Browsing by Author "Patra, Rajkumar"

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    Charged domains in ferroelectric, polycrystalline yttrium manganite thin films resolved with scanning electron microscopy
    (Bristol : IOP Publ., 2020) Rayapati, Venkata Rao; Bürger, Danilo; Du, Nan; Kowol, Cornelia; Blaschke, Daniel; Stöcker, Hartmut; Matthes, Patrick; Patra, Rajkumar; Skorupa, Ilona; Schulz, Stefan E.; Schmidt, Heidemarie
    We have investigated ferroelectric charged domains in polycrystalline hexagonal yttrium manganite thin films (Y1Mn1O3, Y0.95Mn1.05O3, Y1Mn0.99Ti0.01O3, and Y0.94Mn1.05Ti0.01O3) by scanning electron microscopy (SEM) in secondary electron emission mode with a small acceleration voltage. Using SEM at an acceleration voltage of 1.0 kV otherwise homogenous surface charging effects are reduced, polarization charges can be observed and polarization directions (±Pz) of the ferroelectric domains in the polycrystalline thin films can be identified. Thin films of different chemical composition have been deposited by pulsed laser deposition on Pt/SiO2/Si structures under otherwise same growth conditions. Using SEM it has been shown that different charged domain density networks are existing in polycrystalline yttrium manganite thin films. © 2020 IOP Publishing Ltd.
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    Magnetooptical response of permalloy multilayer structures on different substrate in the IR-VIS-UV spectral range
    (Bristol : IOP Publ., 2019) Patra, Rajkumar; Mattheis, Roland; Stöcker, Hartmut; Monecke, Manuel; Salvan, Georgeta; Schäfer, Rudolf; Schmidt, Oliver G.; Schmidt, Heidemarie
    The magnetooptical (MO) response of Ru/Py/Ta thin film stacks with 4, 8, and 17 nm thick Ni81Fe19 permalloy (Py) films on a SiO2/Si and a ZnO substrate was measured by vector magnetooptical generalized ellipsometry. The MO response from VMOGE was modelled using a 4  ×  4 Mueller matrix algorithm. The wavelength-dependent, substrate-independent and thickness-independent complex MO coupling constant (Q) of Py in the Ru/Py/Ta thin film stacks was extracted by fitting Mueller matrix difference spectra in the spectral range from 300 nm to 1000 nm. Although the composition-dependent saturation magnetization of NixFe1−x alloys (x  =  0.0...1.0), e.g. of Ni81Fe19, is predictable from the two saturation magnetization end points, the MO coupling constant of NixFe1−x is not predictable from the two Q end points. However, in a small alloy range (0.0  <  x  <  0.2 and 0.8  <  x  <  1.0) the composition-dependent Q of NixFe1−x can be interpolated from a sufficiently high number of analyzed NixFe1−x alloys. The available complex MO coupling constants of six different NixFe1−x (x  =  1.0 to 0.0) alloys were used to interpolate MO response of binary NixFe1−x alloys in the range from x  =  0.0 to x  =  1.0.