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: http://www.issp.ac.ru/lek/shovkun/abs14.html
Дата изменения: Sat May 22 20:22:32 2004 Дата индексирования: Tue Oct 2 03:12:23 2012 Кодировка: Поисковые слова: m 97 |
A scan of the superconductor-nonsuperconductor transformation in
single crystals of YBa2Cu3O6 + x
(x0.37) is done in two
alternative ways, namely, by applying a magnetic field and by
reducing the hole concentration through oxygen rearrangement. The
in-plane normal-state resistivity
ab
obtained in the two cases is quite similar; its temperature
dependence can be fitted by a logarithmic law in a temperature range
of almost two decades. However, an alternative representation of the
temperature dependence of
ab
= 1/
ab
by a power law, typical for a 3D material near a metal-insulator
transition, is also plausible. The vertical conductivity
c =
1/
c
followed a power law, and neither
c(T),
nor
c(T)
could be fitted by log T. It follows from the
c
measurements that the transformation at T = 0 is split into
two transitions: superconductor-normal-metal and normal-metal-insulator. In our
samples, they are separated in oxygen content by
x
0.025.
PACS: 72.15.Rn, 61.50.Ah, 74.62.Bf, 71.30.+h