Graded/soft/graded exchange-coupled thin films fabricated by [FePt/C]5/Fe/[C/FePt]5 multilayer deposition and post-annealing

We report the fabrication of exchange-coupled graded/soft/graded films with well-isolated magnetic grains. In contrast to the FePt/Fe exchange spring film, a reduction of up to 72% in coercivity value in the graded/soft/graded film can be obtained. Adding C layers with different thicknesses not only tailors the anisotropy gradient, but also refines the grain size and weakens the intergranular exchange interactions. Micromagnetic simulations reveal that the magnetization reversal proceeds by the propagation of a partial domain wall into the hard FePt layers from the center of the soft Fe layer. The formation of partial domain wall can assist the two graded FePt layers to switch simultaneously, resulting in a lower coercivity.

Highlights► A novel exchange-coupled graded/soft/graded film is developed and then fabricated. ► Large reduction in coercivity is obtained in the graded/soft/graded film. ► Adding C layers can tailor the anisotropy gradient and refine the grain size. ► Magnetization reversal mechanism is revealed by micromagnetic simulations.