J. Phys. IV France
Volume 114, April 2004
Page(s) 199 - 203

J. Phys. IV France
114 (2004) 199
DOI: 10.1051/jp4:2004114044

The effect of pressure on the phase diagram of the magnetic field-induced superconducting state of $\lambda
$ -(BETS) 2FeCl 4

L. Balicas1, 1, V. Barzykin2, K. Storr1, 3, J.S. Brooks1, M. Tokumoto4, S. Uji5, H. Tanaka6, H. Kobayashi6 and A. Kobayashi7

1  National High Magnetic Field Laboratory, Florida State University, Tallahassee, FL 32306, USA
2  Department of Physics, University of Tennessee, Knoxville, TN 37996-1200, USA
3  Physics Department, Florida A&M University, Tallahassee, FL 32307, USA
4  Nanotechnology Research Institute, Tsukuba, Ibaraki 305-8568, Japan
5  National Research Institute for Metals, Tsukuba, Ibaraki 305-0003, Japan
6  Institute for Molecular Science, Okazaki, Aichi 444-8585, Japan
7  Research Centre for Spectrochemistry, The University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan

We report the effect of a small hydrostatic pressure p $\cong $ 1.4 kBar on the temperature-magnetic field phase diagram of the organic conductor $\lambda
$-(BETS) 2FeCl 4. At zero field a first-order superconducting ( $T_{C} \cong $ 5.6 K) to antiferromagnetic insulator transition ( $T_{N} \cong $ 4 K) is observed. The close proximity between both phases is suggestive of an unconventional superconducting pairing mechanism. Furthermore, the transition temperature towards the field-induced superconducting state (FISC), as well as its concomitant upper critical field, is found to increase by a factor of $\sim $ 33 %. The phase diagram of the FISC state for both p = 1 Bar and 1.4 kBar are well described in terms of the Jaccarino-Peter effect if the quasiparticle nature of the charge carriers is taken into account. Key words. Organic conductors - magnetism - superconductivity.

© EDP Sciences 2004