$\mu$SR Study on Antiferromagnetism of Alkali-Metal Clusters Incorporated in Zeolite Sodalite

概要

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Na43+ and K43+ clusters arrayed in aluminosilicate sodalite are known to show antiferromagnetism below respective Néel temperatures $T_{\text{N}}=48$ and ${\simeq}70$ K. We newly prepared K–Rb alloy (K3Rb)3+ clusters in addition to Na43+ and K43+ ones, and performed muon-spin relaxation ($\mu$SR) measurements. We find a large amplitude of precession signal in zero-field $\mu$SR spectra, indicating that antiferromagnetism takes place in the major volume of the samples. The $T_{\text{N}}$ is estimated from the temperature dependence of the precession signal to be ${\simeq}80$ K for (K3Rb)3+. The internal field at the muon stopping site is estimated from the precession frequency to be ${\simeq}92$, ${\simeq}142$, and ${\simeq}155$ Oe for Na43+, K43+, and (K3Rb)3+, respectively. Therefore, $T_{\text{N}}$ 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.
2010-07-15