  When investigating low-frequency (0.1 Hz) oscillations of miltiphase
high-temperature cuprate superconductors (HTSC) Bi1,7Pb0,3Sr2Ca(n-1)CunOy
(n=2-30), a wide attenuation peak with a maximal at T=200K detected. This peak
was particularly pronounced in field cooling (FC) experiments, i.e. after
abrupt cooling of the sample in the external magnetic field at the temperature
T less Tc with subsequent slow warming up to room temperature with invariance
of applied field. The attenuation peak height depended on the preliminary
orientation (before cooling) of the samples in the measured permanent magnetic
field H. On the one hand, it is well khow that, after the FC procedure and
subsequent slow warming up, at the temperatures close to the critical
temperature Tc, the attenuation peak associated with "melting" of the Abrikosov
frozen vortex structure and its disappearance at T more Tc is detected in
monophase samples. At the same time, in most multiphase bismuth HTSC samples,
synthesized using solar energy and superfast quenching of the melt, the
attenuation peak with the maximum at T=200K was observed. Depending on the
conditions of synthesis, the attenuation peak could be two-humped and could be
located in the temperature range much wider than Tc of the major
superconducting phase. We assume that this is due to the existence of frozen
magnetic fluxes (after FC) in superconducting "dropping" regions, which
gradually (with increasing temperature) transfer into the normal state and
release pinned vortex threads. This fact could be a sause of observed
dissipative processes, so as also the evidence of the existence of
superconductivity at T more 240K.
