We study the magnetic properties of nanoscale magnetic films with large perpendicular anisotropy comparing polarization microscopy measurements on Co28Pt72 alloy samples based on the magneto-optical Kerr effect with Monte Carlo simulations of a corresponding micromagnetic model. In our model the magnetic film is described in terms of single-domain magnetic grains, interacting via exchange as well as via dipolar forces. Additionally, the model contains an energy barrier which has to be overcome in order to reverse a single cell and a coupling to an external magnetic field. Disorder is taken into account.We focus on the understanding of the dynamics especially the temperature and field dependence of the magnetisation reversal process. The experimental and simulational results for hysteresis, the reversal mechanism, domain configurations during the reversal, and the time dependence of the magnetisation are in very good qualitative agreement. The results for the field and temperature dependence of the domain wall velocity suggest that for thin films the hysteresis can be described as a depinning transition of the domain walls rounded by thermal activation for finite temperatures. 75.60.Ch, 75.60.Ej, 75.40.Mg

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SummaryScanning near-field optical microscopes (SNOM) using the tetrahedral-tip (T-tip) with scanning tunnelling microscopy (STM) distance control have been realized in transmission and reflection mode. Both set-ups used ordinary STM current-to-voltage converters allowing measurement of metallic samples. In the transmission mode, a resolution of 10 nm to 1 nm with regard to material contrast can be achieved on binary metal samples. Because of the great near-field optical potential of the T-tip with respect to the optical resolution, it is a challenging task to find out whether these results can be transferred to non-metallic sample systems as well. This paper reports on a newly designed SNOM/STM transmission mode set-up using the tetrahedral-tip. It implements a sensitive current-to-voltage converter to widen the field of measurable sample systems. Beyond this, mechanical and optical measuring conditions are substantially improved compared to previous set-ups. The new set-up provides a basis for the routine investigation of metal nanostructures and adsorbed organic monolayers at resolutions in the 10 nm range.

Monolayers of monodisperse latex beads of submicron size are used as a convenient mask for physical vapour deposition to produce latex bead projection patterns as nanostructures that have been used often as test structures for near-field optical applications. Variations of the fabrication technique lead to derived nanostructures: flat surface structures are formed by embedding projection patterns consisting of one material into the surface of a different material; complementary projection patterns are formed by using a projection pattern as a mask for a nanoimprinting process; and submicron ring structures are formed in a controlled way from the debris of the latex bead mask. The application of such nanostructures as test patterns for scanning near-field optical microscopy (SNOM) is demonstrated.

Thin multilayers of a negatively charged cyanine dye and a positively charged polyelectrolyte were deposited onto a thin, partially transparent film of gold, initially covered by a self-assembled monolayer of cystamine. Transmission spectra of the multilayers have an antisymmetric shape with a dip and a peak in the transmission. Unlike the transmission spectra of the same dye on a transparent glass support, the spectra reflect the shape of the real part of the dielectric function of the dye layer. At the peak the transmission exceeds the transmission of the uncovered gold film by a factor of up to 2.5.