Modulated magnetization depth profile in dipolarly coupled magnetic multilayers

Polarized neutron reflectivity (PNR) and magnetometry studies have been performed on the metal-insulator multilayer [Co80 Fe20 (1.6 nm) Al2 O3 (3 nm)] 9 which exhibits dominant dipolar coupling between the ferromagnetic layers. Our PNR measurements at the coercive field reveal a novel and unexpected magnetization state of the sample, exhibiting an oscillating magnetization depth profile from CoFe layer to CoFe layer with a period of five bilayers along the multilayer stack. With the help of micromagnetic simulations we demonstrate that competition between long- and short-ranged dipolar interactions apparently gives rise to this unprecedented phenomenon.