Magnetic multilayer structures of Co/Cu prepared by dc magnetron sputtering are studied with respect to changing number of bilayers (N) for different thicknesses of the Cu spacer layer corresponding to different coupling conditions according to the oscillatory interlayer exchange coupling. X-ray reflectivity and diffuse scattering show that the multilayers become smoother with increasing N. The growth exponent of the roughness is found to be lower for a multilayer than for a single-layer film of similar thickness. The roughness of subsequent interfaces along the stack is conformal, and the lateral correlation does not change with the period number, but depends on the thickness of the spacer layers. The improved layer structure for larger N increases the antiferromagnetic coupling fraction as inferred from magneto-optic Kerr effect measurements and thereby increases the giant magnetoresistance (GMR) ratio up to 35% for N = 10. Thus, the first few bilayers do not contribute to the GMR but act as a buffer to improve the growth conditions for the following bilayers. The first about five bilayers can be replaced by a bottom Co layer of equivalent thickness which also improves the layer structure for a subsequently deposited lower number of bilayers without much loss in the GMR ratio. This smoothening effect due to the increasing of the thickness of the bottom-most layer is related to the simultaneously decreasing grain size.

No abstract

Articles you may be interested inEffects of grain cluster size on coercivity and giant magnetoresistance of NiFe/Cu/CoFe/Cu/NiFe pseudo spin valves Appl.

The effect of oxygen enrichment to the atomization air is examined here in a twin-uid atomizer. A commercially available solid-cone, air-assist atomizer was used in which the atomization airstream was enriched to contain a volume fraction of 35 and 45% oxygen in nitrogen. The results are compared with the baseline case of 21% O 2 because air is the most commonly used mode of operation for twin-uid atomizers. Data were obtained on droplet size, number density, and velocity at several spatial locations in the spray ames using a two-component phase Doppler interferometer. The global features of the spray ames, recorded photographically, were affected dramatically by oxygen enrichment of the atomizationair. Speci cally, the ame luminosity increases, and the ame height and volume decreases with an increase in oxygen concentration supplied to the atomization air. A moderate increase in oxygen concentration produced a whitish color high-temperature violent combustion zone near the nozzle exit. In addition, ames with oxygen-enriched atomization air reduced the number of unburned droplets escaping the ame plume into the surrounding environment. This observation was supported by the phase Doppler measurements in which droplet mean size and velocity increased and droplet number density decreased as a result of enhanced droplet vaporization. The results suggest that oxygen enrichment of the atomization air provides a signi cant improvement to the initial mixing between the reactants immediately downstream of the nozzle exit. This improvement, in turn, in uences droplet vaporizationand transport, ame stability, and combustion intensity.

No abstract