Submicron particles of Ga-substituted strontium hexaferrite obtained by a citrate auto-combustion method

Abstract

In this study, we demonstrate the synthesis and the investigation of the magnetostatic and magnetodynamic properties of single-domain gallium substituted strontium M-type hexaferrite particles SrFe_12−xGa_xO₁₉ (x = 1–6). The synthetic approach is based on a precursor preparation via a facile citrate–nitrate auto-combustion method followed by thermal treatment at 1200 °C. The annealing of the porous precursor led to the formation of single-domain hexaferrite particles with mean sizes of 360–560 nm. Introduction of Ga³⁺ ions up to x = 4 into the hexaferrite structure resulted in an increase of coercivity from 5.1 to 6.4 kOe, and a further increase in gallium concentration led to a decrease in the coercivity. The samples display natural ferromagnetic resonance frequency in the range of 49–57 GHz. Crystal structure refinement reveals that Ga³⁺ ions preferably occupy 2a, 4f₁, 12k, and 2b sites and cause a decrease in the magnetic anisotropy and a modest decrease in the saturation magnetization.