Fine magnetic particles in layered silicates and zeolites

Ultrafine Ni particles have been generated at ambient temperatures in clay (montmorillonite) and zeolite (mordenite) matrices. The synthesis involves a reduction in aqueous solutions of the ion-exchanged clay or zeolite with sodium borohydride. SQUID magnetometer measurements reveal single domain Ni particles with superparamagnetic properties. While the Ni particles in clay have a narrow distribution of blocking temperatures T_b and particle size, they seem to have in zeolites a broader distribution of T_b and particle size. Time decay measurements of thermoremanent magnetization also support single domain characteristics