Interface exchange coupling induced enhancements in coercivity and maximal magnetic energy product of BaFe12O19/Co3O4 nanocomposites

Ferri/antiferromagnetic BaFe12O19/Co3O4 nanocomposites were prepared by annealing the compacted mixture of hydrothermal BaFe12O19 and Co(OH)2 nanoplates at 400 °C for 12 h. The microstructural characterization by XRD, FESEM/EDS, TEM, TG/DSC and Raman spectroscopy revealed that hexagonal Co(OH)2 was transformed into cubic Co3O4 spinel when co-annealed with ferrimagnetic BaFe12O19. This transformation, accompanied by a grain-refining process, produced homogeneously and intimately bound BaFe12O19/Co3O4 nanocomposite particles with a remarkable exchange bias field in the magnetization. Moreover, the coercivity and remanence of the BaFe12O19/Co3O4 nanocomposite with a mass ratio of 2:1 were enhanced by 26.1% and 25.2%, respectively, compared to the parent BaFe12O19 due to the strong interfacial exchange coupling interactions between the ferri- and antiferromagnetic phases. In addition, the maximal magnetic energy product of BaFe12O19 was also enhanced by 70.9%.