A study of magnetoplumbite-type (M-type) cobalt–titanium-substituted barium ferrite, BaCoxTixFe12−2xO19 (x = 1–6)

Cobalt(II)–titanium(IV)-substituted barium ferrite forming the chemical formula of BaCoxTixFe12−2xO19 (x = 1–6) have been investigated using X-ray diffraction spectroscopy (XRD), Superconducting Quantum Interference Device (SQUID) and high-resolution transmission electron microscopy (HRTEM). The specimen of magnetoplumbite (M-type) Co–Ti-substituted BaFe12O19 were synthesised via sol–gel method using ethylene glycol as precursor. Significant increase in line broadening of the XRD patterns were observed indicating the decrease of particle sizes due to the Co(II)–Ti(IV) substitution. BaCo3Ti3Fe6O19 showed the highest coercivity but moderate saturation and remnant magnetisations. HRTEM imaging showed that Co(II)–Ti(IV) substitution in the system of BaCoxTixFe12−2xO19 (x = 1–6) produced no drastic change in the structure of the M-type ferrites. Most of the M-types crystals examined by HRTEM displayed a long axis perpendicular to the c-axis of the M-type structure. Disordered crystals showing the intergrowth between Co–Ti-substituted barium ferrite and the spinel-structured iron oxide were detected.