Structural phase stabilization via Ba site doping with bivalent Sr, Ca and Zn ions and Fe site doping with trivalent Cr and Ga ions in the BaFe12O19 hexaferrite and its magnetic modification

Abstract

The doping of divalent Sr, Ca, and Zn ions at the Ba sites and trivalent Cr and Ga ions at the Fe sites in the M-type BaFe₁₂O₁₉ hexaferrite has been performed via the mechanical alloying of elemental metal oxides and post heat treatment. The structural phase in the material was studied by the analysis of the synchrotron X-ray diffraction patterns and Raman spectra. The doped samples show the M-type BaFe₁₂O₁₉ structure as the major phase and a small amount of hematite phase after heat treatment at 800 °C. This secondary phase was reduced at higher heat treatment temperatures. In addition to the M-type hexaferrite and hematite phases, the Zn-doped system-formed ZnFe₂O₄ and W-type hexaferrite after heat treatment at 800 °C and 1100 °C, respectively. The material shows a unique variation in crystallite size and lattice strain with the dopant and heat treatment of the samples. The X-ray photoelectron spectra confirmed that the charge states of the Fe site- (Fe, Ga, Cr) and Ba site- (Sr, Ca, Zn) doped ions are nearly +3 and +2, respectively. The hard ferrimagnetic properties of the BaFe₁₂O₁₉ structure have been retained in all the doped samples. The magnetic moment is noticeably changed by Fe site doping, unlike the small change noted with Ba site doping. The ferrimagnetic parameters of the samples are affected by the lattice structure regardless of whether metal doping is at the Ba and Fe sites of the M-type BaFe₁₂O₁₉ structure.