ONLINE - PhD Mid-term Seminar Series: Magneto-optical signal dependence on Co-layer thickness asymmetry in Co/Pt/Co-films

CIC nanoGUNE Seminars

Ramon Weber, Nanomagnetism Group
nanoGUNE online Webinar
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ONLINE - PhD Mid-term Seminar Series: Magneto-optical signal dependence on Co-layer thickness asymmetry in Co/Pt/Co-films **** **Magneto-optical signal dependence on Co-layer thickness asymmetry in Co/Pt/Co-films** Ramon Weber Nanomagnetism Group, CIC nanoGUNE ** ** Ever since the first observation of interlayer exchange coupling, magnetic multilayers have been a research subject of tremendous importance, leading to many surprising phenomena. In a recent study, Tomita et al. [1] showed that the magneto-optical response in Fe/Pt multilayers can enhance substantially if the thickness stacking is varied non-periodically. This effect could not be explained by classical electromagnetic theory assuming local material dependent dielectric properties, but might be related to quantum mechanical interferences associated with non-periodic stacking of nm-scale magnetic films and their resulting quantum well states. We fabricated a series of Co/Pt/Co bilayer structures with pre-defined and variable thickness asymmetry of the Co layers. The optical and magneto-optical properties of these films were measured using Generalized Magneto-optical Ellipsometry. In addition to a Co/Pt interface proximity effect that leads to an overall enhancement of the magneto-optical response, we do not find the initially expected quadratic effect, but instead observe a strong linear effect. We also compare our experimental results to a classical optics description based upon the transfer matrix method and we can achieve agreement in between these calculations and our experimental data only, if we assume massively anomalous optical wave attenuation in Pt. Otherwise, the unexpected strong linear effect, whose origin must be associated with the collective nature of quantum mechanical electronic states in asymmetric trilayers, cannot be mapped onto a classical optics model. Furthermore, it has been proven by our group [2], that nanostructured arrays, e.g., holes in a magneto-optical active metallic film, can be designed to generate surface plasmon polariton bands that leads to a marked enhancement of the magneto-optical response. Within this surface plasmon polariton band engineering approach, we might be able to gain a substantial increase in performance of magneto-plasmonic devices, which is the overall aim of the project. **References** [1] S. Tomita, T. Suwa, P. Riego, A. Berger, H. Nobuyoshi, and H. Yanagi, Phys. Rev. Appl. 11, 064010 (2019). [2] N. Maccaferri, X. Inchausti, A. García-Martín, J. C. Cuevas, D. Tripathy, A. O. Adeyeye, and P. Vavassori, ACS Photonics **2** (12), 1769-1779 (2015). \---------- Please **REGISTER** for PhD Mid-term Seminar Series on Sep 7, 2020 11:00 AM CEST at: After registering, you will receive a confirmation email containing information about joining the webinar. Thank you very much for your participation!