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Notes: Boron nitride films prepared by reactive ion plating from a boron evaporation source were characterized structurally using three independent electron optical techniques: energy filtered electron diffraction with radial distribution function analysis; electron energy-loss spectroscopy of the near-edge structure of the boron K edge; and spectroscopy of the plasmon region of the energy-loss spectrum. Both specimens had a graded BNx layer between the BN layer and the silicon substrate and in addition one specimen had a titanium bonding layer underneath the BNx layer. The presence of c-BN in both specimens was confirmed by all techniques. The specimen with the titanium bonding layer was examined in cross section and showed essentially pure c-BN on the surface. A model for the formation of c-BN assisted by the compressive stress generated during deposition is proposed.

Notes: A magneto-optic imaging technique was used to examine the flux distributions at 50, 60, and 70 K in a single-crystal platelet of YBa2Cu3O7. The superconducting sample was covered with a layer of iron garnet film, and a polarization microscope was used to examine the magnetic domains in this imaging film. Since the spacing of these domains was proportional to the local magnetic field in the underlying superconductor, it was possible to determine field profiles directly from the optical density of the image. Field profiles indicated that the distributions of remnant flux in the sample were well described by the critical state model. It was also possible, through the use of simple linear models of initial flux penetration, to measure the flux trapped in the sample as a function of time. The flux creep data derived from analysis of the digitized images showed a logarithmic decrease of magnetization with time, in good agreement with SQUID magnetometer measurements performed on the sample. There was no evidence of an axial critical state.

Notes: An illuminated cuprous oxide-covered electrode immersed in alkaline media exhibits a nonlinear dependence of photocurrent on the intensity of 488 nm laser illumination. Results from intensity modulation experiments show that the differential efficiency for converting photons to photocurrent in the p-type cuprous oxide thin film is inversely proportional to the square root of illumination intensity. A charge transfer model that includes intensity dependent optical absorption in the cuprous oxide layer is found to be consistent with the observed photocurrent response. Analysis of the experimental results using the charge transfer model shows that the saturation intensity for cuprous oxide is approximately 100 mW/cm.2 Photoelectrochemical charge transfer is found to be efficient in the potential region where the nonlinear photocurrent response is observed, with nearly all photoinjected minority carriers being consumed by the interfacial charge transfer reaction rather than by recombination.

Notes: We have developed an experimental method for investigating the interaction between two dc track edges by studying the track edge noise. We conclude that two edges do not interact when they are several micrometers apart, but the noise reduces nearly to zero when their separation is less than about half a micrometer. There is a transition region that exists between these two limits. The net track edge noise power from two dc edges is quantized, implying that in our experiment track edges interact around the complete revolution of the disk or not at all.

Notes: Co/Ru hcp (0001) superlattices were grown by UHV evaporation onto mica substrates. We demonstrate the growth of epitaxially ordered Co/Ru superlattices–despite the large lattice mismatch ((approximately-equal-to)8%)–consisting of hcp (0001) Co and Ru sublayers initialized on 150-A(ring)-thick single-crystalline Ru buffer layer by using RHEED and x-ray diffraction. The magnetic properties were studied by magnetization and ferromagnetic resonance (FMR) measurements. For uncoupled Co layers, the resultant anisotropy switch from planar to axial direction (perpendicular to the film plane) with decreasing Co sublayers thickness. For Co sublayer thickness smaller than a critical one tco(approximately-equal-to)14 A(ring), the magnetization is directed perpendicular to the film plane. For small Ru interlayer thickness, large antiferromagnetic exchange coupling between the Co sublayers is observed in agreement with precious results. For a certain range of Co and Ru thicknesses, superlattices with unique magnetic parameters are obtained. Indeed, in the absence of an applied field, the magnetization is oriented along the film normal while the adjacent Co layers are coupled antiferromagnetically. For this magnetic structure, the magnetization process exhibits a hysteresis and the FMR spectra an irreversible behavior when the applied field is along the film normal.As shown by SQUID measurements, when the field is decreased from a quasi-saturated state, the layers are essentially coupled ferromagnetically, the antiferromagnetic state appearing following a spin-flip process (staircaselike on the magnetization curve) for a field smaller than a critical one. However, with increasing field, the antiferromagnetic state disappears by progressive steps suggesting that the spin reorientation process occurs by coherent rotation of the magnetization combined with spin-flip process. The occurrence of this effect is particularly spectacular on the FMR spectra. With decreasing field, a classical FMR absorption is observed due to the basical ferromagnetic state while with increasing field, this absorption is largely reduced or disappears completely due to the antiferromagnetic one. The magnitude of the hysteresis and its evolution with the direction of the applied field, the values of the critical field corresponding to the spin flip and to the field above which the magnetic state is reversible, are very well correlated on the FMR spectra and the magnetization curves.