Specific Heat of RBa2Cu3O7-x and RBaSrCu3O7-x Compounds (R = Sm, Dy, Er)
Z. Tarnawskia, N.-T.H. Kim-Nganb, X.Z. Wangc, V.H.M. Duijnd and J.J.M. Fransed
aSolid State Physics Dept., Faculty of Physics and Nuclear Technique, University of Mining and Metallurgy, Al. Mickiewicza 30, 30-059 Kraków, Poland
bInstitute of Physics and Informatics, Pedagogical University, Podchorążych 2, 30-084 Kraków, Poland
cAngewandte Physik, J. Kepler Universität, A-4040 Linz, Austria
dVan der Waals-Zeeman Laboratorium, Universiteit van Amsterdam, Valckenierstraat 65, 1018 XE Amsterdam, The Netherlands
Received: April 3, 1997; in final form November 5, 1997
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The low-temperature specific-heat C(T) data of high-Tc superconductors RBa2Cu3O7-x(R123O7-x) were reviewed. A discussion of the C(T) data obtained on single-crystalline samples of Er123O7-x and Sm123O7-x compounds in applied magnetic fields for better evaluation of the crystal-electric-field parameters is given. The C(T) measurements of Sr-substituted compounds RBaSrCu3O7 revealed the λ-type of peak related to the antiferromagnetic order at 1.2 K and 0.6 K respectively for Dy- and Er-compounds. The magnetic singlet ground state in these compounds is produced by weak exchange interactions of -0.05 T/μB and -0.035 T/μB, respectively. For Nd- and Sm-compounds, only a broad anomaly around 0.6 K was observed which is well fitted with a Schottky-type anomaly with an energy splitting of 1.4 K.
DOI: 10.12693/APhysPolA.93.513
PACS numbers: 74.70.-b, 75.40.-s