Spring magnet films

The properties of exchange-spring-coupled bilayer and superlattice films ar e highlighted for Sm-Co hard magnet (nominally Sm2Co7) and Fe or Co soft ma gnet layers. The hexagonal Sm-Co is grown via magnetron sputtering in a- an d b-axis epitaxial orientations. In both cases the c-axis, in the film plan e, is the easy axis of magnetization. Trends in coercivity with film thickn ess are established and related to the respective microstructures of the tw o orientations. The magnetization reversal process for the bilayers is exam ined by magnetometry and magneto-optical imaging, as well as by simulations that utilize a one-dimensional model to provide the spin configuration for each atomic layer. The Fe magnetization is pinned to that of the Sm-Co at the interface, and reversal proceeds via a progressive twisting of the Fe m agnetization, The Fe demagnetization curves are reversible as expected for a spring magnet. Comparison of experiment and simulations indicates that th e spring magnet behavior can be understood from the intrinsic properties of the hard and soft layers. Estimates are made of the ultimate gain in perfo rmance that can potentially be realized in this system.