Oxide heterostructures were used for studies of quasiparticle injection effects in high-Tc superconducting thin films. The effect of injection of spin polarized quasiparticles from a ferromagnetic gate layer was compared to that of unpolarized quasiparticles from a nonmagnetic metallic gate. Transport measurements of the superconducting layer showed strong suppression in the supercurrent by the injection of spin-polarized quasiparticles, and a current gain of as large as five was attained. This is 10 to 30 times larger than the gain of unpolarized injection devices. Such large effects could be useful in a variety of active high-Tc superconductor/colossal magnetoresistance heterostructure based devices.

Since the rejuvenation of interest in the rare earth manganites owing to their potential use as magnetoresistive sensors, there has been adequate research to arrive at some evaluation of the potential for these materials in a variety of technologies that would use the peculiar properties of these materials. The magnetic field sensitivity of the transport properties, the strong metal insulator transition at the Curie temperature, the electric field polarizability of the material and its subsequent effect on the transport properties, the half metallicity of the electronic bands, etc., are properties of the rare earth manganites that could be exploited in a variety of devices. In this review we explore the various interesting technological avenues that are being pursued and address the uniqueness of the material that may enable a given technology as well as the various bottlenecks that will have to be overcome in order to successfully compete with the existing technologies. As is the case with many emerging materials technologies, the devices also serve as a vehicle for further understanding of the fundamental mechanisms behind the basic properties of the materials.

A very large positive magnetoresistance (MR) has been discovered in a Fe3O4/SrTiO3/ La0.7Sr0.3MnO3 heterostructure for the transport perpendicular to the layer planes and applied magnetic field in the film plane. The observed MR features do not show any obvious correlation with the hysteresis behavior of the ferromagnetic bilayers. A possible explanation of these results is given in terms of the relative differences in the majority and minority spin bands of the two ferromagnetic layers and the field induced modifications of domain structures therein.

A bstract-A three terminal device was fabricated by depositing a thin film of Ca-doped SmBa2Cu30y on a bicrystal SrTi03 substrate and then structuring a gate over the resulting junction.The channel shows RSJ-like Josephson junction behavior. By applying a voltage to the gate, a large electric field effect was observed. The largest field effect was observed in films where 30% of the Sm was replaced by Ca. The critical current of the junction was modulated 23% by the application of an electric field of 5~1 0~ V/cm. This electric field is about 100 times smaller than the electric field necessary for the field effects observed in homogeneous films. The sign of the field effect is consistent with that expected for a carrier-depleted grain boundaky region.

We have fabricated vertical YBa 2Cu3O7−x/PrBa 2Cu3O7−x/YBa 2Cu3O7−x (YBCO/PBCO/YBCO) Josephson junctions using in-plane aligned a-axis oriented YBCO multilayers on (100) LaSrGaO4(LSGO). The Tc’s of the device electrodes are typically greater than 80 K. Josephson coupling is observed for barrier thickness up to 800 Å. Strong nonlinear I–V characteristics arising from the properties of PBCO are observed for thicker barrier devices. Chip to chip spread in the device characteristics may be intrinsically due to the PBCO barrier.