A local study of dynamic and static magnetism in the Kagome bilayer compound Ba2Sn2ZnCr6.8Ga3.2O22

We present a survey of an NMR and muSR magnetic study of the so called 'QS ferrite' frustrated antiferromagnet Ba2Sn2ZnCr6.8Ga3.2O22 (BSZCGO(0.97)). We compare our results to the archetype of highly frustrated magnets, SrCr8.6Ga3.4O19 (SCGO(0.95)), which has a very similar Kagome bilayer structure. These two compounds show a spin glass like transition at a temperature T-g, much lower than the Curie-Weiss temperature, despite a strong frustration of the Cr3+ (S = 3/2) Kagome bilayer lattice. Although there is a large difference between these transition temperatures, T-g (BSZCGO(0.97)) approximate to T-g (SCGO(0.95))/2.5, the evolution of the dynamics of the Cr3+ spins around T-g, as probed by muSR, is very similar in both samples, with a persistent dynamical magnetic ground state under approximate to0.4 T-g. This suggests that the spin glass like state and the dynamical properties are closely linked. A brief report of our NMR results is also given, where a maximum in the Cr bilayer susceptibility is observed around 45 K, similar to SCGO(p), and the existence of new dilution independent defects is evidenced.