Magnetic multilayers with competing in plane and out of plane anisotropies

Abstract

Multilayers formed by layers with different anisotropy conform one of the most interesting kinds of magnetic multi-layered systems. In particular, multilayers combining films with in plane and out of plane anisotropy provide a wide range of magnetic properties depending on the dominant anisotropy and the degree of coupling between the layers. When employed as spacers, some metals can induce a strong modulation in the coupling, which can be controlled using different spacer thicknesses. Here, we report on a particular system consisting of a perpendicular magnetic anisotropy (PMA) [Co/Pd]n multilayer with an in-plane shape anisotropy Permalloy (Py) layer. Our multi-layered system is grown by sputtering and its magnetic properties studied by Magneto-optical Kerr effect (MOKE) and magnetic force microscopy (MFM). To achieve tuneable magnetization angles and tailor the degree of coupling, we employ a non- magnetic spacer of variable thickness (ruthenium). The PMA of the multilayers can be enhanced by increasing the number of units, adding an additional degree of freedom. In this study, we vary systematically the [Co/Pd]n multilayer structure and spacer thickness. The magnetic coupling is investigated combining magnetization measurements by MOKE at room temperature in longitudinal and polar configuration, thus measuring in plane and out of plane magnetization, with MFM to get the domain structure.