  In this work, we demonstrate a massive intrinsic exchange bias (3 kOe) in
epitaxial CoFe2O4(111) thin films deposited on Al2O3(0001) substrates. This
exchange bias is indicative of intrinsic exchange or a ferromagnetic material
combined with an antiferromagnet. The analysis of structure, magnetism and
electronic states corroborate that there is an interfacial layer CoO between
the CoFe2O4(111) thin film and the Al2O3(0001) substrate. The power-law
thickness dependence of the intrinsic exchange bias verifies its interfacial
origin. This work suggests interfacial engineering can be an effective route
for achieving large exchange bias.
