R. J. Soulen

A contactless method for measurement of the critical current density and critical temperature of superconducting films

A new method is described for measuring the critical current density and transition temperature of a superconducting film without making contact to it or modifying it in any way. This technique is particularly well suited for use with high transition temperature oxide films which are notoriously irreproducible and sensitive to patterning. It consists of positioning a flat, multiturn coil near the film surface and driving the coil with an audio frequency sine‐wave current. Induced shielding currents flow in the film. We have calculated the radial dependence of the induced currents and show that the induced current density is zero at the coil center, rises to a maximum near the mean radius of the drive coil, and then falls off rapidly as the radius continues to increase. A measurement of the critical current per length can be obtained by monitoring the development of odd harmonic voltage components across the coil as the drive current is increased. We find that this measure of nonlinearity in the coil–film ...

Origin of high transport spin polarization in La 0.7 Sr 0.3 MnO 3 : Direct evidence for minority spin states

Using the point-contact Andreev reflection technique, we have carried out a systematic study of the spin polarization in the colossal magnetoresistive manganite,

Analysis of point-contact Andreev reflection spectra in spin polarization measurements

{\mathrm{La}}_{0.7}{\mathrm{Sr}}_{0.3}{\mathrm{MnO}}_{3}

Transport spin polarization of Ni_{x}Fe_{1-x}: Electronic kinematics and band structure

(LSMO). Surprisingly, we observed a significant increase in the current spin polarization with the residual resistivity. This counterintuitive trend can be understood as a transition from ballistic to diffusive transport in the contact. Our results strongly suggest that LSMO does have minority spin states at the Fermi level. However, since its current spin polarization is much higher than that of the density of states, this material can mimic the behavior of a true half-metal in transport experiments. Based on our results we call this material a transport half-metal.

Fabrication of YBa2Cu3O7−δ/SrTiO3/La0.7Sr0.3MnO3−δ junctions for the control of supercurrent by spin-polarized quasiparticle current injection

We present a systematic analysis of point-contact Andreev reflection (PCAR) spectra for ferromagnetic materials, using both modeling and experimental data. We emphasize the importance of consistent data analysis to avoid possible misinterpretation of the data. We consider the relationship between ballistic and diffusive transport, the effect of different transport regimes on spin polarization measurements, and the importance of unambiguous identification of the type of transport regime. We find that in a realistic parameter range, the analysis of PCAR spectra of purely diffusive character by a ballistic model yield approximately the same (within

SUPPRESSION OF SUPERCONDUCTIVITY BY INJECTION OF SPIN-POLARIZED CURRENT

\ensuremath{\sim}3%

Bulk superconductivity above 100 K in the TlSrCaCu system

) values of the spin polarization and the barrier strength

Application of single electron tunneling: Precision capacitance ratio measurements

Z

Evidence for modification of the superconducting order parameter in YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// films by injection of a spin polarized current

larger by

One-step reaction and consolidation of Hg based high-temperature superconductors by hot isostatic pressing

\ensuremath{\sim}0.5--0.6