Exchange-spring behavior in epitaxial hard/soft magnetic bilayer films

We present results on the magnetic reversal process in epitaxial Sm-Co(1 (1) over bar 00)/TM (TM=Fe, Co) bilayer films prepared via magnetron sputtering onto Cr-buffered single-crystal MgO substrates. The magnetically hard Sm-Co films have 20 T uniaxial anisotropy and coercivities >3 T at room temperature. The magnetization of the soft layer is pinned at the interface to the hard-magnet layer and switches reversibly as expected for an exchange-spring magnet. With increasing soft layer thickness, the coercive field of the hard layer becomes significantly less than that of a single layer. We also present numerical solutions to a one-dimensional model that provide the spin configuration for each atomic layer. Comparison of the experimental results with the model simulations indicates that the exchange-spring behavior of our bilayer films can be understood from the intrinsic parameters of the hard and soft layers. (C) 1998 American Institute of Physics. [S0021-8979(98)42611-2].