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

We present a survey of an NMR and μSR magnetic study of the so called 'QS ferrite' frustrated antiferromagnet Ba 2 Sn 2 ZnCr 6.8 Ga 3.2 O 22 (BSZCGO(0.97)). We compare our results to the archetype of highly frustrated magnets, SrCr 8.6 Ga 3.4 O 19 (SCGO(0.95)), which has a very similar Kagome bilayer structure. These two compounds show a spin glass like transition at a temperature Tg, much lower than the Curie-Weiss temperature, despite a strong frustration of the Cr 3+ (S = 3/2) Kagome bilayer lattice. Although there is a large difference between these transition temperatures, Tg (BSZCGO(0.97)) Tg (SCGO(0.95))/2.5, the evolution of the dynamics of the Cr 3+ spins around T g , as probed by μSR, is very similar in both samples, with a persistent dynamical magnetic ground state under 0.4T 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.