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Publisher: Bristol : IOP × Subject: Density functional theory ×

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    Mechanical properties and twin boundary drag in Fe-Pd ferromagnetic shape memory foils-experiments and ab initio modeling
    (Bristol : IOP, 2011) Claussen, I.; Mayr, S.G.
    We report on vibrating reed measurements combined with density functional theory-based calculations to assess the elastic and damping properties of Fe-Pd ferromagnetic shape memory alloy splats. While the austenite-martensite phase transformation is generally accompanied by lattice softening, a severe modulus defect and elevated damping behavior are characteristic of the martensitic state. We interpret the latter in terms of twin boundary motion between pinning defects via partial 'twinning' dislocations. Energy dissipation is governed by twin boundary drag, primarily due to lattice imperfections, as concluded from the temperature dependence of damping and related activation enthalpies.
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    Experimental electronic structure of In2O3 and Ga2O3
    (Bristol : IOP, 2011) Janowitz, C.; Scherer, V.; Mohamed, M.; Krapf, A.; Dwelk, H.; Manzke, R.; Galazka, Z.; Uecker, R.; Irmscher, K.; Fornari, R.; Michling, M.; Schmeißer, D.; Weber, J.R.; Varley, J.B.; Van De Walle, C.G.
    Transparent conducting oxides (TCOs) pose a number of serious challenges. In addition to the pursuit of high-quality single crystals and thin films, their application has to be preceded by a thorough understanding of their peculiar electronic structure. It is of fundamental interest to understand why these materials, transparent up to the UV spectral regime, behave also as conductors. Here we investigate In2O3 and Ga2O3, two binary oxides, which show the smallest and largest optical gaps among conventional n-type TCOs. The investigations on the electronic structure were performed on high-quality n-type single crystals showing carrier densities of ∼1019 cm-3 (In2O3) and ∼1017 cm-3(Ga2O3). The subjects addressed for both materials are: the determination of the band structure along high-symmetry directions and fundamental gaps by angular resolved photoemission (ARPES). We also address the orbital character of the valence- and conduction-band regions by exploiting photoemission cross.