The magnetic behavior of the ammoniated alkali fulleride (NH3)Rb3C60 is studied by means of μ+ spin relaxation (μ+SR) spectroscopy. The observation of a strongly damped oscillating component in the low-temperature zero-field μ+SR spectra reveals that its ground state is that of an ordered antiferromagnet, characterized by large spatially inhomogeneous effects. The temperature dependence of the μ+ spin precession frequency is consistent with that of a conventional 3D Heisenberg antiferromagnet (TN ∼ 51 K). The cooling rate of the sample affects sensitively the ordering of the magnetic moments, a behavior that can be attributed to the influence of the orientational order of the fullerene units on the exchange interactions.
ASJC Scopus subject areas