Exchange Bias Effect in CoO@Fe₃O₄ Core–Shell Octahedron-Shaped Nanoparticles

Increased coercive and tunable exchange bias field values were registered in hybrid CoO@Fe₃O₄ core–shell octahedron-shaped nanoparticles of different average size. In this strained morphology, the metal cation chemical potentials at the interface between the antiferromagnetic and ferrimagnetic oxides become a very dynamic variable. This causes the effective magnetic anisotropy to increase and the type of interface to change after growing the magnetite shell epitaxially onto the cobalt oxide {111} surface facets and, consequently, to tune the exchange bias effect