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Rotating Anisotropies Without Superparamagnetic Grains in Exchange Bias Systems

Published online by Cambridge University Press:  10 February 2011

T. C. Schulthess*
Center for Computational Sciences and Computer Science and Mathematics Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831–6114, U. S. A.
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We introduce a random field model with anisotropic interfacial exchange for ferromagnet / antiferromagnet bilayers and calculate average coupling energies and coupling directions for different grain or domain sizes. The model is shown to reconcile Malozemoff's random field Ising model for exchange bias with the spinflop coupling mechanism. Furthermore, we find that for small and mid size domains, the average coupling direction strongly varies between different interfacial configurations. We show how this behavior can lead to rotating anisotropies in systems with very strong magnetocrystalline anisotropies, where the use of superparamagnetic grains or domains in the antiferrofmagnet is not justified.

Research Article
Copyright © Materials Research Society 2003

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