Thin films of NiZn ferrite, Ni0.5Zn0.5Fe2O4, were formed on the substrate of quartz glass plate by rf magnetron sputtering by changing the substrate temperatures during the sputtering from 200 to 700 degrees C. The size of the NiZn ferrite crystallites composing the film was exhibited to be controlled from less than 10 nm to about 40 nm by the change of the substrate temperature. The formed nano-crystalline NiZn ferrite thin film with the crystalline size of similar to 40 nm showed constant magnetic permeability up to 2 GHz, indicating the possibility of nano-crystalline ferrite thin films as the materials for magnetic devices workable in GHz-frequency region. (C) 2010 Elsevier B.V. All rights reserved.