Epitaxial hard-soft magnetic heterostructures as model exchange-spring magnets

We present investigations of the magnetization reversal process in exchange-spring permanent magnets. Utilizing magnetic heterostructures, such as coupled hard-soft bilayers and multilayers whereby the deposition process provides nanometre-scale control of thickness and magnetic anisotropy, we have constructed a model system for studying the exchange hardening mechanism. Comparison of the experimental results with numerical simulations indicates that the exchange-spring behaviour can be understood from the intrinsic parameters of the hard and soft layers. The simulations are extended to estimate realistically the ultimate gain in performance that can potentially be realized in permanent magnets based on the exchange-spring principle. © 2000 Taylor and Francis Group, LLC.