Thermodynamic and Magnetotransport Properties of High Quality Na0.77CoO2 Single Crystals

A. Barana, A. Zorkovskáb, M. Kajňakovác, C.T. Lind and A. Feherc aDepartment of Physics, Faculty of Electrical Engineering and Informatics, Technical University of Košice, Park Komenského 2, 042 00 Košice, Slovakia bInstitute of Geotechnics, Slovak Academy of Sciences, Watsonova 45, 040 01 Košice, Slovakia cInstitute of Physics, Faculty of Science, P. J. Šafárik University, Park Angelinum 9, 041 54 Košice, Slovakia dMax-Planck-Institute for Solid State Research, Heisenbergstrasse 1, D- 70569 Stuttgart, Germany

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Heat capacity and electrical resistivity of high-quality Na0.77CoO2 single crystals was systematically studied as a function of temperature and magnetic field. Anomalies at 20 K have been observed both in the heat capacity and the electrical resistivity. The broad bump in the heat capacity indicates a smeared magnetic phase transition. Magnetic fields up to 9 T, oriented perpendicularly to the ab plane, reduce the temperature of this anomaly in accordance with the assumption of A-type antiferromagnetic ordering. The low temperature upturn observed in resistivity below 20 K for slow cooling is also suppressed by the magnetic field. This anomaly is probably the consequence of the interplay of several different mechanisms, including the Kondo effect, electron-electron interactions, and electron-phonon scattering.

DOI: 10.12693/APhysPolA.126.360 PACS numbers: 75.20.Hr, 75.40.Cx, 75.47.-m