Dynamic approach for micromagnetics close to the Curie temperature.pdfVIP

Dynamic approach for micromagnetics close to the Curie temperature 1 2 2 3 O. Chubykalo-Fesenko , U. Nowak , R. W. Chantrell , and D. Garanin 1 Instituto de Ciencia de Materiales de Madrid, CSIC, Cantoblanco, 28049 Madrid, Spain 2 Department of Physics, University of York, York YO10 5DD, UK and 3 Department of Physics and Astronomy, Lehman College, City University of New York, 6 250 Bedford Park Boulevard West, Bronx, New York 10468-1589, U.S.A. 0 (Dated: February 3, 2008) 0 2 In conventional micromagnetism magnetic domain configurations are calculated based on a con- tinuum theory for the magnetization which is assumed to be of constant length in time and space. r p Dynamics is usually described with the Landau-Lifshitz-Gilbert (LLG) equation the stochastic vari- A ant of which includes finite temperatures. Using simulation techniques with atomistic resolution we show that this conventional micromagnetic approach fails for higher temperatures since we find 1 two effects which cannot be described in terms of the LLG equation: i) an enhanced damping when 2 approaching the Curie temperature and, ii) a magnetization magnitude that is not constant in time. We show, however, that both of these effects are naturally described by the Landau-Lifshitz-Bloch ] equation which links the LLG equation with the theory of critical phenomena and turns out to be i c a mo