A superconducting point contact is used to determine the spin polarization at Fermi energy of several metals. Because process supercurrent conversion a superconductor-metal interface (Andreev reflection) limited by minority population near surface, differential conductance can reveal metal. This technique has been applied variety metals where ranges from 35 90 percent: Ni0.8Fe0.2, Ni, Co, Fe, NiMnSb, La0.7Sr0.3MnO3, and CrO2.

Using the point-contact Andreev reflection technique, we have carried out a systematic study of spin polarization in colossal magnetoresistive manganite, ${\mathrm{La}}_{0.7}{\mathrm{Sr}}_{0.3}{\mathrm{MnO}}_{3}$ (LSMO). Surprisingly, observed significant increase current with residual resistivity. This counterintuitive trend can be understood as transition from ballistic to diffusive transport contact. Our results strongly suggest that LSMO does minority states at Fermi level. However,...

It is demonstrated here that granular films of Y-Ba-Cu-O may serve as optical detectors, operating at wavelengths from the visible to far infrared, temperatures well above liquid helium. Preliminary measurements using a blackbody source show an upper bound minimum detectable power 1 μW. The response time determined by pulsed far-infrared order 20 ns. Methods improve sensitivity will be discussed.

We have developed a simple method to measure the transport spin polarization of ferromagnetic materials. This technique relies on fact that Andreev reflection process at interface between superconductive and normal is influenced by P metal. In very short time we been able several metals: NixFe1−x, Ni, Co, Fe, NiMnSb, La0.7Sr0.3MnO3, CrO2, whose ranges from 35% 90%. Our results compare well with other methods for measuring P.

Highly spin-polarized chromium dioxide (CrO2) thin films were deposited on (100) TiO2 substrates by chemical vapor deposition using chromyl chloride as a precursor. The spin polarization, measured the point contact Andreev reflection technique, was 81±3%. X-ray diffraction θ/2θ scans indicated grew completely oriented, in registry with oriented substrate. φ CrO2 (110) expected twofold symmetry, no evidence of misaligned material. resistivity at room temperature 240 μΩ cm and decreased to 10...

Nb-Ta multilayered films prepared by magnetron sputtering have been studied critical-field measurements. We examined the effects of substrate orientation and deposition temperature on properties films. Three-dimensional to two-dimensional crossover is observed. For with larger Nb layer thicknesses an additional transition in ${H}_{c2?}$ at lower temperatures observed which cannot be accounted for interfacial regions.

Critical-current measurements have been made on sputtered Nb-Ta multilayers for both perpendicular and parallel applied field. For large bilayer periods, the pinning force behaves as h(1-h) is due to dislocation pinning. As period decreases, decreases changes over a collective mechanism. field, there lack of temperature scaling an increase in force, which by multilayering. A search existence other effects discussed.

We have prepared thin films of Y1Ba2Cu3O7−x using a coevaporation technique and measured their critical current densities as function both temperature field transport technique. For stoichiometric composition we find that Jc at 4.2 K in zero is 1.04×106 A/cm2 does not drop below 105 until T>60 K. Fitting the data near Tc shows follows power law (1−t), with t being reduced temperature. In an applied perpendicular to film’s surface, also drops slowly, up 90 kOe Jc>105 for T=4.2...

The application of a DC magnetic field to disordered or granular films Y-Ba-Cu-O is shown lead an enhancement nonbolometric photoresponse at temperatures near and below T/sub c/. disorder evidenced by the broadened resistive transition superconductivity higher normal state resistance films. This observation consistent with nonequilibrium effect, which described flux-flow model low-temperature superconductors.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML"...

The structure and superconducting properties of sputtered Nb-Ta multilayers are studied as a function the bilayer period \ensuremath{\Lambda}. films mosaic structures with single-crystal diffraction profiles. elastic mean free paths in both niobium tantalum layers larger than layer thicknesses. measured transition temperatures perpendicular critical field slopes compared to predictions proximity theory. parallel fields angular dependences examined for occurrence three-dimensional...

