Thermoelectric power studies of a Nd1.82−xSrxCe0.18CuOy
superconducting system (abstract)
Okram G. Singh, B. D. Padalia, Om Prakash, V. N. Moorthy, and Anant V. Narlikar
Citation: J. Appl. Phys. 75, 6740 (1994); doi: 10.1063/1.356855
View online: http://dx.doi.org/10.1063/1.356855
View Table of Contents: http://jap.aip.org/resource/1/JAPIAU/v75/i10
Published by the American Institute of Physics.
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Thermoelectric power studies of a Nd, ~82~xSrxCe0~18Cu0,,superconducting
system (abstract)
Okram G. Singh and B. D. Padalia
Physics Department, Indian Institute of Technology, Bombay 400 076, India
Om Prakash
Materials Science Centre, Indian Institute of Technology, Bombay 400 076, India
V. N. Moorthy and Anant V. Narlikar
National Physical Laboratory, New Delhi 110012, India
We have reported recently on the revival of superconductivity in Ndl&eO~rsCuOy by doping with
a divalent alkaline earth element. The doped superconductor Nd,,s~_,Sr,Ceo.lsCuOy has a NdzCuO,
(T’- type) structure. This system possesses a normal state metallic resistivity [p(T)]
in
polycrystalline form. The p(T) versus temperature (T) plots are, in general, linear. We report here
the results of our studies of p(T) and thermopower S(T) and their dependence on the lattice oxygen
content (y) that is a function of the Sr-content X. The dp( T)/dT improves and then deteriorates with
an increase in y. However, the thermopower behavior is a more complicated function of y (or x) and
its results indicate that the majority of the charge carriers are electronlike. The thermopower (in
absolute value) of the superconducting Nd,,73Sro,osCeo,lsCuO~.~~compound gradually decreases
from 250 to 150 K, remains almost constant from 150 to 75 K, decreases very fast below 75 K, and
shows negative dS/dT. The overall feature of the S vs T plot suggests that the main contribution to
and other electron-doped superconductors,
S is from diffusion. Unlike reduced Nd1,82Ce0,1sCu04~01
we have not observed a peak near the transition temperature (T,) on the higher temperature side of
the S vs T plot of the present sample. An attempt is made to explain the salient features of the
thermopower.
The magnetic and superconducting
R=Pr, Ce, and Cm (abstract)
properties
of PbpSr,(R/Ca)Cu308,
J. Simon Xue, C. W. Williams, and L. Soderholm
Argonne National Laboratory, Argonne, Illinois 60439
The series of compounds Pb2Sr,(R/Ca)Cu,0s, (R=Ce-Tm) are known to superconduct at
temperatures as high as T, =84 K. We have studied the relationship between superconductivity and
magnetism in the Ce and Pr analogs. In addition, we report the synthetic route and the magnetic
properties of the actinide analog Pb,Sr,(Cm/Ca)Cu,Os. The parent compound PbzSrzCmCu30s is
not a superconductor, but shows evidence of long range magnetic ordering at about 18 K. This is a
much higher temperature than is observed for any of the other R-ion parent compounds. These
results will be discussed in terms of the different hybridization and bonding properties of the 4f and
5 f electrons, and how these differences intluence superconductivity. These results will be compared
with the Pr and Cm analogs of the other superconducting series RBa,Cu307 and Rz-XThXCu04.
This work is supported by the U.S. DOE Basic Energy Sciences-Chemical
Sciences, under Contract No. W-31-109-ENG-38.
6740
J. Appl. Phys. 75 (IO), 15 May 1994
0021-8979/94/75(10)/6740/l
/$8.00
0 1994 American Institute of Physics
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