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Cesium treatment lowers the threshold field for field emission and increases the emission site density from a nominally n-type diamondlike carbon film which is deposited using an rf plasma of methane and nitrogen gases. The treatment involved the deposition of cesium followed by a low temperature anneal. Dramatic improvements to field emission by cesiation cannot be generalized to all diamondlike samples as similar treatment of a type llb single-crystal diamond did not produce as pronounced an improvement in turn-on field or emission site density.

Square arrays of circular pinning centers of various diameters were patterned in Nb thin films to explore their vortex pinning behavior. Periodic critical current matching peaks and some 'missing peaks' were observed in magnetotransport measurements. The larger the diameter of the pinning centers, the higher the index of the missing matching fields observed. This phenomenon is explained by molecular dynamics simulations and is caused by the interaction between interstitial vortices and vortices occupying the pinning centers. [ABSTRACT FROM AUTHOR]

The vortex propagation exhibits rectification effect in Nb superconductors with spacing-graded density of holes. A rectified dc voltage is obtained when the vortex lattice is driven by ac current. The asymmetric geometry of the pinning array produces a significant influence on the vortex motion. The rectified voltage depends considerably on the amplitude of the applied ac current and the magnetic field. The experimental results reveal a drastic change of the vortex rectification for magnetic field above/below the first matching field. The reason may be that the interstitial vortices are formed in the film above the first matching field. A reversible vortex motion is induced by the interstitial vortices for the field above the first matching field. [ABSTRACT FROM AUTHOR]

Several magnetotransport measurements are conducted to determine the special pinning phenomena that is exhibited by the different superconductors with regular composite pinning arrays. The positions of the matching peak are shown to be extremely irregular.

The effective spin-mixing conductance in [Ni.sub.80][Fe.sub.20]/Pt is examined by measuring the interface-induced enhancement of the Gilbert damping constant. The studies have shown the nonlinear behavior of the effective spin-mixing conductance and have suggested that the nonlinear spin wave modes excited at high incident microwave power are detrimental to the spin pumping effect.

Electron-beam lithography and reaction dry etching methods are used for fabricating superconductor thin films with regular square hole arrays to explore the vortex pinning behavior. Novel pinning phenomenon is found in the magnetoresistance measurements of all the samples and it is related to the multivortex states.

Microwave assisted magnetization switching is examined by using [Fe.sub.30][Co.sub.70]/[Al.sub.2][O.sub.3]/[Ni.sub.80][Fe.sub.20] magnetic tunnel junctions incorporated with a coplanar waveguide. The results have shown that microwave is an efficient mean to switch the magnetization of a thin film.

In this study, the effective spin-mixing conductance in Ni80Fe20/Pt was investigated by measuring the interface-induced enhancement of the Gilbert damping constant. Ferromagnetic resonance spectra were measured in coplanar waveguide geometry with different incident microwave powers. The nonlinear behavior of normal Gilbert damping G0 and effective spin-mixing conductance g↑↓ have been observed when the incident microwave power is above a critical ac field hrf of 1.6 Oe. Both phenomena are explained by considering the coupling between spin coherent precession and spin wave modes. This work demonstrates the nonlinear behavior of the effective spin-mixing conductance g↑↓. It suggests that the nonlinear spin wave modes excited at high incident microwave power are detrimental to the spin pumping effect and should be avoided in future spin battery designs. The capability of tuning G0 and g↑↓ through the microwave power is also useful for the fundamental study on the damping mechanism. [ABSTRACT FROM AUTHOR]

The vortex propagation has been investigated in Nb superconductors with one dimension spacing-graded density of submicrometer-scaled holes in this research. A rectification effect can be discerned because the applied ac is transformed into a net dc voltage. These results demonstrate that the rectification is mainly characterized by the asymmetric pinning landscape and the rectified voltage depends considerably on temperature and the amplitude of applied ac. The dc voltage increases steeply up to the maximum value and then decreases to zero dc voltage with the increase of ac. The shape of peaks in the dc voltage signal become steeper and move to higher applied ac regime with the decrease of temperature. [ABSTRACT FROM AUTHOR]