Magnetization process in SmFe-NiFe exchange spring films

Summary form only given. The magnetization reversal in a sputtered Sm/sub 40/Fe/sub 60/ (88 nm)/Ni/sub 80/Fe/sub 20/ (62 nm) bilayer film with induced uniaxial anisotropy was investigated by Kerr microscopy. The low-anisotropy NiFe film is exchange coupled to the high-anisotropy amorphous SmFe film, leading to a double-step easy-axis hysteresis curve as typical for an exchange spring film system. After saturation and field inversion, the magnetization in the soft film is continuously twisted across the film thickness, with the magnetic moments at the interface being fixed along the previous saturation direction by exchange interaction with the (still rigidly magnetized) hard layer.