J. Phys. IV France 114 (2004) 285
The effect of magnetic ions and disorder on superconducting -(BEDT-TTF) 4[ (H 3O)M(C 2O 4) 3] C 6H 5NO 2 salts, where M = Ga and CrA.F. Bangura1, 1, A.I. Coldea1, A. Ardavan1, J. Singleton2, A. Akutsu-Sato3, H. Akutsu3 and P. Day3
1 Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX1 3PU, UK
2 National High Magnetic Field Laboratory, Los Alamos National Laboratory, TA-35, MS-E536, Los Alamos, NM 87545, USA
3 Davy-Faraday Research Laboratory, The Royal Institution, 21 Albemarle Street, London W1S 4BS, UK
We report magnetotransport measurements performed in magnetic fields of up to 33 T and at low temperatures (0.45 K <T <4.2 K) on two iso-structural superconducting charge-transfer salts, -(BEDT-TTF) 4[ (H 3O) M(C 2O 4) 3] C 6H 5NO 2, where the 3d metal ion M is either non-magnetic Ga 3+ or magnetic Cr 3+. Quantum oscillations suggest that the salt with M = Ga has two two-dimensional Fermi surface pockets (45 T and 230 T) whereas when M = Cr only one pocket (230 T) is observed. Replacing Ga with Cr has the effect of enhancing the effective mass of the 230 T pocket from to and reducing the superconducting critical temperature from Tc 8 K to Tc 5 K. Key words. organic superconductors-quantum oscillations.
© EDP Sciences 2004