Publications

The results of magnetic measurements performed on ZrCo5.1-xFex alloys in the temperature range 4.2-900 K and fields up to 7 T are reported. The presence of solid solutions is evidenced in the composition range x < 0.9. The Curie temperature and the saturation magnetization increase nearly linearly when cobalt is substituted by iron. In addition, the anisotropy field decreases and shows an unusual temperature dependence, with a maximum at T congruent-to 300 K.

A Hendricks-Teller analysis of the X-ray diffraction line shifts in Bi-Sr-Ca-Cu-O phases allows an estimate of the stacking fault probabilities (missing or extra Cu-O layers). The probability values suggest some conclusions about the mutual relationships of the 2201, 2212 and 2223 phases and the kinetics of their formation.

The GdCo4-xNi(x)B alloys, for x less-than-or-equal-to 3 and GdCo4-xFe(x)B alloys for x less-than-or-equal-to 1.5 crystallize in a hexagonal structure of CeCo4B-type. The magnetic measurements performed in the temperature range 4.2-900 K show that GdCo4-xM(x)B compounds (M = Fe or Ni) are ferrimagnetically ordered. The mean cobalt moments increase when cobalt is substituted by iron and decrease when it is replaced by nickel. Above the Curie temperatures, the reciprocal susceptibilities for GdCo4-xNi(x)B alloys show a nonlinear temperature dependence. The exchange fields acting on cobalt atoms were evaluated. The variations of the cobalt moments are proportional to those of the exchange fields.

Using a simple Foldy-Lax model for the refractive index of photons in a nuclear medium and actual empirical gamma-N forward Compton scattering amplitudes we show that the "coherence condition" for the emission of gamma-Cerenkov radiation is fulfilled at incident energies higher than 16 GeV/nucleon in the gamma-spectral band 140 less-than-or-equal-to omega less-than-or-equal-to 160 MeV, still well below the DELTA resonance region. The predictions for gamma-cross sections are between 62-mu-b and 248-mu-b for projectile nuclei with 16 less-than-or-equal-to A less-than-or-equal-to 32. Also the complete linear polarization of the coherent gamma-Cerenkov radiation is pointed out.

The structure of vacuum annealed amorphous sputtered Cr and CrNi (55:45) thin films has been studied by transmission electron microscopy (TEM) and electron diffraction (TED). The thin films with thicknesses ranging from 150 to 600 angstrom were annealed while still on their alkali halide substrates under high vacuum at temperatures ranging from 200 to 370-degrees-C. The TEM and TED data permitted to establish the annealing conditions (temperature, duration), which lead to the nucleation and growth of nanosized crystals in the Cr and CrNi icosahedral glasses.

A magnetron with 75 cm2 effective area for reactive sputtering in pure oxygen was realised by modifying AV 500 standard equipment. Dielectric Al2O3 and Ta2O5 thin films of 30 cm2 area and thickness between 0.1-1-mu-m were obtained. Their amorphous structure and excellent visible transmission recommend them for electroluminescent devices production.1-3

Amorphous ribbons of (Fe1-xYx)84B16 with 0 < x < 0.21 were studied using Mossbauer and magnetic measurements. The results proved a short-range order interaction in the prepared samples and nonhomogeneous regions induced by yttrium presence.

The crystalline phases in the superconducting ceramic Bi:Sr:Ca:Cu2:O(x) exhibiting either low superconducting transition (almost-equal-to 80 K) or both, low and high superconducting transitions (almost-equal-to 110 K) are identified by X-ray and electron diffraction. Two types of modulated structures are observed and their relation to T(c) is discussed within the frame of the oxygen-displacive mode theory.