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This letter presents theory and finite-difference time-domain calculations in excellent agreement with experiments for the transmission of a single subwavelength cylindrical hole in Ag metallic films. The authors discuss the very large enhancement in transmission by single holes in terms of surface plasmons at the interface of the hole. These are similar to the surface plasmons in metallic cylinders reported by Economou and co-workers [Phys. Rev. B 10, 3038 (1974); 24, 6908 (1981)]. The peak structures observed in experiments with arrays of holes are a consequence of interference of the beams transmitted by each hole and are determined by the hole periodicities. The role of the arrays in enhancement of the transmission due to surface plasmon polaritons appears to be marginal. [ABSTRACT FROM AUTHOR]

In this letter the authors show spin dependent transport experiments in nanoconstrictions ranging from 30 to 200 nm. These nanoconstrictions were fabricated by combined electron-beam lithography and thin film deposition techniques. Two types of geometries have been fabricated and investigated. They compare the experimental results with the theoretical estimation of the electrical resistance. Finally they show that the magnetoresistance for the different geometries does not scale with the resistance of the structure and obtain drops in voltage of 20 mV at 20 Oe. [ABSTRACT FROM AUTHOR]

We discuss the elastic coherent resistances of small contacts or constrictions between reservoirs. These resistances show an oscillatory behavior versus contact size, increase when the size of the contact decreases, and are dominant over the inelastic or residual resistances for realistic values of resistivities, temperature, and purity. [ABSTRACT FROM AUTHOR]

A new method to obtain information about local surface magnetic properties has been proposed recently. This new technique is based on the idea of measuring magnetic forces with a scanning tunneling force microscope. In this work we present a theoretical analysis of the relevant forces involved in magnetic force microscopy. Recent experiments with high-resolution images of laser-written domains in a magnetic thin film are discussed. [ABSTRACT FROM AUTHOR]

We present experimental evidence of the capability of the scanning tunneling microscope (STM) to image the microstructure of surfaces with atomic resolution even at atmospheric pressure. Some examples of different types of materials (metal single crystals, graphite, semiconductor, oxide and metal films) are shown. We propose the STM as a highly sensitive standard for surface roughness determination of industrial finishing at atmospheric pressure. In our opinion, these results may open new perspectives in technology and industrial applications. [ABSTRACT FROM AUTHOR]

Controlled size clusters of Au with a diameter of 13 Å, prepared using a multiple expansion cluster source, have been supported on highly oriented pyrolytic graphite and observed with a scanning tunneling microscope. A reliable constant-current signature for a metallic cluster supported on a graphite substrate is identified. Images of the supported Au clusters are found to exhibit a narrow size distribution and a diameter which is in close agreement with the diameter predicted from conditions in the multiple expansion cluster source. [ABSTRACT FROM AUTHOR]

This letter shows that conducting ballistic and tunneling magnetoresistances have identical physical treatments and, therefore, it is not possible to distinguish whether an experiment is measuring, in oxide barriers, electron conduction through pinholes or tunneling because both types of conduction are governed by the same physics. Currents in both cases are calculated by matching wave functions at the electrodes (both are ballistic). Therefore, pinholes or small ballistic nanocontacts in the tunnel barrier allow conducting ballistic electrons that account for most of the current. We also show that, in the case of nonsuperconducting materials, e.g., magnetic materials, current-voltage characteristics are not suitable to distinguish one process from the other. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

This letter shows that the ballistic magnetoresistance of Fe at room temperature and low magnetic fields is ten times smaller than for Ni and Co. The results are well explained by theory that provides a global understanding for 3d transition metals because, for Fe, the ratio of majority to minority spins at Fermi level is much smaller than for Ni and Co. The data indicate that conduction is carried out by majority d electrons in the case of Fe, in contrast to what happens for Ni and Co. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Using the finite-difference time-domain method, we theoretically study elastic waves propagating in a two-dimensional composite consisting of aluminum cylinders embedded in mercury. The importance of the transverse components of the aluminum scatterers in the creation of the gaps is shown by switching off the transverse waves inside the aluminum. In that case, there are very narrow gaps or no gaps at all. In contrast, when the transverse components are on, as they should be, wide full band gaps appear for longitudinal incident waves. Since mercury supports only longitudinal waves, these are full elastic band gaps. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]