Aj. Zaleski et J. Klamut, Anisotropy of the penetration depth in La2-xSrxCuO4 in underdoped and overdoped regions, J PHYS-COND, 11(48), 1999, pp. 9731-9740
We present the results of measurements of the penetration depth anisotropy
in pulverized, ceramic La2-xSrxCuO4. The measurements were carried out for
x = 0.08, 0.1, 0.125, 0.15 and 0.2. The powdered samples, immersed in wax,
were magnetically oriented in a static magnetic field of 10 T The penetrati
on depth in the a-b plane, lambda(ab), and perpendicular to it, lambda(perp
endicular to), were derived from alternating-current susceptibility measure
ments. For underdoped samples they both vary linearly with temperature (for
the low-temperature region), while for the samples from the overdoped regi
on the measured points can be fitted by an exponential function. These resu
lts support Uemura's picture (Uemura Y J 1997 Physica C 282-287 194) of cro
ssover from Bose-Einstein condensation to a Bardeen-Cooper-Schrieffer mecha
nism of superconductivity. The penetration depth values extrapolated to T =
0 may be described by a quadratic function of the strontium concentration
(for both lambda(ab) and lambda(perpendicular to)). The anisotropy of the p
enetration depth as a function of the substitution shows a similar dependen
ce to the critical temperature T-c(x).