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Henkel plots in a temperature and time dependent Preisach model.
P. D. Mitchler, E. D. Dahlberg, E. E. Wesseling, R. M. Roshko
IEEE Trans. Magn. 32 p. 3185 (1996).
Abstract: The effect of finite temperature T and observation time t on the Henkel plots of ac and thermally demagnetized systems has been investigated within the framework of a generalized Preisach model, in which it is assumed that thermally activated hopping will occur over all energy barriers W[left angle bracket]W* =k/sub B/TIn(t/ tau /sub 0/), where tau /sub 0/ is a microscopic time, and will systematically drive the Preisach plane towards equilibrium. The Preisach distribution function is assumed to be a factorized product of a Gaussian coercive field distribution, with mean value h/sub c/ and dispersion sigma /sub c/, and a Gaussian interaction field distribution, with a self-consistent mean-field average h/sub int/=km and dispersion sigma /sub s/. Increases in temperature or observation time cause a progressive collapse of the hysteresis cycle, as expected, and also enhance demagnetizing-like curvature in Henkel plots, at least for ac demagnetized systems. An exception is a thermally demagnetized system with k=0, which has a linear Henkel plot independent of W*. Varying the effective time for thermal relaxation of the magnetization from branch to branch of the hysteresis cycle can have the effect of imitating mean field interactions of both magnetizing-like and demagnetizing-like sign in systems with k=0, and can even lead to Henkel plots which violate the lower boundary i/sub d/=-i/sub r/. (13 References).
last modified:
10.Jun.2002
by Thomas Gredig