Temperature Dependence of the Critical Field of the Organic Superconductor κ-(BEDT-TTF)2Cu[N(CN)2]Br
Résumé
We present upper critical magnetic fields data for κ(BEDT-TTF)2Cu[N(CN)2]Br (hereafter k-Br), single crystals with the magnetic field applied either or perpendicular and parallel to the conducting layers. The H-T phase diagram in these single crystals has been deduced from tunnel diode oscillator-based contactless measurements in pulsed magnetic fields up to 56 T for the inter-plane ( H ∥ b) and in-plane ( H ∥ ac) field directions. Temperature dependence of the magnetic penetration depth in DC fields is also reported. The temperature dependence of the upper critical magnetic field H c2( T) is not accounted for the Werthamer-Helfand-Hohenberg model for in-plane configuration. For the inter-plane orientation, a significant upward curvature is observed as the temperature decreases, in the range close to T c , followed by saturation at lower temperatures. Possibly, this upturn is an indication of flux-line lattice melting.