We performed μSR experiments on rubidium clusters arrayed in porous crystals of zeolite A.
These clusters are known to show spontaneous magnetization of ferromagnetism at higher
loading densities of Rb atoms in a previous study. The development of the internal field is
observed below≃ 4K in the temperature dependence of zero-field μSR spectra in the
sample n= 5.8, where n is the average loading density of Rb atoms per unit cage. The Curie
temperature of this sample is estimated to be≃ 5K from the Arrott plot analysis. The ...