| Exchange Coupling and Spin-Flip Transition of CoFe2O4/alpha-Fe2O3 Bilayered Films (2002) | |||||||||
Abstract | |||||||||
| CoFe2O4/alpha-Fe2O3 (ferrimagnetic/antiferromagnetism) bilayered films were prepared on alpha-Al2O3(102) single-crystalline substrates by helicon plasma sputtering. A well-crystallized epitaxial alpha-Fe2O3(102) layer was formed on the substrate, while CoFe2O4 grown on alpha-Fe2O3(102) was a polycrystalline layer with a (100)-preferred orientation. The alpha-Fe2O3(102) films without CoFe2O4 layers clearly showed a spin-flip transition at about 400 K. The spins aligned perpendicular to the film plane at room temperature changed their direction within the film plane above 400 K. However the alpha-Fe2O3 base layers of CoFe2O4/alpha-Fe2O3 bilayered films did not show any spin-flip transition. The CoFe2O4 layer on alpha-Fe2O3 had a large in-plane magnetic anisotropy, while the spin axis of the alpha-Fe2O3(102) base layer was directed perpendicular to the film plane. The magnetization of ferrimagnetic CoFe2O4 layers was coupled perpendicularly to the spin axis of anitiferromagnetic alpha-Fe2O3 layers due to the exchange coupling at the interface between CoFe2O4 and alpha-Fe2O3. | |||||||||
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