Doping effect on crystal structure and magnetic properties of chromium-substituted strontium hexaferrite nanoparticles

Chromium-substituted hexagonal strontium ferrite, SrFe12−xCrxO19 (x=0-1.0), nanoparticles were prepared by the chemical sol-gel route for high-density magnetic recording, and the characteristic of structure and magnetism dependence of the Cr doping is investigated. For suitable doping (x⩽0.4), the values of specific saturation magnetization do not decrease and slightly increase, but coercivity decreases. This substituted particle is suitable for high-density magnetic recording. Structural analysis has shown that the samples still remain a hexagonal magnetoplumbite phase in x=0-0.4 and the non-magnetic phase, α-Fe2O3, appears after x=0.6, and that the change of the main axis (c-axis) in hexaferrite is larger than that of a-axis for the substitution with Cr3+ ion. Magnetic measurements have revealed that the Hopkinson effect was related to crystal structure and magnetism, and that doping also influences the Hopkinson effect, where the values of peaks decrease and the peak-width broadens as doping increases.