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TT: Tiefe Temperaturen
TT 7: Postersitzung I: Anwendungen der Supraleitung (1-6), Dünne Schichten, Josephsonkontakte, SQUIDs (7-17), Neue und unkonv. Supraleiter(18-23), Amorphe- und Tunnelsyst. (24-28), Quantenflüssigkeiten (29-30), Syst. korr. Elektr.: Theorie I (31-45)
TT 7.20: Poster
Monday, March 11, 2002, 14:30–18:00, A
Evidence of reentrant superconductivity in a diluted Van Vleck paramagnet — •Thomas Herrmannsdoerfer and Frank Pobell — Forschungszentrum Rossendorf, Postfach 51 01 19, D-01314 Dresden
Compared to magnetically doped superconductors described by the theory of Abrikosov and Gorkov [1], electronic singlet ground state systems can have a much larger critical concentration of magnetic impurities [2]. Recent measurements on the quasi binary Van Vleck paramagnet La1−xPrxTe revealed a critical Pr3+ concentration x close above 0.50. Surprisingly, in La0.50Pr0.50Te the superconducting state with Tc = 0.20 K is not stable down to zero temperature but undergoes a reentrant transition at about 0.02 K. This reentrant transition is likely caused by the hyperfine enhanced magnetic moments of the 141Pr nuclei. Although the hyperfine enhanced nuclear moments are not in a magnetically ordered ground state at T = 0.02 K, their impact on superconductivity seems to be even stronger than the influence of a nuclear ferromagnetic phase transition on type-I superconductivity observed in AuIn2 [3]. [1]A. Abrikosov and L. Gorkov, Sov. Phys. JETP 12, 1243 (1961) [2]J. Keller and P. Fulde, J. Low Temp. Phys. 4, 289 (1971) [3]S. Rehmann, T. Herrmannsdoerfer and F. Pobell, Phys. Rev. Lett. 78, 1122 (1997)