Freigelegt! Mit einer templatgestützten Elektroabscheidung gelang die Synthese stabiler Netzwerke aus Metall‐ oder Halbleiternanodrähten (siehe Schema). Dazu wurde a) mesoporöses Siliciumdioxid an einer Elektrode abgeschieden, b) die Kanäle mit dem Metall oder Halbleiter gefüllt und c) das Templat entfernt, um das Nanodrahtnetz zu erhalten.

No abstract

X-band ferromagnetic resonance (FMR) was used to characterize in-plane magnetic anisotropies in rectangular and square arrays of circular nickel and Permalloy microdots. In the case of a rectangular lattice, as interdot distances in one direction decrease, the in-plane uniaxial anisotropy field increases, in good agreement with a simple theory of magnetostatically interacting uniformly magnetized dots. In the case of a square lattice a four-fold anisotropy of the in-plane FMR field Hr was found when the interdot distance a gets comparable to the dot diameter D. This anisotropy, not expected in the case of uniformly magnetized dots, was explained by a non-uniform magnetization m(r) in a dot in response to dipolar forces in the patternedmagnetic structure. It is well described by an iterative solution of a continuous variation procedure. In the case of perpendicular magnetization multiple sharp resonance peaks were observed below the main FMR peak in all the samples, and the relative positions of these peaks were independent of the interdot separations. Quantitative description of the observed multiresonance FMR spectra was given using the dipole-exchange spin wave dispersion equation for a perpendicularly magnetized film where in-plane wave vector is quantized due to the finite dot radius, and the inhomogenetiy of the intradot static demagnetization field in the nonellipsoidal dot is taken into account. It was demonstrated that ferromagnetic resonance force microscopy (FMRFM) can be used to determine both local and global properties of patterned submicron ferromagnetic samples. Local spectroscopy together with the possibility to vary the tip-sample spacing enables the separation of those two contributions to a FMRFM spectrum. The global FMR properties of circular submicron dots determined using magnetic resonance force microscopy are in a good agreement with results obtained using conventional FMR and with theoretical descriptions.

Heusler-type magnetic shape memory alloys (MSMAs) exhibit a martensitic transformation (MT) accompanied by a complex magnetic reordering, strongly affected by an intricate martensitic microstructure. The hierarchic twin structure of martensite, formed as a result of minimization of elastic energy down to atomic scale, is under intensive study nowadays. On the other hand, the much more sophisticated problem of the relationship between nanoscale twin structure and the magnetism in MSMAs has being tackled only recently. It will be shown in this topical review that the nanotwin structure affects not only the basic magnetic parameters of MSMAs, but also can change qualitatively its magnetic nature and related magnetodynamic and magnetoresistance properties. This will be primarily illustrated, both theoretically and experimentally, on the prototype Ni-Mn-Ga and Ni(Co)-Mn-Sn MSMAs in the form of epitaxial thin lms, but the conclusions are also valid for other Heusler-type MSMAs, both in the form of thin lms, ribbons and bulk single crystals and polycrystals. The following new and remarkable phenomena will be highlighted. (i) A strong ferromagnetic exchange coupling is observed between the submicron twin components in Ni-Mn-Ga ferromagnetic martensite. It results in the modi cation of the average magnetic anisotropy and the formation of a non-collinear magnetic structure, whereby a negative magnetoresistance appears in a wide temperature range. (ii) Weak antiferromagnetic coupling occurs between the ferromagnetically ordered twin components in Ni(Co)-Mn-Sn martensite. This coupling enabled to explain the exchange bias and magnetic resonance spectra in the same terms as for arti cial antiferromagnetically coupled multilayered structures.