Synthesis and magnetic properties of Co–Cr2O3 nanocomposites

Abstract Co:Cr 2 O 3 nanocomposites were prepared with phase separated metallic Co clusters in a wide range of concentrations namely 10, 20, 30, 40 and 50 wt% Co. Samples were annealed at different temperatures to study the effects of crystallization of Cr 2 O 3 and the growth of Co metal clusters on the magnetic behavior of nanocomposites. Enhanced crystallinity of antiferromagnetic (Cr 2 O 3 ) matrix and growth of Co clusters with higher annealing temperatures strongly affects the coercivity, saturation and magnetic viscosity in these hybrid materials. Amorphous Cr 2 O 3 acts as a paramagnetic matrix for Co particles. Exchange anisotropy stabilizes magnetic moments of Co embedded in Cr 2 O 3 only if Cr 2 O 3 is crystalline. This exchange anisotropy leads to the enhancement of coercivity. Relaxation measurements confirm that exchange anisotropy is higher for samples with lower Co content.