Cs133 and As75 NMR investigation of the normal metallic state of quasi-one-dimensional Cs2Cr3As3

We report Cs133 NMR and As75 nuclear quadrupole resonance (NQR) measurements on the normal metallic state above Tc of a quasi-one-dimensional superconductor Cs2Cr3As3 (Tc<1.6 K). From the Cs133 NMR Knight shift K133 measured at the Cs1 site, we show that the uniform spin susceptibility χspin increases from 295 K to ∼60 K, followed by a mild suppression; χspin then levels off below ∼10 K. In contrast, a vanishingly small magnitude of K133 indicates that Cs2 sites contribute very little to electrical conduction and the exchange interactions between 3d electrons at Cr sites. Low frequency Cr spin dynamics, reflected on As751/T1T (the nuclear spin-lattice relaxation rate 1/T1 divided by temperature T), shows an analogous trend as χspin. Comparison with the results of 1/T1T near Tc with K2Cr3As3 (Tc=6.1 K) and Rb2Cr3As3 (Tc=4.8 K) establishes a systematic trend that substitution of K+ ions with larger alkali ions progressively suppresses Cr spin fluctuations together with Tc.