15 research outputs found
Superconducting properties of RuSr2GdCu2O8 studied by SQUID magnetometry
For polycrystalline RuSr2GdCu2O8 (Ru-1212), distinct peaks have been reported
in d.c. magnetization in the superconducting state of the sample. Sr2GdRuO6
(Sr-2116), the precursor for the preparation of Ru-1212, shows similar peaks in
the same temperature regime. Based on measurements performed on both bulk and
powdered samples of Ru-1212 and Sr-2116, we exclude the possibility, that the
observed behavior of the magnetization of Ru-1212 is due to Sr-2116 impurities.
The effect is related to the superconductivity of Ru-1212, but it is not an
intrinsic property of this compound. We provide evidence that the observation
of magnetization peaks in the superconducting state of Ru-1212 is due to flux
motion generated by the movement of the sample in an inhomogeneous field,
during the measurement in the SQUID magnetometer. We propose several tests,
that help to decide, whether the features observed in a SQUID magnetization
measurement of Ru-1212 represent a property of the compound or not.Comment: 22 pages, 9 figure
The Effect of Chemical Doping and Hydrostatic Pressure on Tc of Y1-yCayBa2Cu3Ox Single Crystals
We performed susceptibility measurements on Y1-yCayBa2Cu3Ox single crystals
under high He pressure. For each Ca content various samples with different
oxygen contents have been prepared to probe the influence of Ca on Tc(x),
dTc/dp(x) and Tc,max. Starting from the parabolic Tc(nh) behavior we calculated
nh values from Tc and Tc,max for each sample. It is shown that in the overdoped
region dTc/dp can be described by a pressure induced charge transfer with
dnh/dp = 3.7E-3 [1/GPa] and a dTc,max/dp value of 0.8 K/GPa, irrespective of
the Ca content. In the underdoped region additional pressure effects lead to a
peak in dTc/dp at approximately 0.11 holes/CuO2 plane. However, with increasing
Ca content this peak is strongly depressed. This is explained in terms of an
increasing disorder in the CuO chain system due to doping. Deviations in dTc/dp
at very low nh values can be assigned to the ortho II ordering in the CuO chain
system.Comment: 13 pages with 6 figures, accepted for publication in Physica