An exchange bias effect was observed in the field cooling of epitaxial magnetite, Fe3O4, films on MgO (100) substrates. This effect was attributed to the presence of antiphase boundaries. The magnitude of the exchange bias field depended strongly upon the thermomagnetic history of the sample. The strength of the exchange bias field was found to increase with increasing film thickness and was attributed to the strain-driven redistribution of atoms in the vicinity of antiphase boundaries; leading to enhanced antiferromagnetic exchange interactions.

Antiphase Boundaries Induced Exchange Coupling in Epitaxial Fe3O4 Thin Films. S.K.Arora, R.G.S.Sofin, A.Nolan, I.V.Shvets: Journal of Magnetism and Magnetic Materials, 2005, 286, 463-7