Figure 3
(a) Representative temperature dependences of 23Na 1/T1T for the SC/ZC component with shorter relaxation time. The solid lines are fits obtained from the BPP model described by Eq. (1). We obtain Ea = (94, 90, 132) meV, τ0 = (5.8, 15, 1.7) × 10−12 s and C = (13, 8.8, 9.4) × 1012 s−2 for n = (11.6, 14.4, 16.4), respectively. (b) Low-temperature dependences of 23Na 1/T1T showing plateau-like behaviour below 25 K for various loading levels n. The solids lines are fits obtained by combining the BPP and Korringa relaxation mechanisms [Eq. (3)]. For comparison we added the low-temperature data for the n = 9.4 sample, which is according to the optical reflectance and resistivity measurements considered to lie deep in the insulating phase.
