Stress effect on coercivity of γ-Fe2O3 thin films

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Abstract
Thin Fe3O4 films were deposited in situ on Si(100) substrates by dc-reactive magnetron sputtering method, and then γ-Fe2O3 thin films were obtained by post-oxidation treatment. The effect of residual stress on coercivity of these films was studied by a bending-beam method. In situ stress-temperature curves of the films taken during the whole heat treatment processes revealed the magnitude and state of film stresses. The measured coercivity increments (470 Oe) are very close to the value (460 Oe) calculated based on stress-induced anisotropy for films with pure γ-Fe2O3 phase. For a film with mixed Fe3O4 and γ-Fe2O3 mixed phase, the magnetostriction is calculated to be 17×10−6. In situ stress-temperature data are provided to depict phase transformations and stress effects on the coercivity of such films.