Upper critical field in the electron-doped layered superconductor ZrNCl-0.7 : Magnetoresistance studies

Tou Hideki

Tanaka Y. J.

Sera M.

Taguchi Y.

Sasaki T.

Iwasa Y.

Zhu L.

Yamanaka Shoji

Physical review. B

We report magnetoresistance measurements of layered superconductor ZrNCl0.7 at high magnetic fields (H) as high as 27 T and temperatures (T) as low as 0.5 K. The T dependence of the upper critical field Hc2(T) for Hc and Hc was obtained. Hc2(T) starts to increase with a gentle slope near Tc(0) followed by a steep slope with decreasing T, implying the dimensional crossover of the interplane coherence length from three dimensional to two dimensional (2D). The Hc2(T) is found to be anisotropic for the field direction, where the slope of H=(dHc2/dT) near H1 T can be estimated as H–22.1 kOe/K and H–4.9 kOe/K for Hc and Hc, respectively. The obtained anisotropy parameter 4.5 gives evidence for the 2D characteristic of the superconducting state in ZrNCl0.7.

eng

The American Physical Society

Copyright (c) 2005 The American Physical Society

[ISSN] 1098-0121

[DOI] 10.1103/PhysRevB.72.020501

[DOI] http://dx.doi.org/10.1103/PhysRevB.72.020501