Epitaxial ferromagnetic manganite films have been sputtered on bicrystal substrates. Their magnetoresistance was measured as a function of magnetic field and temperature. The grain boundary magnetoresistance at low temperature is separated from the intrinsic magnetoresistance near the Curie temperature. The grain boundary magnetoresistance peaks at about 100 Oe and saturates at about 2 kOe. For a La0.8Sr0.2MnO3 film with a grain boundary angle θ=36.8° a field independent component r0=4.1×10−6 Ω cm2 was separated from a field-dependent component which has its maximum rH=2.3×10−6 Ω cm2 for H of order the coercive field.

The paper presents a detailed discussion of the current-voltage characteristic of intrinsic Josephson junctions in Bi 2 Sr 2 CaCu 2 O 8ϩ␦ and Tl 2 Ba 2 Ca 2 Cu 3 O 10ϩ␦ . In these materials Josephson tunnel junctions are formed naturally between adjacent superconducting CuO 2 bilayers or trilayers. A typical sample consists of a stack of Josephson junctions. We explicitly show that all junctions inside a given sample have identical tunneling characteristics. We discuss the shape ͑general curvature͒ of the current-voltage characteristic in terms of a superconducting order parameter that has a predominant d x 2 Ϫy 2 symmetry. The I c R n product of the intrinsic Josephson junctions turns out to be 2-3 mV, about 10% of the maximum energy gap ⌬ 0 /e. The currentvoltage characteristic of every individual junction exhibits pronounced structures in the subgap regime. They are best explained by a recently proposed resonant coupling mechanism between infrared active optical c-axis phonons and oscillating Josephson currents.

Epitaxial ferromagnetic La0.8Sr0.2MnO3−δ films have been sputtered on SrTiO3 bicrystal substrates. Etched patterns crossing the bicrystal grain boundary are compared with identical patterns not crossing it. The films were annealed at different conditions and their magnetoresistance measured as a function of temperature T and of in plane magnetic field H strength and direction. Annealing at 900 °C was found to modify the grain boundary and to increase its magnetoresistance. For H=±80 Oe parallel to the grain boundary and T=32 K narrow magnetoresistance peaks of 60% height are measured. They are interpreted in the frame of an in plane magnetotunneling structure.

Stable platinum oxide films have been prepared through magnetron sputtering and have been analyzed on the bases of energy-sensitive microanalyses, x-ray diffraction, resistivity, and optical reflectance measurements. The complex dielectric function has been determined for various oxygen contents in the film covering the wave-number regime 50 cm−1–λ−1–50 000 cm−1. The vibrational properties are dominated through a strong band, centered at 765 cm−1, associated with a asymmetric stretching mode of the Pt—O bond. The films are amorphous, with chemical composition PtOx, where 1<x<2.1, and are considered as a homogeneous solid solution of PtO and PtO2. The materials system displays a conductor–insulator transition at x≥2, in connection with an optical band gap Eg of ∼1.2 eV in the fully oxidized state. The conduction mechanism over the whole range of compositions is thermally activated and is determined through a large density of localized states extending into the band gap. At x<2 the optical gap disappears, consistent with the semimetallic behavior of the materials system for this range of composition.

High-T c GdBa 2 Cu 3 O 7Ϫ␦ superconductor bolometers with operation temperatures near 89 K, large receiving areas of 0.95 mm 2 and very high detectivity have been made. The bolometers are supported by 0.62 m thick silicon nitride membranes. A specially developed silicon-on-nitride layer was used to enable the epitaxial growth of the high-T c superconductor. Using a gold black absorption layer an absorption efficiency for wavelengths between 70 and 200 m of about 83% has been established. The noise of the best devices is fully dominated by the intrinsic phonon noise of the thermal conductance G, and not by the 1/f noise of the superconducting film. The temperature dependence of the noise and the resulting optimum bias temperature have been investigated. In the analysis the often neglected effect of electrothermal feedback has been taken into account. The minimum electrical noise equivalent power ͑NEP͒ of a bolometer with a time constant of 95 ms is 2.9 pW/Hz 1/2 which corresponds with an electrical detectivity D* of 3.4ϫ10 10 cm Hz 1/2 /W. Similar bolometers with ϭ27 ms and NEPϭ3.8 pW/Hz 1/2 were also made. No degradation of the bolometers could be observed after vibration tests, thermal cycling and half a year storage. Measurements of the noise of a Pr doped YBa 2 Cu 3 O 7Ϫ␦ film with T c ϭ40 K show that with such films the performance of air bridge type high-T c bolometers could be improved.