An NMR approach to the superconducting regime of the spin ladder compound Sr2Ca12Cu24O41
Laboratoire de Physique des Solides (associé au CNRS) , Université Paris-Sud, 91405 Orsay Cedex,
2 Laboratoire de Physicochimie des Solides (UMR 8648) , Université Paris-Sud, 91405 Orsay Cedex, France
3 II. Physikalisches Institut, Universität zu Köln, Zülpicher Str. 77, 50937 Köln, Germany
Published online: 15 February 2000
63Cu-NMR experiments of Knight shift and relaxation time T1 have been performed on the two-leg spin ladders of a Sr2Ca12Cu24O41 single crystal at several pressures up to the critical pressure Pc for the stabilization of a superconducting ground state. The data confirm the onset of low-lying spin excitations at Pc observed previously [Science 279, 345 (1998)] and reveal a marked decrease of the spin gap under pressures above 20 kbar although a significant fraction of the spin excitations remains gapped at kbar. A comparison between NMR and transport data under pressure suggests that the depression of the spin gap can be ascribed to an increase in the interladder exchange coupling, possibly mediated by the ladder-chain interaction along the b-direction.
PACS: 74.72.Jt – Other cuprates / 74.25.Ha – Magnetic properties
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag, 2000