Numéro
J. Phys. IV France
Volume 114, April 2004
Page(s) 401 - 402
DOI https://doi.org/10.1051/jp4:2004114097


J. Phys. IV France
114 (2004) 401
DOI: 10.1051/jp4:2004114097

Cooling rate dependence of the in-plane magnetic penetration depth in $\kappa $-type BEDT-TTF superconductors

N. Yoneyama1, 1, A. Higashihara1, T. Sasaki1, T. Nojima2 and N. Kobayashi2

1  Institute for Materials Research, Tohoku University, Katahira 2-1-1, Aoba-ku, Sendai 980-8577, Japan
2  Center for Low Temperature Science, Tohoku University, Katahira 2-1-1, Aoba-ku, Sendai 980-8577, Japan


Abstract
We performed dc magnetization measurements under the control of cooling-rate in the organic superconductors $\kappa $-(BEDT-TTF) 2X ( X=Cu(NCS) 2 and Cu[ N(CN) 2] Br). A distinct different cooling-rate dependence of the in-plane magnetic penetration depth ( $\lambda $ //(0)) was observed between two salts, where $\lambda $ //(0) was estimated from a linear extrapolation to 0 K. In the Cu(NCS) 2 salt, $\lambda $ //(0) remains unchanged regardless of cooling-rate, while Tc decreases slightly in faster-cooling. On the other hand, $\lambda $ //(0) in the Cu[ N(CN) 2] Br salt becomes long significantly in faster-cooling. We quantitatively explain the change of $\lambda $ //(0) in the cooling-rate as an impurity effect by terminal ethylene disorder in BEDT-TTF molecules in terms of the local and clean limit approximation. Key words. Organic superconductor, magnetization, penetration depth, London model.



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