabling simulations both in microcanonical and canonical ensembles without the necessity of additional phenomenological spin damping. Transfer of energy and angular momentum between the lattice and the spin systems is achieved by a phenomenological coupling term representing the spin-orbit interaction. The characteristic spectra of the spin and phonon systems are analyzed for different coupling strength and temperatures. The spin spectral density shows magnon modes together with the uncorrelated noise induced by the coupling to the lattice. The effective damping parameter is investigated showing an increase with both coupling strength and temperature. The model paves the way to understanding magnetic relaxation processes beyond the phenomenological approach of the Gilbert damping and the dynamics of the energy transfer between lattice and spins.