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Superconductivity of κ-(BEDT–TTF)2 Cu[N(CN) 2]Br: Isotope Effect Revisited

Published online by Cambridge University Press:  10 February 2011

M. Tokumoto ,
N. Kinoshita ,
Y. Tanaka  and
H. Anzai
M. Tokumoto
Affiliation:
Electrotechnical Laboratory, Tsukuba, Ibaraki 305, Japan, [email protected]
N. Kinoshita
Affiliation:
Electrotechnical Laboratory, Tsukuba, Ibaraki 305, Japan, [email protected]
Y. Tanaka
Affiliation:
Electrotechnical Laboratory, Tsukuba, Ibaraki 305, Japan, [email protected]
H. Anzai
Affiliation:
Himeji Institute of Technology, Kamigori, Hyogo 678–12, Japan
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Abstract

In 1991, we reported a normal isotope effect in organic superconductor κ-(BEDT–TTF)2Cu[N(CN)2]Br, when all the hydrogen atoms of BEDT – TTF were replaced with deuterium. In other words, Tc was depressed by as much as 0.9 K, in contrast to the “inverse isotope effect” commonly observed in 10K-class organic superconductors. Recently, it was reported that the deuterated κ-(BEDT–TTF)2Cu[N(CN)2]Br shows an insulating nature when cooled very rapidly. Therefore, it is necessary for us to reexamine the superconducting transition of both deuterated and undeuterated κ- (BEDT – TTF)2Cu[N(CN)2]Br by SQUID measurements with special attention to the cooling speed. We studied the effect of cooling rate ranging from 10 K/min down to as slow as 0.02 K/min, and observed a significant effect not only on the superconducting transition temperature Tc but also on the superconducting volume fraction.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 488: Symposium J – Electrical, Optical & Magnetic Properties of Organic IV , 1997 , 903
Copyright
Copyright © Materials Research Society 1998

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