Mixed conducting yttrium-barium-cobalt-oxide for high oxygen permeation

Yttrium-barium-cobalt-oxide (YBC), especially with low Y content, has been prepared. Oxygen permeation in these materials is very high at moderate temperature. The materials Y0.05BaCo0.95O3-δ and Y0.10Ba0.90CoO3-δ consisted of a BaCoO3-δ like main phase and some minor phases. For the Y0.05BaCo0.95O3-δ material these minor phases were not exceeding 10 vol%. Y0.05BaCo0.95O3-δ had the highest oxygen permeation value of 3.9 × 10-7 mol/cm2s at 900°C; the surface exchange reaction may be the rate limiting step here. The material Y0.33Ba0.67CoO3-δ consisted mainly of two unknown cubic phases.\u

Home-grown CASE tools with XML and XSLT

This paper demonstrates an approach to software generation where xml representations of models are transformed to implementations by XSLT style sheets. Although XSLT was not primarily intended for this use, it serves quite well. There are only few problems in this approach, and we identify these based on our examples

Conductance anisotropy and linear magnetoresistance in La2-xSrxCuO4 thin films

We have performed a detailed study of conductance anisotropy and magnetoresistance (MR) of La2-xSrxCuO4 (LSCO) thin films (0.10 < x < 0.25). These two observables are promising for the detection of stripes. Subtle features of the conductance anisotropy are revealed by measuring the transverse resistance Rxy in zero magnetic field. It is demonstrated that the sign of Rxy depends on the orientation of the LSCO Hall bar with respect to the terrace structure of the substrate. Unit-cell-high substrate step edges must therefore be a dominant nucleation source for antiphase boundaries during film growth. We show that the measurement of Rxy is sensitive enough to detect the cubic-tetragonal phase transition of the SrTiO3(100) (STO) substrate at 105 K. The MR of LSCO thin films shows for 0.10 < x < 0.25 a non-monotonic temperature dependence, resulting from the onset of a linear term in the MR above 90 K. We show that the linear MR scales with the absolute Hall resistivity, with the constant of proportionality independent of temperature. Such scaling suggests that the linear MR originates from current distortions induced by structural or electronic inhomogeneities. The possible role of stripes for both the MR and the conductance anisotropy is discussed throughout the paper

Superconducting Mg-B films by pulsed laser deposition in an in-situ two-step process using multi-component targets

Superconducting thin films have been prepared in a two-step in-situ process, using the Mg-B plasma generated by pulsed laser ablation. The target was composed of a mixture of Mg and MgB2 powders to compensate for the volatility of Mg and therefore to ensure a high Mg content in the film. The films were deposited at temperatures ranging from room temperature to 300 degrees C followed by a low-pressure in-situ annealing procedure. Various substrates have been used and diverse ways to increase the Mg content into the film were applied. The films show a sharp transition in the resistance and have a zero resistance transition temperature of 22-24 K.Comment: 4 pages, 3 figures, submitted to Applied Physics Letter

Experimental realization of SQUIDs with topological insulator junctions

We demonstrate topological insulator (Bi$_2$Te$_3$) dc SQUIDs, based on superconducting Nb leads coupled to nano-fabricated Nb-Bi$_2$Te$_3$-Nb Josephson junctions. The high reproducibility and controllability of the fabrication process allows the creation of dc SQUIDs with parameters that are in agreement with design values. Clear critical current modulation of both the junctions and the SQUID with applied magnetic fields have been observed. We show that the SQUIDs have a periodicity in the voltage-flux characteristic of $\Phi_0$, of relevance to the ongoing pursuit of realizing interferometers for the detection of Majorana fermions in superconductor- topological insulator structures