Bimagnetic CoO Core/CoFe2O4 Shell Nanoparticles: Synthesis and Magnetic Properties

In this work we report on the synthesis, the microstructural characterization, and the magnetic properties of similar to 7 nm bimagnetic core/shell nanoparticles prepared by seed-mediated growth high temperature decomposition of organometallic precursor. The nanoparticles are formed by an antiferromagnetic CoO core coated with ferromagnetic CoFe2O4 shell of 2-3 run of thickness. XRD and electron diffraction patterns show the reflections of the structure of the CoFe2O4 and CoO phases and Dark- and Bright-field TEM images provide evidence of the core shell morphology of the system. Magnetic measurements show that the system presents a remarkably large coercivity and high squareness (at 5 K, Hc = 27.8 kOe and M-r/M-s = 0.79), compared to CoFe2O4 single phase nanoparticles of comparable size. The enhancement of the effective anisotropy is attributed to the surface and interface exchange coupling effects.