6 research outputs found
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Observation of spin-dependent tunneling and large magnetoresistance in La{sub 0.7}Sr{sub 0.3}MnO{sub 3}/SrTiO{sub 3}/La{sub 0.7}Sr{sub 0.3}MnO{sub 3} ramp-edge junctions
The authors have fabricated ferromagnet-insulator-ferromagnet tunneling junctions using a ramp-edge geometry based on (La{sub 0.7}Sr{sub 0.3})MnO{sub 3} ferromagnetic electrodes and a SrTiO{sub 3} insulator. Pulsed laser deposition was used to deposit the multilayer thin films and the devices were patterned using photolithography and ion milling. As expected from the spin-dependent tunneling, the junction magnetoresistance is dependent on the relative orientation of the magnetization in the electrodes. A junction magnetoresistance (JMR) as large as 30% is observed at low temperatures and low fields. In additino, they have found that JMR is reduced at high temperatures (T > 100 K) and decreases monotonically with increasing field at high fields (0.5 T < H < 1 T). Possible causes for these are also discussed
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Electrodynamic Properties of Single-Crystal and Thin-Film Strontium Titanate
The authors present a comparative study of broadband electrodynamic properties of coplanar waveguides made from nonlinear dielectric single-crystal and thin-film SrTiO{sub 3} (STO) with high-temperature superconducting thin-film YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} electrodes. The waveguides that use single-crystal STO exhibit a monotonic increase in refractive index, dielectric nonlinearity, and dissipation with decreasing temperature (from 80 K to 20 K), whereas those based on thin-film STO show similar but weaker effects with increasing temperature. Under dc bias, both types of waveguides show reduced refractive index, but dissipation increases in the case of single-crystal STO, while it decreases in the case of STO thin-films
Tunable microwave mixing in nonlinear dielectric thin films of SrTiO3 and Sr0.5Ba0.5TiO3
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Microstructure and properties of in-situ rf sputtered YBa sub 2 Cu sub 3 O sub 7 thin films for microwave applications
The residual surface resistance of a number of films of YBa{sub 2}Cu{sub 3}O{sub 7}, prepared by off-axis sputtering onto MgO substrates, has been measured using parallel-plate resonator technique. Deposition conditions were kept constant, apart from the substrate temperature. There is no correlation between surface resistance and other important microscopic parameters, such as T{sub c} and c-axis lattice parameter. There is, however, a trend to higher R{sub s} with increasing volume fraction of in-plane misoriented material, although the correlation is not perfect. Furthermore, we have found that most of the misoriented material is localized at the film substrate interface and therefore is probably not responsible for most of the RF losses. The data suggest that at higher deposition temperatures, there is an increasing tendency for 45{degrees}-misoriented material to appear in the films, and it may be that a significant fraction of this material is present closer to the free film surface. STM qualitatively supports this conclusion