µSR Study on Antiferromagnetism of Alkali-Metal Clusters Incorporated in Zeolite Sodalite

Abstract

Na 4 3+ and K 4 3+ clusters arrayed in aluminosilicate sodalite are known to show antiferromagnetism below respective Néel temperatures T N =48 and ≃70 K. We newly prepared K–Rb alloy (K 3 Rb) 3+ clusters in addition to Na 4 3+ and K 4 3+ ones, and performed muon-spin relaxation (µSR) measurements. We find a large amplitude of precession signal in zero-field µSR spectra, indicating that antiferromagnetism takes place in the major volume of the samples. The T N is estimated from the temperature dependence of the precession signal to be ≃80 K for (K 3 Rb) 3+ . The internal field at the muon stopping site is estimated from the precession frequency to be ≃92, ≃142, and ≃155 Oe for Na 4 3+ , K 4 3+ , and (K 3 Rb) 3+ , respectively. Therefore, T N and the internal field are found to increase in the increasing order of atomic weight. These results are explained by the increase in the size of the s -electron wave function of clusters and the decrease in their potential depth.