Ga NMR Study of the Local Susceptibility in Kagomé-BasedSrCr8Ga4O19: Pseudogap and Paramagnetic Defects

We present the first Ga(4f ) NMR study of the Cr susceptibility in the archetype of kagomé-based frustrated antiferromagnets, ${\mathrm{SrCr}}_8{\mathrm{Ga}}_4{\mathrm{O}}_{19}$. Our major finding is that the susceptibility of the frustrated lattice goes through a maximum around 50 K. Our data also support the existence of paramagnetic “clusters” of spins, responsible for the Curie behavior observed in the macroscopic susceptibility at low $T$. These results set novel features for the constantly debated physics of geometrically frustrated magnets.