Exchange anisotropy in epitaxial Fe3O4/CoO and Fe3O4/COxFe3-xO4 bilayers grown by pulsed laser deposition

Magnetic exchange anisotropy has been studied in epitaxial Fe3O4 based bila yers grown by pulsed laser deposition on MgO substrates. Measurements of th e exchange biasing of the Fe3O4 magnetization curves were performed on (100 )- and (111)-oriented Fe3O4 (20 nm)/CoO (20 nm) bilayers and (100)-oriented Co0.16Fe2.84O4 (190 nm)/Fe3O4 (40-370 nm) bilayers. The effective exchange bias field H-eb and coupling energy were found to be 10-10(2) kA/m and 1-2 mJ/m(2), respectively. The dependence of H-eb on the thickness d of the so ft magnetic component (magnetite) of the cobalt ferrite/magnetite bilayer H (eb)similar to 1/d is found to be in agreement with the predictions of a St oner-Wohlfarth-type model. The order of magnitude and the temperature depen dence of H-eb for the Fe3O4/CoO bilayers are similar to those of bilayers p repared by molecular beam epitaxy. (C) 1998 American Institute of Physics. [S0021-8979(98)09420-1].