Browsing by Author "Samwer, Konrad"

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    Characterization of geometrically frustrated Zn1-xMn xAl2O4 thin films prepared by metalorganic aerosol deposition [Articol]
    (2009) Sanchez, Rodolfo; Saleta, Martin Eduardo; Șapoval, Oleg; Gehrke, Kai; Moșneaga, Vasilii; Samwer, Konrad
    We present the results on the structure and magnetoelectric properties of Zn1−xMnxAl2O4 thin films (0 ≤ x ≤ 1), prepared by metalorganic aerosol deposition (MAD) technique. The films have been grown epitaxially on MgO(100) substrates and characterized by X-ray diffraction (XRD), Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray analysis (EDX), magnetization, electron paramagnetic resonance (EPR) and capacitance as a function of temperature and magnetic field. For large x values (x = 0.75 and 1), we observed a deviation of the magnetization from a Curie-Weiss law below 40K, indicating the expected magnetic ordering of the spinel. In the proximity of this magnetic characteristic temperature the capacitance as a function of temperature shows a peak, which infers a multiferroic character of these spinels.
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    Giant negative photoconductivity in La0.7Ca 0.3MnO3 thin films [Articol]
    (2004) Moșneaga, Vasilii; Giske, Arnold; Samwer, Konrad; Mișina, Elena; Tamura, Takehisa; Nakabayashi, Seiichiro; Belenciuc, Alexandr; Șapoval, Oleg; Culiuc, Leonid
    The increase of the resistance up to two orders of magnitude under laser illumination (l5760 nm) was observed in La0.7Ca0.3MnO3 ~LCMO! epitaxial thin films in ferromagnetic state.Optical absorption also increases by 10–15 % and the magnetic second-harmonic generation signal decreases down to zero under the irradiation. The light induced changes are reversible with decreases down to zero under the irradiation. The light induced changes are reversible with characteristic relaxation times t;1 – 30 s. Magnetic field, B54 T, suppresses the photoconductivity and decreases its relaxation time. Photoinduced effects are caused by the injection of a large number of extra carriers, which change the ~antiferromagnetic! AFM/FM phase balance in LCMO, favoring the insulating AFM state.