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Subject: Anisotropy × Subject: Thin films ×

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    Magnetically induced anisotropy of flux penetration into strong-pinning superconductor/ferromagnet bilayers
    (Bristol : Institute of Physics Publishing, 2019) Simmendinger, J.; Hanisch, J.; Bihler, M.; Ionescu, A.M.; Weigand, M.; Sieger, M.; Hühne, R.; Rijckaert, H.; Van Driessche, I.; Schütz, G.; Albrecht, J.
    We studied the impact of soft ferromagnetic permalloy (Py) on the shielding currents in a strong-pinning superconductor - YBa2Cu3O7-δ with Ba2Y(Nb/Ta)O6 nano-precipitates - by means of scanning transmission x-ray microscopy. Typically and in particular when in the thin film limit, superconductor/ferromagnet (SC/FM) bilayers exhibit isotropic properties of the flux line ensemble at all temperatures. However, in elements with small aspect ratio a significant anisotropy in flux penetration is observed. We explain this effect by local in-plane fields arising from anisotropic magnetic stray fields originated by the ferromagnet. This leads to direction-dependent motion of magnetic vortices inside the SC/FM bilayer. Our results demonstrate that small variations of the magnetic properties can have huge impact on the superconductor.
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    Mueller matrix imaging microscope using dual continuously rotating anisotropic mirrors
    (Washington, DC : Soc., 2021) Ruder, Alexander; Wright, Brandon; Feder, Rene; Kilic, Ufuk; Hilfiker, Matthew; Schubert, Eva; Herzinger, Craig M.; Schubert, Mathias
    We demonstrate calibration and operation of a Mueller matrix imaging microscope using dual continuously rotating anisotropic mirrors for polarization state generation and analysis. The mirrors contain highly spatially coherent nanostructure slanted columnar titanium thin films deposited onto optically thick titanium layers on quartz substrates. The first mirror acts as polarization state image generator and the second mirror acts as polarization state image detector. The instrument is calibrated using samples consisting of laterally homogeneous properties such as straight-through-air, a clear aperture linear polarizer, and a clear aperture linear retarder waveplate. Mueller matrix images are determined for spatially varying anisotropic samples consisting of a commercially available (Thorlabs) birefringent resolution target and a spatially patterned titanium slanted columnar thin film deposited onto a glass substrate. Calibration and operation are demonstrated at a single wavelength (530 nm) only, while, in principle, the instrument can operate regardless of wavelength. We refer to this imaging ellipsometry configuration as rotating-anisotropic-mirror-sample-rotating-anisotropic-mirror ellipsometry (RAM-S-RAM-E).