Superconducting properties of RuSr2GdCu2O8 studied by SQUID magnetometry

For polycrystalline RuSr2GdCu2O8 (Ru-1212), distinct peaks have been reported in d.c. magnetization in the superconducting state of the sample. Sr2GdRuO6 (Sr-2116), the precursor for the preparation of Ru-1212, shows similar peaks in the same temperature regime. Based on measurements performed on both bulk and powdered samples of Ru-1212 and Sr-2116, we exclude the possibility, that the observed behavior of the magnetization of Ru-1212 is due to Sr-2116 impurities. The effect is related to the superconductivity of Ru-1212, but it is not an intrinsic property of this compound. We provide evidence that the observation of magnetization peaks in the superconducting state of Ru-1212 is due to flux motion generated by the movement of the sample in an inhomogeneous field, during the measurement in the SQUID magnetometer. We propose several tests, that help to decide, whether the features observed in a SQUID magnetization measurement of Ru-1212 represent a property of the compound or not.Comment: 22 pages, 9 figure

Target Dependence of Slow Electrons Emitted in Swift Ion-Atom Collisions

Low-energy electron emission is studied for 3.6-MeV/u Au53+ impact on Ne and Ar using the first-Born and continuum-distorted-wave eikonal-initial-state (CDW-EIS) approximations. By using optimized effective potentials to represent the target atom, very good agreement is obtained between the CDW-EIS results and experiments. The comparison with the calculations using the first-Born approximation shows that the emission is very asymmetric, with a preferential emission into the forward direction. A detailed study of the emission from each initial orbital of the target atom reveals features in the spectra which can be related to the structure of the initial-state bound wave function

Computation of Distorted Wave Cross Sections for High-Energy Inelastic Collisions of Heavy Ions with Water Molecules

Irradiation of water and other molecules of biological interest by heavy ion beams is studied. Distorted wave models are employed to investigate the corresponding inelastic collisions. Cross sections for electronic capture, ionization, and excitation processes are determined as well as equilibrium charge-states and electronic stopping power. The influence of multiple ionization in liquid water radiolysis is analyzed

Imaging optical near fields at metallic nanoscale voids

Direct imaging of the electromagnetic fields generated by plasmon excitation at gold nanoscale voids is achieved with high spatial resolution using scanning near-field optical microscopy (SNOM). The spatial intensity distribution of the electromagnetic field in spherical Au void structures strongly depends on the light excitation wavelength and on the diameter and degree of truncation of the voids. Comparing the SNOM results with reflectivity measurements and boundary element calculations allows for a clear identification of the plasmon modes being activated in each case. The unique mapping of the high-field regions provides key information for the use of void nanostructures as substrates for surface-enhanced Raman scattering