Proton NMR measurements on the organic superconductor κ-(ET) 2Cu[N(CN)2]Br [where ET represents bis(ethylenedithio) tetrathiafulvalene] TC=11.6K exhibit stretched exponential spin-lattice relaxation below T≈25K, suggestive of an inhomogeneous magnetic phase that develops in the normal state and coexists with superconductivity. The onset of this phase coincides approximately with a large normal-state Nernst signal reported previously. By contrast, the closely related superconductor κ-(ET)2Cu(NCS)2 TC=10.5K shows single exponential spin-lattice relaxation and a conventional Nernst effect. The temperature range of TC < T < 30 K encompasses several phenomena in the κ-(ET)2X conductors, including changes in conduction-electron-spin resonance, electronic phase separation, and the onset of antiferromagnetic order. Analogous behavior in La2-xSr xCuO4 suggests that a spin glass or density wave may develop in κ-(ET)2Cu[N(CN)2]Br.
|Original language||English (US)|
|Journal||Physical Review B - Condensed Matter and Materials Physics|
|State||Published - Oct 14 2013|
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics