Bi. Belevtsev et al., SUPERCONDUCTIVITY EFFECTS IN HOPPING CONDUCTIVITY OF LA2CUO4 SINGLE-CRYSTAL WITH EXCESS OXYGEN, Low temperature physics, 23(4), 1997, pp. 274-280
hopping conductivity of La2CuO4+delta single crystal with excess oxyge
n has been studied. It is found that the transition from variable-rang
e hopping (with the temperature dependence of resistance R proportiona
l to exp(T-0/T)(1/4)) to simple activation conductivity (R proportiona
l to exp(Delta/kT)) occurs at a temperature lower than 20 K. This tran
sition is accompanied with significant changes in the behavior of magn
etoresistance and current-voltage characteristics. It is shown that su
ch a behavior of hopping conductivity below 20 K is due to the presenc
e of superconducting inclusions in insulating sample due to phase sepa
ration of La2CuO4+delta. The observed peculiarities in the conducting
properties are in good agreement with the known effects of competition
between electron localization and superconductivity in homogeneous sy
stems. (C) 1997 American Institute of Physics.