Low-energy spin dynamics in the giant keplerate molecule { Mo72 Fe30 }: A muon spin relaxation and H1 NMR investigation

摘要: We present muon spin relaxation and $^{1}H$ NMR results on the magnetically frustrated keplerate molecule ${{\mathrm{Mo}}_{72}{\mathrm{Fe}}_{30}}$, aimed at studying local dynamics as a function of temperature. find that, in common with other molecular magnets, spectrum this material is characterized by single dominating electronic correlation time $\ensuremath{\tau}$. Experiments theory show that $\ensuremath{\tau}$ has thermally activated behavior an activation gap order energy difference between lowest-lying rotational bands material. This shows intermediate temperature range just above $1\phantom{\rule{0.3em}{0ex}}\mathrm{K}$, system occurs via Orbach processes involving levels belonging to two bands. Our data thus provide experimental estimate first interband gap.