Magnetic properties of Na-K clusters in low-silica X zeolite doped by pressure loading

Low-silica X (LSX) zeolite has the FAU-type framework structure constructed of supercages and beta-cages with effective inside diameters of 13 and 7 angstrom, respectively. Respective cages are arrayed in a diamond structure. Na-K clusters are formed by the loading of guest potassium atoms nK into LSX, where the unloaded LSX has 4Na and 8K zeolite-cations per supercage (or beta-cage) as given by Na4K8Al12Si12O48. N-type ferrimagnetism has been observed at ambient loading densities of K atoms, 6.5 < n < 8.5. Ferrimagnetism was not observed at the maximum loading density at ambient pressure, n approximate to 9. In the present study, we extended the loading density for 9 < n by the pressure-loading technique. Spontaneous magnetization is observed again below 10.5 and 9.1 K at the loading pressures approximate to 400 and approximate to 520 MPa respectively. Respective Weiss temperatures are -23 and -32 K. These results indicate that the ferrimagnetism appears again at higher loading densities.