In this paper,Fe3O4/α-Fe2O3 core-shell structures were prepared by solid phase oxidation reaction from Fe3O4 particles,and field cooling was carried out at a high magnetic field(1T)lower than antiferromagnetic Neel temperature(955 K).The crystal structure,microstructure and magnetic properties of Fe3O4/α-Fe2O3 core-shell structures were measured and analyzed.It is found that the coercivity of the particles increases from about 57 Oe to 4 525 Oe and that the hysteresis loop exhibits a wasp-waisted shape with the increase of the antiferro-magnetic layer α-Fe2O3 thickness on the surface of ferrimagnetic Fe3O4.When the thickness of the antiferromag-netic layer is about 533 nm,the hysteresis loop shows the enhanced exchange bias field of～601 Oe.The theoret-ical calculation shows that the exchange bias of the ferrimagnetic/antiferromagnetic core-shell microstructures is enhanced due to the ferromagnetic interaction at the interfaces.The anisotropy energy and Zeeman energy of the core-shell structures higher than the interfacial exchange energy,respectively,dominates the exchange bias when the antiferromagnetic thickness is higher than 510 nm.
万方数据