LaSr-manganate (LaSr)MnO3 with perovskite structure was prepared in the basic system MnO2–SrO–La2O3–B2O3(–SiO2) by a modified glass crystallization method. X-ray diffraction, magnetic measurements, EDX and particle size investigations (specific surface) were carried out. The influence of the annealing conditions on the phase composition and the magnetic properties of the powders are discussed. In the silicate-free system manganate powder samples show values of specific saturation magnetization up to 53 Am2/kg, a Curie temperature between 369 and 389 K and a mean particle size in the order of 100 nm. The powders reveal the magneto-resistive effect. In the silicate system the borate phase was leached out to get a manganate-SiO2 mixture which could be sintered to bulk samples. The sintering conditions have been varied to avoid a decrease of the magnetization due to the formation of non-magnetic phases. Sintered samples show a superposition of the CMR and the GMR effect due to grain boundaries.

(LaSr)MnO3 powders with perovskite structure were prepared in the basic system MnO2–SrO–La2O3–B2O3 for the first time by a modified glass crystallization method. The annealing temperature was changed between 600 and 950°C. X-ray diffraction, magnetic measurements, ESMA and particle size investigations (specific surface) were carried out. The influence of the annealing conditions on the phase composition, the cation contents and the magnetic properties of the powders is discussed. Powder samples prepared under optimized conditions show values of specific saturation magnetization between 48 and 53Am2/kg, a Curie temperature between 369 and 389K and specific surfaces of about 10m2/g corresponding to a mean particle size of 100nm. The powders reveal the magneto-resistive effect.

Doped La-manganites belong to the class of perovskite materials showing the so-called colossal magnetoresistance effect (CMR) near their Curie temperature Tc, which can be varied in a wide range up to 380K. The magnetoresistance (MR) ratio of sputtered epitaxial films changes strongly with their Tc from 8000% at 90K to 35% at 310K in a field of 1T. Bicrystalline and polycrystalline films show an additional MR effect below Tc. Whereas the CMR effect is caused by a magnetic phase transition the low-temperature MR effects are induced by the transport of spin-polarized carriers across grain boundaries acting as tunneling barriers. The CMR effect is interesting for applications especially in position sensors because of its large dynamic range without hysteresis and saturation effects.

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.

Tl/sub 2/Ba/sub 2/CaCu/sub 2/O/sub 8/ (TBCCO) thin films have been deposited on top of YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// (YBCO) thin films. Both layers are superconducting with T/sub c/ values of 105 K and 75 K respectively and in superconducting contact. XRD scans show the TBCCO film to grow epitaxially and c-axis oriented on the YBCO ground layer. Possible applications for such multilayers are novel concepts for intrinsic Josephson arrays requiring well defined mesa structures of TBCCO.

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.

For the visible spectral range different types of sensitive radiation detectors are available especially high sensitive and fast quantum detectors based on semiconducting materials. However, for the IR range there is a lack of detectors, especially for the FIR range between 10 µm and 1000 εm wavelength. This wavelength region is of actual importance for spectroscopic purposes as well as for communication systems. For spectroscopic investigations two competing techniques are under developement, the optical and the rf-technique.

TIBaCaCuO (TBCCO) belongs to a class of HTSC materials showing very high critical temperatures up to 127 K and a strong anisotropy of the superconducting properties. This is caused by a layered lattice structure responsible especially for the observed intrinsic Josephson effect. These properties are especially interesting for technological applications like passive microwave devices, microwave oscillators and mixers, voltage standards and switches. High quality epitaxial TBCCO films necessary for these applications are prepared by recrystallization of a TI free precursor film in a TIOx containing atmosphere at temperatures between 800 and 880 °C.

The intrinsic Josephson effect was sucessfully established with TIBaCaCuO thin films across a step in (100)LaAlO3 substrates (Step Stack junctions). I — V- characteristics showed all the single junctions in stack. Emitted microwave radiation was detected as broad, unsynchronized emission for temperatures close to Tc, but especially as sharp peaks resulting from phase locking at least of substacks for frequencies from 10 to 100 GHz. To improve the reproducibility and decrease parameter spread a in situ laser tuning was set up resulting in samples with Ic values up to 12 mA and a decrease in AIC of the individual junctions as well as of the McCumber parameter pc For further device applications a new concept and first experiments based on YBCO — TBCCO — multilayers are introduced

We have observed intrinsic Josephson effects for current flow perpendicular to the CuO2 planes in HTSC thin films. Tl-Ba-Ca-Cu-O thin films were deposited on step edges in LaAlO3 substrates. Due to the special preparation process, microbridges across such steps act as stacks of intrinsic Josephson junctions with current flow perpendicular to the CuO2 planes (STEP STACK junctions). Up to 130 individual junctions could be observed exhibiting high IcRN products up to 26 mV per junction. We observed ac-Josephson effects as Shapiro steps and in microwave emission experiments. At low temperatures sharp emission peaks were detected at frequencies of 11.3 and 24.2 GHz. Broad emission peaks from the whole stack were observed at temperatures close to Tc.

We have investigated the modification of high-Tc superconducting film structures due to ion beam irradiation using a mask technology. The YBa2Cu3O7 (YBCO) and GdBa2Cu3O7 (GBCO) thin film microbridges were covered with electron resits (PMMA) masks. Then, a submicron slit was patterned by e-beam lithography. The high-Tc bridges were modified by irradiation with argon ions. Fluence and energy of the ions could be varied and the change in the electrical properties of the modified regions have been measured. For suitable values of ion energy and fluence we measured Shapiro steps in the current-voltage curves under microwave irradiation for a temperature range of a few Kelvin just below the critical temperature. We found a modulation of the Shapiro steps with increasing microwave power and compared the power dependence to Josephson and flux flow behaviour. The Monte-Carlo program TRIM was used for characterization of the ion solid interaction, especially for the estimation of range, damage distribution and straggling in dependence on geometry.

Step Stack Junctions in TBCCO thin film act as series of intrinsic Josephson junctions. Synchronized microwave emission could be observed for at least substacks but as prepared still samples show a great spread in parameters. Here we report on additional in situ laser formation allowing to adjust junction parameters resulting in samples with high I-c values up to 12 mA and decreased Delta I-c and beta(c).

The deposition of high-T(c) superconducting thin films by magnetron sputtering of ceramic and alloy targets is strongly influenced by the bombardment of energetic oxygen particles generated and accelerated at the target surface. In this paper we examine different sputtering methods to overcome the disturbing effects of these energetic particles on the composition of the deposited films.

The goal of the project was the development of several variants of sputtering technology for producing highly textured HTSL layers on selected monocrystalline substrates with spectrum of properties suited for cryoelectronic elements, especially SQUID. (orig./MM) [Deutsch] Das Ziel des Forschungsprojektes bestand in der Erschliessung verschiedener Varianten der Sputtertechnik zur Herstellung hochtexturierter HTSL-Schichten auf ausgewaehlten einkristallinen Substraten mit einem Eigenschaftsspektrum, das zur Realisierung von kryoelektronischen Bauelement, insbesondere von SQUID`s geeignet ist. (orig./MM)