Synthesis and Magnetic Properties of Ferrimagnetic CoFe₂O₄ Nanoparticles Embedded in an Antiferromagnetic NiO Matrix

Abstract

Ultrafine cobalt ferrite nanoparticles were prepared by forced hydrolysis in diethyleneglycol and, after centrifugation, dispersed in the same solvent to form a sol in which a layered hydroxyacetate nickel salt was precipitated. The as-obtained composite was moderately calcined in air to form nanoparticles constituted by a ferrimagnetic CoFe2O4 core embedded in well-crystallized antiferromagnetic NiO. Magnetic properties such as coercivity, hysteresis loop shift, and blocking temperature were analyzed regarding exchange bias features by comparing the magnetic data measured on these particles to those obtained on fresh CoFe2O4 particles mechanically dispersed in a diamagnetic Al2O3 matrix.