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peer-reviewed
A general expression for the correlation time of the decay of the magnetization of an assembly of singledomain noninteracting ferromagnetic particles is given in terms of the inverse of the Fokker-Planck operator. The results of Moro and Nordio [G. Moro and P. L. Nordio, Mol. Phys. 56, 255 (1985)], given in the context of dielectric relaxation, are recovered when the Fokker-Planck operator is axially symmetric. Their result is a particular example of Szabo's calculation of the correlation times of the autocorrelation functions of the Legendre polynomials by means of a generalization of the theory of first-passage times [A. Szabo, J. Chem. Phys. 72, 4620 (1980)]. Likewise, the results of Garanin, Ischenko, and Panina (D. A. Garanin, V. V. Ischenko, and L. V. Panina, Teor. Mat. Fiz. 82, 242 (1990) [Theor. Math. Phys. 82, 169 (1990)]) for the integral relaxation time, i.e., the area under the curve of the normalized decay of the magnetization, are regained in the...
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