Preparation of substituted barium ferrite BaFe 12−x(Ti 0.5Co 0.5) xO 19 by citrate precursor method and compositional dependence of their magnetic properties

Abstract

As a possible candidate for the left-handed metamaterial with negative permeability, a series of Ti, Co-substituted M-type barium hexaferrite BaFe 12− x (Ti 0.5Co 0.5) x O 19 ( x=0, 1, 2, 3, 4 and 5) was prepared by citrate precursor method. The formation processes of the substituted barium hexaferrite compounds from the precursors were followed by the measurements of powder X-ray diffraction (XRD), Infrared absorption spectra (FT-IR), and thermogravimetry and differential thermal analysis (TG/DTA) coupled with mass spectroscopy (MS). In the case of the non-substituted sample, the formation of the barium hexaferrite is regulated by the thermal decomposition of BaCO 3 and the solid-state reactions of BaO and Fe 2O 3 in the temperature range from 800 to 1100 K. The formation temperature of the substituted BaFe 12− x (Ti 0.5Co 0.5) x O 19 is higher than that for the non-substituted sample and increases with the value of x, due to the effects of carbonate ions incorporated by the partial substitution of Fe 3+ by (Ti 0.5Co 0.5) 3+. On heating up to ca. 1200 K, all the substituted samples transform into the magenetoplumbite phase as is the non-substituted sample. The compositional dependence of the magnetic properties of the substituted barium hexaferrite was investigated by the magnetization measurement. The decrease in the magnetic anisotropy was confirmed by the change in the magnetization curve and coercivity H C with the composition x. A negative permeability spectrum was observed in the BaFe 9(Ti 0.5Co 0.5) 3O 19 in the frequency range from 2 to 4 GHz.