Hard magnetic properties of spacer-layer-tuned NdFeB/Ta/Fe nanocomposite films

Anisotropic Ti(20 nm)/NdFeB(100 nm)Nd(10 nm)/Ta(x nm)/Fe(y nm)/Ti(20 nm) multilayer films were prepared, and the magnetic coupling mechanism between soft-/hard-magnetic (SM/HM) layers were systematically studied in order to understand the potential of anisotropic SM/HM nanocomposite magnets. Recoil behaviors were also investigated in films with various thicknesses of Fe layer. From experimental results, the roles of exchange coupling and magnetostatic coupling in the demagnetization process were clarified, which was further supported by micromagnetic simulations. For different thicknesses of Ta spacer layer, the demagnetization process was analyzed, and the coupling energy was estimated. This work also indicated that, using the proper thickness of Ta spacer layer, the (BH)max can be enhanced in the SM/HM nanocomposite magnets by a combination of weakened exchange coupling and magnetostatic coupling.