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The layer structure of a series of Fe/Au multilayers has been studied by grazing incidence specular and diffuse X-ray scattering. In particular, the evolution of the layer and interface characteristics has been followed as a function of the number of bilayers grown. Torque magnetometry measurements showed that the easy axis of magnetization of all samples lay in the film plane, the effective anisotropy constant per unit volume remaining constant as the bilayer number increased. These data contrast with previous studies showing that Fe/Au multilayers exhibited perpendicular anisotropy when the Fe layer is thinner than 10 Å. Fitting of model structures to the grazing incidence specular and diffuse X-ray scattering data showed that the r.m.s. roughness was high, being between 10 and 20 Å for different samples within the series. There was no systematic trend in the amplitude as a function of bilayer repeat number but the in-plane length scale of the roughness increased with layer thickness. The fractal parameter h fell linearly with bilayer repeat number. We suggest that the high level of roughness results in the in-plane anisotropy in these layers. A superlattice sample with 100 bilayers displayed a significantly lower roughness of 8 (±0.3) Å and perpendicular anisotropy. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

We present transient ellipsometry measurements made upon Au, Cu, Ag, Ni, Pd, Ti, Zr, and Hf thin films under identical experimental conditions. Using an elliptically polarized pump beam, we have simultaneously observed the specular inverse Faraday effect (SIFE) and specular optical Kerr effect (SOKE) contributions to the optical polarization response, in order to extract the real and imaginary parts of the non-vanishing components of the third-order optical susceptibility tensor. The signal magnitudes and the extracted tensor components show a systematic variation that reflects the underlying band structure of the different metals. A time delay observed between the SIFE and SOKE signals is interpreted in terms of lifetimes for the transient polarization that may be of comparable magnitude to the pulse width. This suggests that formulae derived in the continuous wave limit may not be applicable in the description of ultrafast nonlinearities in metallic samples. The implications of our results for different areas of applied optics are discussed.

We present transient ellipsometry measurements made upon Au, Cu, Ag, Ni, Pd, Ti, Zr, and Hf thin films under identical experimental conditions. Using an elliptically polarized pump beam, we have simultaneously observed the specular inverse Faraday effect (SIFE) and specular optical Kerr effect (SOKE) contributions to the optical polarization response, in order to extract the real and imaginary parts of the non-vanishing components of the third-order optical susceptibility tensor. The signal magnitudes and the extracted tensor components show a systematic variation that reflects the underlying band structure of the different metals. A time delay observed between the SIFE and SOKE signals is interpreted in terms of lifetimes for the transient polarization that may be of comparable magnitude to the pulse width. This suggests that formulae derived in the continuous wave limit may not be applicable in the description of ultrafast nonlinearities in metallic samples. The implications of our results for different areas of applied optics are discussed.

A novel hybrid organic/inorganic heterostructure is described, comprising a highly ordered discotic liquid crystal layer, self-organised on an ultrathin Au film. The electronic properties of the hybrid structure have been investigated using a range of theoretical techniques. The strong bonding of the molecules onto the metal surface, combined with the high degree of periodicity across the molecular layer, results in the formation of a hybrid metal/molecular band structure which has been calculated using a periodic Newns-Anderson model. The in-plane conductivity was calculated using the Kubo-Greenwood formula, and electron trapping in the molecular layer was considered by use of a diffusion model. The effect of trapping is apparent in the frequency domain conductivity. The sensitivity of the frequency domain response to variations in the trapping parameters was studied, and interpreted in terms of potential gas sensing functionality.

The electronic conductivity, diffusion coefficient and the self-energy in the vicinity of the energy gap of amorphous Si at T=0K have been computed as a function of energy for a fully bonded model of Si. We have used the equation-of-motion method in κ-space to show, for the first time, the probable position and existence of mobility edges. The conductivity rises rapidly away from the mobility edges to take values typical of those found in liquid metals. The behaviour of the self-energy indicates that a resonance phenomenon is responsible for the formation of a gap.