Ik Schuller

Structural phase transition in YBa2Cu3O7−δ: the role of dimensionality for high temperature superconductivity

Abstract We have performed detailed high temperature X-ray diffraction to study the nature of the structural phase of YBa 2 Cu 3 O 7− δ . The results indicate the existence of a reversible orthorhombic to tetragonal phase transition at a temperature close to 750°C. If the high temperature tetragonal phase is quenched-in at low temperatures the critical superconducting temperature is considerably reduced from 92.5 K. This suggests that the one dimensional CuO chains present in the orthorhombic structure are necessary for high temperature superconductivity.

Solubility and superconductivity in RE(Ba2-xREx)Cu3O7+δ systems (RE=Nd, Sm, Eu, Gd, Dy)

Solid solutions of RE(Ba2-xREx)Cu3O7+ delta (RE=Nd, Sm, Eu, Gd, Dy) for x=0 to x=0.5 have been investigated. X-ray and resistivity measurements show that there exists a solid solution region, through which the structure changes from orthorhombic to tetragonal and the superconducting properties are depressed. The solubility limits depend strongly on the size of the rare-earth ion, with the smallest (Dy) showing no appreciable solubility. The superconducting transition temperature versus x for all of the rare-earth-ion substitutions falls on a universal curve, indicating that the Ba sites are extremely ionic and magnetically isolated.

Phase diagram and oxygen stoichiometry of Y‐Ba‐Cu‐O thin films

We have performed an exhaustive study of the phase diagram of Y‐Ba‐Cu‐O thin films using chemical analysis, energy dispersive x‐ray spectroscopy, Auger electron spectroscopy, and x‐ray diffraction. We show that Raman scattering can provide information regarding impurity phases and oxygen stoichiometry in thin films

Angular dependence and origin of asymmetric magnetization reversal in exchange-biased Fe / FeF 2 ( 110 )

The asymmetry of the magnetization reversal process in exchange biased Fe/FeF

Oxygen Bonding in High-Temperature Superconductors

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Low-angle X-ray diffraction of multilayered structures

has been studied by magneto-optical Kerr effect. Qualitatively different transverse magnetization loops are observed for different directions of the cooling and the measuring field. These loops can be simulated by a simple calculation of the total energy density which includes the relevant magnetic anisotropies and coherent magnetization rotation only. Asymmetric magnetization reversal is shown to originate from the unidirectional anisotropy and may be observed if the external measuring field is not collinear with either the exchange bias or the easy axis of the antiferromagnetic epitaxial FeF

Lattice mismatch and interfacial disorder in superlattices

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Oxygen Ordering and Superconducting Phases in Ceramics

(110) layer.

Influence of the interface on the crystallization of amorphous Ge in Pb/Ge multilayers

Oxygen evolution experiments in low- and high-Tc ceramic superconductors are used to identify the desorption kinetics and activation energies. It is found that oxygen desorps at 600 °C from Cu-O chains (where present) with an activation energy of 1.2 eV, whereas the desorption from other oxygen-containing planes occurs at 800 °C with a higher activation energy of 2.8 eV.

Nature of coupling and dimensional crossover in superconducting multilayers

Low-angle X-ray diffraction profiles can provide detailed information about the multilayer periodicity and thickness of the individual layers that make up a multilayer. The effect of discrete and continuous random cumulative fluctuations of the layer thicknesses on the diffraction profiles of single films, bilayers and multilayers is discussed. It is shown that the calculated low-angle profiles of single films can distinguish between discrete and continuous thickness errors. In bilayers and multilayers, however, no difference between these thickness errors can be seen and only an overall thickness error may be extracted.