Evidence for ferromagnetism in rubidium clusters incorporated into zeolite A

Magnetic properties are studied on Rb clusters generated in the cages of zeolite A (framework type code LTA), where the cages with an inside diameter of similar to 11 angstrom are arrayed in a simple cubic structure. When the average number of s-electrons per cluster, n, is larger than similar to 4, ferromagnetic properties are newly observed at low temperatures. The Curie temperature is estimated to be similar to 3.5K at n = 5.0 from the Arrott-plot analysis. The magnetic susceptibility shows Curie-Weiss law with a negative Weiss temperature, T-W, of about -25K, indicating that the coupling between magnetic moments of clusters is antiferromagnetic. Possible origins of the ferromagnetism in Rb clusters are discussed. (c) 2006 Elsevier B.V. All rights reserved.