E. Silva et al., ANISOTROPIC PROPERTIES OF THE MICROWAVE MAGNETO-DISSIPATION IN HIGH-T-C SUPERCONDUCTING FILMS, Applied magnetic resonance, 8(1), 1995, pp. 11-23
Citations number
34
Categorie Soggetti
Spectroscopy,"Physics, Atomic, Molecular & Chemical
we report measurements of the magnetic field dependent microwave dissi
pation at 21 GHz in Bi2Sr2CaCu2O8+x epitaxial films and in oriented YB
a2Cu3O7-delta films, by means of the end-wall-replacement cavity techn
ique. The power reflected by the tuned cavity is measured as a functio
n of the external magnetic field H and of the angle theta between H an
d the (a, b) planes, at fixed temperatures. In Bi2Sr2CaCu2O8+x, apart
from a narrow (Delta theta approximate to 0.5 degrees) angular range c
lose to the parallel orientation, the strongly anisotropic dissipation
exhibits striking scaling properties: all the data at fixed temperatu
re can be made to collapse on a single curve with a simple angular sca
ling of the magnetic field: H --> H/f(theta). It is found that the ani
sotropy ratio f(0 degrees)/f(90 degrees) increases with temperature. I
t is shown that the scaling function f(theta) and its temperature evol
ution are in agreement with the model for a quasi-2D superconductor. I
n YBa2Cu3O7-delta the presence of the flux-flow dissipation prevents t
he application of a scaling procedure, and a specific model must be ap
plied. We obtain that the anisotropy is almost constant with the tempe
rature, as predicted for a three-dimensional, anisotropic superconduct
or.