Hard/soft magnetic heterostructures: model exchange-spring magnets

An overview is provided of research on exchange-spring coupled magnetic films and multilayers, including fabrication methods, and the characterization and modeling of the magnetization reversal processes. For coupled hard/soft bilayers and multilayers the deposition process provides nanometer-scale control of thicknesses and magnetic anisotropy. Such magnetic heterostructures provide model systems for studying the exchange hardening mechanism. Recent work on epitaxial SmCo/Fe and SmCo/Co bilayers and superlattices that display many of the characteristic features of exchange-spring magnets is highlighted. Comparison of the experimental results with numerical simulations indicates that the exchange-spring behavior can be understood from the intrinsic parameters of the hard and soft layers. The simulations are extended to realistically estimate the ultimate gain in performance that can potentially be realized in permanent magnets based on the exchange-spring principle. (C) 1999 Published by Elsevier Science B.V. All rights reserved.