One-step hydrothermal synthesis and characterization of high magnetization CoFe2O4/Co0.7Fe0.3 nanocomposite permanent magnets

Abstract: CoFe2O4/Co0.7Fe0.3 nanocomposite permanent magnets have been synthesized in one step by a hydrothermal method at reaction temperatures of 80, 120, 140, 160 and 180°C and characterized by XRD, SQUID, SEM, (HR)TEM, and SAED. All samples consisted of octahedral CoFe2O4 particles and spherical-like Co0.7Fe0.3 particles. The maximum magnetization and coercivity were 191emu/g and 1311Oe, respectively, values not previously observed for the CoFe2O4/Co0.7Fe0.3 system. This maximum magnetization was attributable to the larger mass ratio of Co0.7Fe0.3 to CoFe2O4, which were in intimate contact. Magnetic dipolar interaction plays a crucial role in magnetic properties and leads to the reduction of the magnetization and the Mr /Ms ratio. The coercivity of all samples exhibited complex variation with reaction temperature and its mechanism may deserve further investigation. [Copyright &y& Elsevier]