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Multiscale modeling of magnetic materials: Temperature dependence of the exchange stiffness

By U. Atxitia, D. Hinzke, O. Chubykalo-Fesenko, U. Nowak, H. Kachkachi, O.N. Mryasov, R.F. Evans and R.W. Chantrell


For finite-temperature micromagnetic simulations the knowledge of the temperature dependence of the exchange stiffness plays a central role. We use two approaches for the calculation of the thermodynamic exchange parameter from spin models: (i) based on the domain-wall energy and (ii) based on the spin-wave dispersion. The corresponding analytical and numerical approaches are introduced and compared. A general theory for the temperature dependence and scaling of the exchange stiffness is developed using the classical spectral density method. The low-temperature exchange stiffness A is found to scale with magnetization as m(1.66) for systems on a simple cubic lattice and as m(1.76) for an FePt Hamiltonian parametrized through ab initio calculations. The additional reduction in the scaling exponent, as compared to the mean-field theory (A similar to m(2)), comes from the nonlinear spin-wave effects

Topics: 3104, 2504
Year: 2010
DOI identifier: 10.1103/PhysRevB.82.134440
OAI identifier: oai:eprints.whiterose.ac.uk:42658

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