μSR study on ferrimagnetic properties of potassium clusters incorporated into low silica X zeolite

Potassium clusters are stabilized in the cages of low silica X zeolite, where the cages with the inside diameter of similar to 13 angstrom are arrayed in a diamond structure. The average number of potassium atoms per cage, n, is changed from similar to 6.3 to the saturated value of similar to 8.8 by controlling the guest potassium loading density. The temperature dependence of magnetization shows the typical behavior of the N-type ferrimagnetism at n similar to 6.8 and n similar to 8.3. The zero field mu SR spectra show significant increase in the relaxation rate below the Curie temperature, 5 K, in the sample with n similar to 6.8. The time dependence of asymmetry shows almost full amplitude of decrease, indicating that the internal field below the magnetic phase transition arises in the almost full volume of the sample. The longitudinal field mu SR spectra at 1.7 K show the typical decoupling behavior of a static internal field. A model of ferrimagnetism is proposed based on the structure of the zeolite, where a magnetic sublattice of itinerant electron ferromagnetism is assumed. (c) 2005 Elsevier B.V. All rights reserved.