119Sn solid-state NMR as a local probe for correlations in
Introduction
Triggered by investigations of electrical resistivity and specific heat identifying as a dense Kondo system, we performed solid-state NMR investigations on (hereafter referred to as Ce146) and the non-magnetic compound (La146) [1], [2], [3]. The absence of magnetic ordering indicates the dominance of the Kondo effect and suggests heavy fermion behavior [2]. In this paper, temperature-dependent NMR investigations on the 119Sn nuclei (Knight shift , spin–lattice relaxation rate ) of polycrystalline powder samples of Ce146 and La146 are presented.
Section snippets
Experimental
The investigated Ce146 sample was prepared by fixing randomly orientated microcrystals in paraffin. The material used here is from the same batch as that from Ref. [3]. Further details of sample preparation were reported elsewhere [3]. , ) NMR measurements were performed using a standard pulsed field sweep NMR spectrometer at a fixed frequency of MHz. The 119Sn NMR spectra for several temperatures were obtained by tracing the spin–echo intensity as a function
Results and discussion
Measurements of the magnetic susceptibility of Ce146 (not shown here) reveal local moment behavior at higher temperatures. Above , the susceptibility data are consistent with a Curie–Weiss behavior with an effective moment nearly equal to the free ion value. There is only a weak reduction of the moment at low temperatures. The results of the 119Sn field sweep NMR spectra of Ce146 and La146 observed at , 10 K and 100 K () are shown in Fig. 1. The linewidth for
Conclusions
119Sn field sweep spectra of show small and nearly constant . The temperature dependence of the spin–lattice relaxation rate exhibits semiconducting behavior down to with a gap value of . The low-temperature -upturn is interpreted as the formation of strong correlations around , which is consistent with specific heat measurements. We conclude that in , a correlated ground state forms out of a low-carrier density of states.
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