Ferromagnetism of potassium clusters incorporated into zeolite LTA

Potassium clusters are incorporated into supercages of zeolite LTA crystals, with the supercages arrayed in a simple cubic structure at a number density of 5.3×${10}^{20}$ ${\mathrm{cm}}^{\mathrm{-}3}$. About four 4s electrons of K atoms are included in each cluster. The ac magnetic susceptibility increases dramatically with decreases in temperature below 8 K, and shows ferromagnetism below about 4 K. The effective magnetic moment per supercage is estimated to be about 0.13${\mathrm{\mu }}_{\mathit{B}}$ at 1.7 K. Magnetic properties resemble those of a reentrant spin glass.