Magnetic properties of exchange-coupled Fe/FeO bilayers

The magnetic, structural and microstructural properties of sputtered Fe thin films and Fe/Fe-O bilayers were studied as a function of the Fe layer thickness, the type of the Fe oxide and the substrate used. Two different ways to prepare the oxide layers were used; postdeposition oxidation nd reactive sputtering. Postdeposition oxidation produced films with mixed Fe-oxides (FeO, Fe3O4, Fe2O3); however reactive sputtering led to bilayers with controlled stoichiometry, Fe/FeO, Fe/Fe3O4, and Fe/Fe2O3, respectively. The coercivity of both the Fe films and Fe/Fe-O bilayers, deposited on substrates with or without Cr buffer layer, was found to increase with decreasing Fe film thickness. The coercivity of the samples deposited on a Ag buffer layer was much lower and did not change substantially with the Fe film thickness. The presence of the Fe-oxide layer led to a large increase of coercivity. This is attributed to the higher anisotropy of the oxide and to exchange coupling of Fe-oxide with the softer Fe layer. (C) 1996 American Institute of Physics.