Morphology, crystal structure and XPS depth profiling study of Ni-Zr co-doped M-type Sr-ferrite and adjustment of their magnetic properties

SrFe_12–2xNi_xZr_xO₁₉ (x = 0–0.9) ferrites were successfully synthesized through hydrothermal method using metal chloride as start materials. It exhibits very good hexagonal crystals with doping content x < 0.3, but deviate from hexagonal flakes with increasing doping, accompanied by some debris. XRD confirm that the impurity phase decrease with the increase of doping amount even though the sample annealed at 950 °C. After annealing at 1150 °C, It exhibits the absence of secondary phases of SrCO₃. It was found the obvious preferred orientation and becomes more significant with the increase of doping amount. In addition, the deconvoluted XPS of Sr 3d and Zr 3d indicated the complexed coordination with high doping amount x > 0.5. Magnetic properties further validated the ions migration and multielectron transitions. The highest saturation magnetization value observed is 55.66 emu/g for the x = 0.3 sample. With dopant increasing, the coercivity decreases steadily from 840 to 190 Oe. Thus, the materials with high Ms and low Hc values could be suitable used in longitudinal magnetic recording media.