Effects of Fe3O4underlayer on the annealing temperature of CoFe2O4thin films

CoFe2O4films of 100 nm thickness were deposited on 20 nm, rf magnetronsputtered Fe3O4underlayers on naturally oxidized Si 100 substrates. These films were then annealed, and the magnetic properties and microstructures were investigated as a function of annealing temperature. Results show that the optimum annealing temperature to obtain the maximum coercivity decreases from 700 °C for films without Fe3O4underlayers to 500 °C for films with underlayers. The decreased annealing temperature corresponds to a phase transformation of the Fe3O4underlayers at about 400–500 °C, which accelerates the increase in grain size of the cobalt ferrite films. © 2009 WILEYVCH Verlag GmbH & Co. KGaA, Weinheim