Combined molecular dynamics-spin dynamics simulations of bcc iron

7th Brazilian Meeting on Simulational Physics

Perera, Dilina^1 ; Landau, David P.^1 ; Nicholson, Don M.^2 ; Stocks, G Malcolm^2 ; Eisenbach, Markus^2 ; Yin, Junqi^2 ; Brown, Gregory^3

Center for Simulational Physics, University of Georgia, Athens, GA 30602, United States^1

Oak Ridge National Laboratory, Oak Ridge, TN 37831, United States^2

Florida State University, Tallahassee, FL 32306, United States^3

关键词: Correlation function;    Exponential operators;    First principles electronic structure;    Magnetic exchange interactions;    Many-body potentials;    Spin degrees of freedom;    Spin-dependent interactions;    Spinwave excitation;   

Others  :  https://iopscience.iop.org/article/10.1088/1742-6596/487/1/012007/pdf
DOI  :  10.1088/1742-6596/487/1/012007

来源: IOP

【 摘 要 】

Using a classical model that treats translational and spin degrees of freedom on an equal footing, we study phonon-magnon interactions in BCC iron with combined molecular and spin dynamics methods. The atomic interactions are modeled via an empirical many-body potential while spin dependent interactions are established through a Hamiltonian of the Heisenberg form with a distance dependent magnetic exchange interaction obtained from first principles electronic structure calculations. The temporal evolution of translational and spin degrees of freedom was determined by numerically solving the coupled equations of motion, using an algorithm based on the second order Suzuki-Trotter decomposition of the exponential operators. By calculating Fourier transforms of space- and time-displaced correlation functions, we demonstrate that the the presence of lattice vibrations leads to noticeable softening and damping of spin wave modes. As a result of the interplay between lattice and spin subsystems, we also observe additional longitudinal spin wave excitations, with frequencies which coincide with that of the longitudinal lattice vibrations.