References of "Tschöpe, A."
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See detailAngular dependence of coercivity and remanence of Ni nanowire arrays and its relevance to magnetoviscosity
Günther, Annegret UL; Monz, S.; Tschöpe, A. et al

in Journal of Magnetism and Magnetic Materials (2008), 320(7), 1340-1344

Ni nanowire arrays with varying wire dimensions (diameter d, length l) and center-to-center distances dCC were synthesized by pulsed electrodeposition of Ni in porous Al templates. The magnetization ... [more ▼]

Ni nanowire arrays with varying wire dimensions (diameter d, length l) and center-to-center distances dCC were synthesized by pulsed electrodeposition of Ni in porous Al templates. The magnetization-reversal behavior of the arrays was investigated by means of magnetometry for different angles θ between the wire axes and the applied magnetic field. The functional dependences of the characteristic parameters coercivity HC(θ) and reduced remanence mR/mS(θ) exhibit a strong dependence on the wire dimensions and the center-to-center distance. For instance, for nanowire arrays with d=40 nm, dCC=100 nm, and for θ=0°, the coercivity takes on a rather large value of μ0HC=85 mT and mR/mS=94%; reducing dCC to 30 nm and d to 17 nm results in μ0HC=49 mT and mR/mS=57%, an observation which suggests an increasing magnetostatic interwire interaction at increased (d/dCC)-ratio. The potential application of nanowires as the constituents of ferrofluids is discussed. [less ▲]

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See detailUnraveling the nature of room temperature grain growth in nanocrystalline materials
Ames, M.; Markmann, J.; Karos, R. et al

in Acta Materialia (2008), 56

We report on the observation of real-time-resolved room temperature grain growth in nanocrystalline metals. We find that neither the time evolution of size can be modeled by standard growth theories nor ... [more ▼]

We report on the observation of real-time-resolved room temperature grain growth in nanocrystalline metals. We find that neither the time evolution of size can be modeled by standard growth theories nor are there any other systems aware to us that manifest a similar growth behaviour. We detect a transition from an initially self-similar slow growth to abnormal grain growth. Its onset seems to be associated with the simultaneous decrease of microstrain with increasing grain size. Abnormal grain growth is considered as a generic feature of nanocrystallinity but is a transient state since we observed in the late stage of coarsening, using orientational imaging microscopy, a monomodal grain size distribution. We empirically find a nonlinear-response-type of growth law which is in agreement with the observed coarsening kinetics. [less ▲]

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See detailMagnetic Nanorods: Genesis, Self-Organization and Applications
Birringer, R.; Wolf, H.; Lang, C. et al

in Zeitschrift für Physikalische Chemie (2008), 222(2-3), 229-255

Magnetic-field-assisted self-assembly of magnetic dipole moment carrying iron nanoparticles is shown to result in the formation of magnetic and mechanically stiff nanoscale rods. The cooperative behavior ... [more ▼]

Magnetic-field-assisted self-assembly of magnetic dipole moment carrying iron nanoparticles is shown to result in the formation of magnetic and mechanically stiff nanoscale rods. The cooperative behavior of an ensemble of such rods and bundles thereof exhibits self-organized pattern formation on different length scales. Pattern formation on large length scales reveals great similarity with physical systems undergoing spinodal decomposition. Possible applications for dipolar magnetic nanorods in the field of perpendicular storage media are highlighted. We discuss an aerosol-synthesis-route allowing to prepare ferrofluids (FF) with shape-anisotropic particles constituting the magnetic phase immersed in the nonmagnetic carrier fluid. These so-called nanorod FF unveil a two orders of magnitude increase of viscosity enforced by an applied field of 10mT even at shear rates larger than 10-2s. This raises prospects for applications in microfluidics and MEMS. [less ▲]

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See detailThe generalized Cauchy relation: a probe for local structure in materials with isotropic symmetry.
Bactavatchalou, R.; Alnot, Patrick; Baller, Jörg UL et al

in Journal of Physics. Conference Series (2006), 40

The elastic properties of the isotropic state of condensed matter are given by the elastic constants ell and c44. In the liquid state the static shear stiffness c44 vanishes whereas at sufficient high ... [more ▼]

The elastic properties of the isotropic state of condensed matter are given by the elastic constants ell and c44. In the liquid state the static shear stiffness c44 vanishes whereas at sufficient high probe frequencies a dynamic shear stiffness may appear. In that latter case the question about the existence of a Cauchy relation appears. It will be shown that a pure Cauchy relation can appear only under special conditions which are rarely fulfilled. For all investigated materials, including ceramics, liquids and glasses, a linear relation between ell and c44 called generalized Cauchy relation is observed, which, surprisingly, follows a linear transformation. [less ▲]

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