Unconventional upper- and lower-critical fields and normal-state magnetic susceptibility of the superconducting compound Na0.35CoO2•1.3H2O -: art. no. 132507

Magnetic properties of the layered superconductor, Na0.35CoO2.1.3H(2)O have been investigated. From the temperature dependence and field dependence of the magnetization, the superconducting transition temperature, as well as upper- and lower-critical fields have been estimated to be T-C=4.6 K, H-C2(0)=61.0 T and H-C1(0)=28.1 Oe, respectively. These values give quite unusual phenomenological parameters, i.e., coherent length, penetration depth and Ginzburg-Landau parameter of xi=2.32 nm, lambda=5.68x10(2) nm, and kappaequivalent tolambda/xi=244, respectively, suggesting an unconventional nature of superconductivity. Additionally, the magnetic susceptibility above T-C and the magnetization curve up to 54 T are also reported.