S. Sarti

A cavity system for the measurement of the surface resistance at 48 GHz in high- superconductors

We describe a system for the measurement of the surface resistance of high- superconductors (HTCSs) at 48 GHz as a function of the temperature, the external magnetic field and its orientation with respect to the crystallographic axes of the sample. The set-up is based upon a resonant cavity. Thin films, bulk ceramics and single crystals can be accommodated in the cavity. A geometry in which there is no c axis microwave current flow, or c axis microwave field penetration, is chosen, so that unwanted effects depending on the anisotropy of HTCSs are ruled out. Geometrical factors for samples smaller than the cavity endplate are calculated. Some measurements on HTCS thin films and single crystals are presented, as well as some of the items of physical information obtainable from the measurements.

New aspects of microwave properties of Nb in the mixed state

We present a study of the frequency dependence of the vortex dynamics in a conventional superconductor. We have employed a swept frequency, Corbino disk technique to investigate the temperature (3.6 K -T c ) and high-field (from H c2 /2 to H c2 ) microwave complex resistivity in Nb thin (20-40 nm) films as a function of the frequency (1-20 GHz). We have found several previously unnoticed features: (i) a field-dependent depinning frequency in the GHz range; (ii) deviations from the accepted frequency dependence [1], than can be ascribed to some kind of vortex creep; and (iii) the presence of switching phenomena, reminiscent of vortex instabilities. We discuss the possible origin of the features here reported.

Excess conductivity of overdoped Bi 2 Sr 2 CaCu 2 O 8 + x crystals well above T c

We have used a multiterminal technique in order to measure the

Determination of the resistivity components ρab and ρc from multiterminal measurements in Bi2Sr2CaCu2O8+x crystals

(\mathit{a},\mathit{b})

TWO TECHNIQUES FOR BROADBAND MEASUREMENT OF THE SURFACE IMPEDANCE OF HIGH CRITICAL TEMPERATURE SUPERCONDUCTING THIN FILMS

plane excess conductivity

ANISOTROPIC RENORMALIZED FLUCTUATIONS IN THE MICROWAVE RESISTIVITY IN YBA2CU3O7-DELTA

\ensuremath{\Delta}\ensuremath{\sigma}

Magnetic 3D-2D crossover in Bi2Sr2CaCu2O8+x

in several

High Frequency Resistivity in YBa2Cu3O7-δ: Effects of Anisotropic Renormalized Fluctuations

{\mathrm{Bi}}_{2}{\mathrm{Sr}}_{2}{\mathrm{CaCu}}_{2}{\mathrm{O}}_{8+x}

Vortex motion in Nb/PdNi/Nb trilayers: New aspects in the flux flow state

single crystals. We find that the experimental

Effects of dimensional crossover on the resistivity in Bi2Sr2CaCu2O8+x crystal

\ensuremath{\Delta}\ensuremath{\sigma}