We have prepared the Y Ca Ba Cu O with xF compounds by the solid state reaction technique. The uperconduct-1yx x 2 3 y ing critical temperature was measured. The structural parameters as a function of Ca substitution were obtained through the detailed analysis of the X-ray diffraction for these Ca-doped samples. The variation of the lattice parameters, some meaningful bond lengths, and the microstrain in lattice change with the Ca content have been discussed.

Lai. 85Sro. 15Cul-yMy04 ceramic cuprates with M-Zn, Ni, Mg, and). ≤0.30 have been synthesized. The superconduct-ing critical temperatures and the room temperature resistivities for M doping have been determined by a standard four-probemethod. The width of each reflection of X-ray diffraction for each sample is analyzed by Rietveld refinements which is related to the average grain size and the average lattice microstrain. In this way we attempt to explain the stronger suppression for non-magnetic doping such aS Zn or Mg than that for magnetic doping such as Ni.

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

Si/Ta/Co/Cu/CoFeMn sor NiOd spin valves were prepared by a delayed sputtering procedure, in which depositions of Ta and followed layers were intervened by 1 h. The spin valves are found to have better coherent growth with stronger s111d preferred orientations in Co and Cu layers, compared with the traditional continuous method. At the same time, the giant magnetoresistance ratio and spin-dependent scattering are enhanced by a factor of 20%-30%. These results indicate that the coherent growth and the s111d preferred orientation can enhance the spin-dependent scattering of spin valves.

The magnetic and electrical properties of crystalline Mn0.05Si0.95 films prepared by post-thermal treatment of the as-deposited amorphous Si-Mn s95 at.%−5 at.%d have been investigated. Both the temperature dependence and field dependence of magnetization were measured using superconducting quantum interference devices, and it has been indicated that the film materials are ferromagnetic with Curie temperature over 400K. X-ray diffraction analysis revealed full crystallization of the films and the incorporation of Mn into the host crystalline Si lattice. Behavior of thermally activated conduction processes of the films has been evinced by electrical property measurement for the films.

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.

Crystal tilts in the epitaxial lateral overgrown (ELO) GaN region over SiO2 mask by hydride vapor phase epitaxial away from the opening region were investigated by scanning electron microscope and the four-circle x-ray diffraction method. The increased mask width and ratio of stripe opening width to stripe period (fill factor) lead to increased wing tilts. The introduction of additional HCl and C3H8 /H2 can decrease wing tilts and improve the ELO GaN surface morphologies significantly. Moreover, it has been observed that a high growth rate will bring more defects and large wing tilts into the GaN materials.

Modulation-doped Al0.22Ga0.78N/GaN heterostructure with 1000 A Si-doped n-Al0.22Ga0.78N barrier (n-AlGaN) were deposited on (0001)-oriented sapphire (-Al2O3) by means of atmosphere-pressure metal-organic chemical vapor deposition. The reciprocal space mappings of symmetric reflection (0002) and asymmetric reflection (1014) were measured with high resolution X-ray diffraction. The results indicate that the microstructure and strain status of barrier correlate to that of the underlying i-GaN layer. The barrier holds an "abnormal" strainrelaxation status, which probably results from the internal defects of n-AlGaN and the strain relaxation status at the i-GaN/-Al2O3 interfaces. The results from grazing incidence X-ray diffraction show that the strain in barrier is nonuniform, which is consistent with the results from the reciprocal space mappings.

Cations of Y and Sr co-substituting for La and Ca at A site in La2/3Ca1/3MnO3 compound, a2/3−xYxCa1/3−ySryMnO3, were synthesized successfully by solid-state reaction. X-ray diffraction shows there is only one phase with the dopants of Y and Sr within x≤0.20 or y≤0.19. The lattice parameters along a-, b-, and c-direction remain almost unchanged with x≤0.20. The bond angle of Mn O Mn ncreases from 151.9 for x=0 to 172.7 for x = 0.20 monotonically, which indicates that the Jahn-Teller effect in MnO6 octahedron decreases with increasing x. The temperature dependence of resistance with/without magnetic applied were measured and fitted theoretically. The metal-to-insulator transition emperature, TMI, decreases with increasing the Y content with x≤0.10 while TMI increases slightly with further increasing x. The Y-content dependence of magnetoresistance shows a parabolic behavior. The maximum MR value corresponds to x=0.08-0.10.We attributed these variations in the structure and transportation to the cation disorder due to the cation doping.

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.