Evidence of antiferromagnetic fluctuation in the unconventional superconductor λ -(BETS) 2GaCl4 by C 13 NMR

Abstract

We performed C13 NMR measurements on the unconventional organic superconductor λ-(BETS)2GaCl4 to clarify its electronic properties in the paramagnetic state. We found that the spin-lattice relaxation rate divided by temperature 1/T1T shows Curie-like enhancement above 55 K that arises from an antiferromagnetic fluctuation. In addition, we found additional enhancement of 1/T1T below 10 K, where the Knight shift decreases and the linewidth of NMR spectra is broadened. The result could be understood by the magnetic fluctuation induced by the nesting of the Fermi surface. We discovered that λ-(BETS)2GaCl4 salt inherently exhibits the two different types of magnetic fluctuations.