Effect of Ni(OH)2 coating on the electromagnetic properties of hexagonal barium ferrite

Barium ferrite (BaF), BaFe12O19, was successfully prepared by a sol-gel self-propagating high-temperature synthesis (SHS) method, and the BaF sample was coated with nickel hydroxide through a coordination-precipitation method (Ni(OH)2/BaF). Nickel hydroxide was determined in Ni(OH)2/BaF by energy dispersive X-ray analysis (EDAX), though no diffraction peaks of nickel hydroxide was detected by XRD. BaF and Ni(OH)2/BaF both show single magnetic domain characteristics, while sample Ni(OH)2/BaF displays slight decrease in saturation magnetization, remanent magnetization, coercivity, and magnetocrystalline anisotropy constant, due to paramagnetic property of nickel hydroxide and reduction in surface anisotropy upon coating. The reflection loss of BaF particles in 2-18 GHz was essentially enhanced upon nickel hydroxide coating, which was expected to result from the great enhancement of complex permittivity and improved matched characteristic impedance of the free space.