FERROMAGNETIC PROPERTIES OF POTASSIUM CLUSTERS INCORPORATED INTO ZEOLITE LTA

Ferromagnetic properties are reported for K clusters incorporated into the alpha cage (supercage) of zeolite LTA. In LTA, alpha cages are arrayed in a simple cubic structure with a lattice constant of 12.3 angstrom. The average 4s-electron number per cluster, n, is systematically changed from 0.8 to 7.3 by controlling the K loading density. Ferromagnetism is observed for 2 - 3 < n < 6- 7. The magnetization shows a peak at n approximately 5, and the average magnetic moment amounts to 0. 24 mu(B) per cluster at 100 Oe and 1.7 K. The Curie temperature is n dependent and less than 7 K. Magnetic properties are basically interpreted in terms of the model of itinerant electron ferromagnetism. Narrow energy bands due to the electron transfer between adjacent clusters play an important role in the construction of a model. The magnetic properties exhibit spin-glass and reentrant spin-glass phenomena depending on the K loading density.