Strong perpendicular exchange bias was realized in sputter-deposited CoPt/CoO multilayers. The as-deposited multilayer shows strong perpendicular magnetic anisotropy (PMA) which remains up to a critical CoPt layer thickness as thick as 4 nm. After perpendicular field cooling, the multilayer with antiferromagnetic CoO and ferromagnetic CoPt interfaces exhibits large perpendicular exchange bias of 1730 Oe. Strong PMA in the CoPt/CoO multilayer is mainly attributed to the positive magnetoelastic energy due to the remarkable in-plane tensile stress originating from the local epitaxial growth. The mechanism for the exchange bias was explained in terms of the interfacial spin structure.
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