The superconducting critical temperature, ${\mathit{T}}_{\mathit{c}}$, of different configurations layers is studied under the de Gennes--Werthamer model. Certain inconsistencies are seen to develop with use this approach, calling into question previous results obtained. Preliminary on Nb/Zr layered structures also presented.

We present the first specific-heat measurements of artificially layered superconducting structures. Using small sample calorimetry, we have measured specific heat Nb-Zr multilayers. Samples with $\ensuremath{\Lambda}$, bilayer period, varying from 32.8 to 429 \AA{} (with total thickness 1.5 \ensuremath{\mu}m) were studied in a temperature range 1.5-20 K. obtained effective ${\ensuremath{\theta}}_{D}$ and $\ensuremath{\gamma}$ for samples as well...

A new method for determining the transport spin polarization, point contact tunneling from a low temperature superconductor into ferromagnet, is used to determine polarization of several LaSrMnO thin films and crystals. The Andreev process its utility in measurements spin-polarization are described. Preliminary results LSMO presented.

The superconducting and magnetic properties of thin films ferromagnetic iron Permalloy deposited on ${\mathrm{YBa}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{7\mathrm{\ensuremath{-}}\mathrm{\ensuremath{\delta}}}$ have been investigated. were 50--300 A\r{} thick, while the 1000--2000 thick. not affected by presence layers, but marked changes in resonance spectra observed, including appearance a large temperature-dependent anisotropy. These effects are attributed to development spin-glass-like...

The occurrence of a transverse voltage peak has been observed in YBCO thin films. This phenomenon occurs under conditions temperature and current the earth's magnetic field such that films are mixed state. magnitude was found to scale with both current, exhibited Sin(/spl theta/) orientational dependence measured between film-substrate position measurement electrodes on film surface. These observations similar made conventional superconducting as Nb, NbN, NbCN, PbBi.< <ETX...

We have grown thin films of (100) oriented La_{0.67}(Ca_{x}Sr_{1-x})_{0.33}MnO_{3} on NdGaO_{3} substrates by off-axis sputtering. looked at the changes in resistivity and magnetoresistance samples as Ca/Sr ratio was varied. find that calcium fraction is decreased, lattice match to substrate decreases, become more disordered, observed transport measurements variation Curie peak resistance temperatures. a correlation between temperature independent T^2 terms low resistivity. The room exhibits...

Novel electronic properties are observed in metals contact with the ferromagnetic insulator europium monoxide (EuO). We have successfully prepared epitaxial bilayers and multilayers involving EuO V or Ag. With metal layers of 100 angstroms thickness less, these structures exhibit a slope discontinuity their resistance versus temperature at 90 K for V/EuO interfaces 50 Ag/EuO interfaces. For less than about 40 angstroms, feature is also apparent R(T) 70 K, Curie bulk EuO. The discontinuities...

The magnetoquenched superconducting valve is a nonvolatile switch consisting of ferromagnetic film that spans strip. A device state dictated by the magnetization orientation element and corresponding magnetic fringe fields at its edge which control critical current in underlying superconductor. Pb-based has been fabricated with “write wire” inductively coupled to layer as an integrated line. pulse through line produces small local field larger than coercivity Hc ferromagnet orients...

We have prepared thin film composites of Y1Ba2Cu3O7−y (‘‘123’’) and Y2Ba1Cu1O5 (‘‘211’’) by off-axis sputtering from separate targets the 123 211 material. X-ray diffraction on films shows presence c-axis oriented 123, (00L) ordered Y2O3, but no indication lines. The lattice constant does not show any change compared to our pure films. As volume percentage material increases, we see a reduction in Tc Jc, an increase resistivity. temperature field dependence critical current are different for

Three variations of sputtering for growing thin films Y/sub 1/Ba/sub 2/Cu/sub 3/O/sub 7-x/ are examined: a three-metal cosputtering technique requiring postanneal at high temperatures, an in situ process using inverted cylindrical magnetron sputter gun, and another planar target off-axis geometry. The grown primarily on magnesium oxide substrate because it is readily available, inexpensive, its low dielectric constant permits convenient microwave circuit design. It found that the cosputter...