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Author: Seifert, M. Ă— DDC: 530 Ă—

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Now showing 1 - 4 of 4
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    High temperature behavior of rual thin films on piezoelectric CTGS and LGS substrates
    (Basel : MDPI AG, 2020) Seifert, M.
    This paper reports on a significant further improvement of the high temperature stability of RuAl thin films (110 nm) on the piezoelectric Ca3TaGa3Si2O14 (CTGS) and La3Ga5SiO14 (LGS) substrates. RuAl thin films with AlN or SiO2 cover layers and barriers to the substrate (each 20 nm), as well as a combination of both were prepared on thermally oxidized Si substrates, which serve as a reference for fundamental studies, and the piezoelectric CTGS, as well as LGS substrates. In somefilms, additional Al layers were added. To study their high temperature stability, the samples were annealed in air and in high vacuum up to 900 °C, and subsequently their cross-sections, phase formation, film chemistry, and electrical resistivity were analyzed. It was shown that on thermally oxidized Si substrates, all films were stable after annealing in air up to 800 °C and in high vacuum up to 900 °C. The high temperature stability of RuAl thin films on CTGS substrates was improved up to 900 °C in high vacuum by the application of a combined AlN/SiO2 barrier layer and up to 800 °C in air using a SiO2 barrier. On LGS, the films were only stable up to 600 °C in air; however, a single SiO2 barrier layer was sufficient to prevent oxidation during annealing at 900 °C in high vacuum.
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    Phase formation and high-temperature stability of very thin co-sputtered Ti-Al and multilayered Ti/Al films on thermally oxidized si substrates
    (Basel : MDPI AG, 2020) Seifert, M.; Lattner, E.; Menzel, S.B.; Oswald, S.; Gemming, T.
    Ti-Al thin films with a thickness of 200 nm were prepared either by co-sputtering from elemental Ti and Al targets or as Ti/Al multilayers with 10 and 20 nm individual layer thickness on thermally oxidized Si substrates. Some of the films were covered with a 20-nm-thick SiO2 layer, which was used as an oxidation protection against the ambient atmosphere. The films were annealed at up to 800 °C in high vacuum for 10 h, and the phase formation as well as the film architecture was analyzed by X-ray diffraction, cross section, and transmission electron microscopy, as well as Auger electron and X-ray photoelectron spectroscopy. The results reveal that the co-sputtered films remained amorphous after annealing at 600 °C independent on the presence of the SiO2 cover layer. In contrast to this, the γ-TiAl phase was formed in the multilayer films at this temperature. After annealing at 800 °C, all films were degraded completely despite the presence of the cover layer. In addition, a strong chemical reaction between the Ti and SiO2 of the cover layer and the substrate took place, resulting in the formation of Ti silicide. In the multilayer samples, this reaction already started at 600 °C.
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    Stimulated emission and absorption of photons in magnetic point contacts
    (Milton Park : Taylor & Francis, 2012) Naidyuk, Yu G.; Balkashin, O.P.; Fisun, V.V.; Yanson, I.K.; Kadigrobov, A.; Shekhter, R.I.; Jonson, M.; Neu, V.; Seifert, M.; Korenivski, V.
    Point contacts between high anisotropy ferromagnetic SmCo5 and normal metal Cu are used to achieve a strong spin-population inversion in the contact core. Subjected to microwave irradiation in resonance with the Zeeman splitting in Cu, the inverted spin population relaxes through stimulated spin-flip photon emission, detected as peaks in the point-contact resistance. Resonant spin-flip photon absorption is detected as resistance minima, corresponding to sourcing the photon field energy into the electrical circuit. These results demonstrate fundamental mechanisms that are potentially useful in designing metallic spin-based lasers.
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    Domain evolution during the spin-reorientation transition in epitaxial NdCo5 thin films
    (Milton Park : Taylor & Francis, 2013) Seifert, M.; Schultz, L.; Schäfer, R.; Neu, V.; Hankemeier, S.; Rössler, S.; Frömter, R.; Oepen, H.P.
    The domain structure and its changes with temperature were investigated for an epitaxial NdCo5 thin film with in-plane texture in which a spin-reorientation transition takes place from the easy c-axis via the easy cone to the easy plane. Scanning electron microscopy with polarization analysis reveals a transition from a two-domain state at temperatures above 318 K via a four-domain state back to a 90°-rotated two-domain state at temperatures below 252 K. The transition temperatures correspond well to those determined by global magnetization measurements. The magnetization configuration at the three different regimes of magnetic anisotropy and its transition with temperature were analysed in detail. From the local measurements, the spin-reorientation angle and the magnetocrystalline anisotropy constants of first and second order were derived.