A.G. Maresov

Properties of the YBCO thin film interferometers fabricated on ZrO/sub 2/ bicrystal substrates

The properties of DC SQUIDs made of YBCO thin film deposited on ZrO/sub 2/ bicrystal substrate and the nature of the fabricated Josephson junctions have been studied. It is found that the characteristics of the junctions are similar to those of the SNS structures with paramagnetic impurities in the N layer. A level of interferometer noise close to 5*10/sup -4/ Phi /sub 0//Hz/sup 1/2/ and a magnetic field sensitivity of 10/sup -10/ T/Hz/sup 1/2/ at frequencies higher than 25 Hz in the usual feedback mode of the SQUID operation have been achieved at 77 K.

Study of amorphous ferromagnetic microwires using a scanning SQUID microscope

Abstract The magnetic properties of amorphous ferromagnetic 30–50-μm diameter microwires produced by means of spinning process are studied both experimentally and theoretically. The magnetic images of the microwire are measured at 77 K with the high-spatial resolution scanning SQUID microscope in an axial magnetic field up to 103 A/m. The values of the local magnetic fields produced by the microwire in remnant state are typically a few μT at a distance 50–100 μm far from the sample. It is shown that the wires domain structure calculated numerically is in a qualitative agreement with the magnetic images obtained experimentally.

YBCO THIN-FILMS SQUIDS FABRICATED ON BICRYSTAL SUBSTRATES

Properties of the dc SQUIDs made of YBCO thin film deposited on SrTiO3 and ZrO2 bicrystal substrates and the properties of the fabricated Josephson junctions have been studied. It is found that the characteristics of the junctions are similar to those of the SNS structures. The magnetic field sensitivity has achieved a value of δB ~ 10−12 T/Hz1/2 at frequencies higher than 25 Hz and T = 4.2 K.

The physical basis of the fabrication of the third generation of high-temperature superconducting wires on quartz substrates

The problem of the fabrication of third-generation high-temperature superconductors (HTSCs) that are designed for the transmission of electric energy and the creation of nanoelectronic devices is studied in this work. The issues of the fabrication of dielectric substrates for the third generation wires are considered. The technology of HTSC film deposition on the quartz substrates is presented. Complex studies of sputtering of the buffer and superconducting YBa2Cu3O7 − δ (YBCO) layers were performed. The results of studies of electrophysical properties of the HTSC films on the quartz substrates are discussed.

SQUID-Based Relaxometric Diagnostics of Magnetic Nanoparticles

The method of SQUID-based relaxometric diagnostics has been applied to the ensembles of non-interacting near-spherical Fe3O4 and Co nanoparticles in order to reveal the behavior of the anisotropy constant upon varying the molecular surrounding of nanoparticles by using different polymer matrices. The transmission electron microscopy (TEM) and X-ray diffraction techniques have been employed to obtain the structural information about objects of study. The relaxation curves measured with the SQUID-relaxometer in the time range from about 50 s to several tens of seconds after application of a pulse of low dc magnetizing field have been approximated by theoretical dependences calculated within the framework of activation Néel–Arrhenius law with account for the size distribution functions retrieved from TEM data. From results of approximations, the values of anisotropy constant have been determined.

A new software for the processing of SQUID-microscopy images

We have developed a program running on the Windows platform which enhances the quality of two-dimensional images acquired by a scanning SQUID microscope. The program can also be used for image processing of data from other SQUID based systems, such as eddy current SQUID NDE systems. A general description of the program and the incorporated additional digital filters for removing image artifacts in the Fourier space is given. The user interface is presented as well as several examples of this software applications to real images.

Optical diagnostics for fabrication of YBCO thin film DC SQUIDs

Optical reflectance spectra of thin YBCO films on SrTiO/sub 3/ bicrystals were measured in a photon energy range of 1-3 eV at room temperature. Raman spectra measurements in the range 200-700 cm/sup -1/ were performed. The best samples were shown to have high reflectance anisotropy and a well-defined Raman peak /spl nu//sub 1/=500+1 cm/sup -1/. YBCO thin films on a bicrystal substrate that successfully passed optical control were used for Josephson junctions and DC SQUID fabrication. The fabricated SQUIDs operated at 77.3 K in the flux locked loop mode and had a typical white noise (1-2)/spl times/10/sup -5/ /spl Phi//sub 0//Hz/sup 1/2/ at frequencies higher than 200-500 Hz. The best magnetic field resolution was 650 fT/Hz/sup 1/2/ at frequencies f>200 Hz.<<ETX>>

Detection properties of thin film high-Tc bridges on bicrystal substrate

Abstract We report on the detection properties of the Josephson grain-boundary junctions fabricated from an epitaxial YBa 2 Cu 3 O 7−x thin film on a bicrystal SrTiO 3 substrate at 37–70 GHz and 77 K.

Detection of YBCO Film Monocrystalline Domains by Optical Measurements

We used a method based on thepolarized light reflectivity measurements to Investigate YBa2Cu307−x films deposited by laser on SrTiO3 (100). From reflectivity measurements the domains with the largest optical anisotropy have been detected. Specific dimensions of them were ∿1 mm. Within one of these domains the SQUID interferometer was fabricated. The configuration of the interferometer (the dimension of the loop was 30×30 μm) was obtained by direct laser writing. The measurement was seems considerable concentration of the magnetic field into the SQUID loop. The effective quantum flux corresponded to the loop with linear size equal to few hundred microns.