An investigation of the interface and bulk contributions to the magneto-optic activity in Co/Pt multi-layered thin films

We report an experimental study that focuses on the magneto-optic interaction between light and perpendicularly magnetized ferromagnetic thin-film multilayers. In this study, samples containing multiple Co/Pt interfaces are measured via the polar magneto-optic Kerr effect. Thanks to a sample set with a continuous Co thickness variation and single and double Co-layered samples, interface and bulk contributions to the magneto-optic activity are separately determined. Kerr rotation and ellipticity signals are recorded as a function of the Co thickness. The results are analyzed via a transfer matrix method that accounts for the standard optical and magneto-optic effects in multi-layered thin-films. Bulk magneto-optic contribution of Co (QCo,bulk) that is in accordance with the literature is consistently determined despite the use of thin-films. Interfacial Co (QCo,int.) and magnetized Pt (QPt) contributions are presented in terms of two models. Interface phenomena of the large spin–orbit coupling between Co and Pt and the proximity induced magnetization in Pt layer are represented in the models. The strength of interfacial magneto-optic activity is interpreted as an indicator of the relative interface quality among the samples.