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The effect of the oxygenation process on the microstructural and superconducting properties of melt-textured YBa2Cu3Oy/Y2BaCuO5 bulk composites was investigated. Specifically, it was shown that short oxygenation periods lead to oxygen-deficient, dark bands parallel to the a-b planes while long oxygenation periods gives rise to an aging process. Both extremes degrade the critical currents and irreversibility lines of the composite superconductors.

The use of very small amounts of CeO2 additives for attaining the directional solidification of YBa2Cu3O7 superconductors is described. The technique enhances the critical current density of YBa2Cu3O7/Y2BaCuO5 ceramic composites through a decrease in the size of the mean Y2BaCuO5 precipitates. To date, it has been applied to 'long single domain bars' of YBa2Cu3O7 superconductors.

Bulk YBa2Cu3O7 superconductors fabricated via the melt-textured process have been used as material in an inductive fault current limiter developed as part of the MIDAS program. The device, which is based on a transformer topology, has been tested by way of short-circuiting the load and other measurements. The experimental results showed good agreement with simulations although the quench predictions contained room for improvements.

An experiment to evaluate the magnetic flux and microstructural characteristics of YBa2Cu3O7 ceramic superconductors was performed. It involved the fabrication of melt-textured ceramics for measurements via a mutual inductance microprobe. This measuring instrument was specially developed for characterizing the weak links of the high-angle grain boundaries. It also facilitated an examination of flux penetration and trapping in a specimen at 25 K.

The magnetic and electronic properties of Eu2Ru2O7 are discussed in terms of the local ruthenium and europium coordination, electronic band structure calculations, and molecular orbital energy levels. A preliminary electronic structure was calculated within the local density approximation (LDA) and local spin density approximation taking in to account on-site Hubbard U (LSDA+U). The molecular orbital energy level diagrams have been used to interpret the Eu-Ru ligand spectrum and the ensuing magnetic properties. The orbital hybridizations and bonds are discussed. [ABSTRACT FROM AUTHOR]

Various experiments are conducted to analyze the influence of the crystallographic shear planes on the magnetic and superconducting behavior in the bulk sample of Ru[Sr.sub.2]Eu[Cu.sub.2][O.sub.8]. The results prove that these shear planes are mainly responsible for producing the anomalies in the samples.

AC losses in a superconducting transformer are measured and reported.

For the concentration, ferromagnetic (FM) transition is already extremely board and the relation of this behavior with structural disorder and possible phase separation is discussed. A comparison of the experimental results in the PM regime with reported data on the ordered phase indicates a complex magnetic behavior associated with Y substitution.

The magnetic behavior of a series of Tl(sub 2)Mn(sub 2-x)Ru(sub x)O(sub 7) samples was explored as a function of field and temperature. The substitution of Mn ions by Ru ions produced a strong change of both magnetic and transport properties. The magnetic frustration progressively increased, which signalled the increase of antiferromagnetic interactions and the geometrical frustration intrinsic to the pyrochlore structure.

Magnetization measurements on grain-aligned Re-doped Hg-1223 superconductor have been performed. The anisotropic magnetic hysteresis M irr is analyzed as a function of temperature and magnetic field, and the irreversibility line H irr(T) is determined. Both M irr and H irr(T) show similar values along the main crystallographic directions, indicating a marked fall in superconducting anisotropy because of Re substitution.

Electron spin resonance (ESR) and dc susceptibility, Xdc(T) measurements were performed in the perovskite La(sub0.7)Ca(sub0.3)MnO(sub3) up to 1000 K. The ESR intensity follows a T dependence of Xdc(T). It is concluded that the relaxation mechanism is virtually the same for the entire studied paramagnetic range. A similar T dependence has been found for other perovskites and the pyrochlore In(sub2)Mn(sub2)O(sub7).

The magnetoresistance and magnetization of ceramic La(sub2/3)A(sub1/3)MnO(sub3) oxides were studied as a function of the grain size. The ceramics become harder magnetically when the particle size is reduced, showing a large magnetic anisotropy, rising with reduced grain size. A gradual increase of the low-field magnetoresistance is also observed. Both phenomena are thought to be closely linked and related to the existence of spin disorder at the grain boundaries.

Strain-induced self-assembled La0.7Sr0.3MnO3 nanoislands of lateral size 50-150 nm and height 10-40 nm have been grown on yttria-stabilized zirconia (001)-substrates from ultradiluted chemical solutions based on metal propionates. The nanoislands grow highly relaxed withstanding the epitaxial relation (001)LSMO[110]//(001)YSZ[010] and show bulk-like average magnetic properties in terms of Curie temperature and saturation magnetization. The interplay of the magnetocrystalline and shape anisotropy within the nanoisland ensemble results in an in-plane magnetic anisotropy with a magnetocrystalline constant K1(150 K)=-(5±1) kJ/m3 and in-plane easy axis along the [110]-La0.7Sr0.3MnO3 direction as measured, for the first time, through ferromagnetic resonance experiments. Magnetic force microscopy studies reveal the correlation between nanoisland size and its magnetic domain structure in agreement with micromagnetic simulations. In particular, we have established the required geometric conditions for single domain, multidomain, and vortex configurations. [ABSTRACT FROM AUTHOR]

The impact of high-temperature creep under varying conditions in melt-textured YBa2Cu3O7-Y2BaCuO5 composites, with high critical currents before deformation is studied. The low-temperature oxygenation process is observed to produce a strong modification of the as-deformed microstructure and to cause a clear degradation of the superconducting capabilities. This behavior of the superconducting characteristics is related to the formation of extended planar defects such as large stacking faults and microcracks that severely reduce the vortex cutting length.