Effects of Fe3O4 underlayer on the annealing temperature of CoFe2O4 thin films

CoFe2O4 films of 100 nm thickness were deposited on 20 nm, rf magnetron‐sputtered Fe3O4 underlayers 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 Fe3O4 underlayers to 500 °C for films with underlayers. The decreased annealing temperature corresponds to a phase transformation of the Fe3O4 underlayers at about 400–500 °C, which accelerates the increase in grain size of the cobalt ferrite films. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)