AGING EFFECT ON COERCIVITY OF IRON-OXIDE THIN-FILMS

Changes in magnetic properties for Fe3-xsquarexO4 (X: oxidation degree ) thin films made by reactive sputtering and subsequent heat treatment s have been examined under room temperature aging and constant tempera ture annealing. Aging causes variations in coercivity of insufficientl y oxidized films which have a specific resistance of less than 1 x 10( 1) OMEGA . cm, while the coercivity of gamma-Fe2O3 (X = 1/3) did not c hange. This phenomenon did not depend on additive elements or preparat ion method. Other magnetic properties such as saturation magnetization , residual magnetization, squareness ratio and coercive squareness, we re not affected by aging for any Fe3-xsquarexO4 composition. The activ ation energy for a coercivity change is 0.72-0.95 eV near room tempera ture for films with a specific resistance below 1 X 10(1) OMEGA . cm. It was confirmed that only the coercivity varied at 20-degrees-C, whil e both coercivity and the degree of oxidation changed with annealing a t 100-degrees-C.