With varying thickness of the spacer near the second oscillatory GMR peak in Co/Cu system, a series of glass/Fe/[Co/Cu]20/Co multilayers are prepared by magnetronsputtering technique. The MR values are relatively small. High angle X-ray di raction shows that the copper crystallizes in fcc structure with (111) texture and the cobalt crystallizes in hcp structure with (002) preferential orientation. There is a mixed amorphous CoCu layer at the interface due to the di usion between cobalt and copper, which may decrease the MR value. The thickness, the mass density for each sub-layer and the surfacial and interfacial roughnesses are re ned from the X-ray specular reflectivity measurement.

We we have successfully fabricated ceramic superconductors of Hg-1223 with substitution of Pb for Hg, i. e. Hg1-xPbxBa2Ca2Cu3ov, by using encapsulation and short time annealing techniques. Samples fabricated in this manner may have nearly single phase structure and some enhancement ofTc can be achieved through this method. The materials of this ceramic with x ranging from 0 to 0.5 exhibit high-temperature superconductivity at temperatures falling in the range from 103 to 135K. The sample with optimum doping of Pb of x=0.34 and 6=0.40 has a highest Tc of 135K and its diamagnetic onset temperatureTdiac=143K. The composition of this sample has been found experimentally and is specified by a formula of Hg0.66Pb0.34Ba2Cal. 98Cu2.9708.4. The valence number for the copper constituent is given byvcu=2.30

HgBa2Ca2Cu3O81 d (Hg-1223) superconducting thin films of about 0.3mm in thickness have been successfully synthesized. The process involves depositing films (1mm thickness) of Ba2Ca2Cu3Ox on a SrTiO3 substrate by pulse laser ablation technique and implanting mercury ions into this deposited film, followed by annealing at oxygen atmosphere. The films so obtained show a relatively wide superconducting transition temperature up to 118K, as determined magnetically, which is similar to that of underdoping bulk Hg-1223.

Nd doped Y0.8 Ca0.2 Ba2-x Ndx Cu3 Oy YBNCO compounds with x≤.50 have been prepared by the solid state reaction technique. The structure and the superconductivity for YBNCO compounds are characterized. The zero resistance transition temperature T for each sample was measured. T increases with the increase of the content of Nd in YBNCO as xF0. 15, c0 c0 and decreases as xG0.20. X-ray diffraction studies show that there is no structural phase transition in the whole doping range. The dependencies of the lattice constants and some other structural parameters on the content of Nd for the samples YBNCO with xF0.20 have different behaviour than that for the samples with xG0.25. It seems that the uperconductivity of YBNCO is related to the structural changes due to Ca and Nd co-doping. q1999 Published by Elsevier Science B. V. All rights reserved.

The discovery of colossal magnetoresistance (CMR) 1 in thin film perovskite-like manganites has renewed interest in their possible use in device applications. 2 One of the crucial issues in thin film CMR manganites is the role of finite size effects related to structure on the thin film properties. Due to the restricted geometrical dimensionality of a thin film, a change in the layer thickness changes the metal-to-insulator transition temperature Tc. There exist several key areas for which we do not have a fundamental understanding of the physical processes that are occurring. Many of the problems arise from a poor understanding of the magnetism and structure at, or close to the interface region between the layer and the substrate.