Solvothermal synthesis and magnetic properties of BaFe_12−2x(NiTi)_xO₁₉ nanoparticles

M-type hexaferrites BaFe_12−2x(NiTi)_xO₁₉ (x=0, 0.05, 0.1, 0.3, 0.5, 0.7, and 0.9) were synthesized by the solvothermal method. X-ray diffraction (XRD) analysis reveals that the samples are of pure-phase with the space group of p6₃/mmc. As the Ni–Ti substitution level increases from x=0 to 0.9, the results of field-emission scanning electronic microscopy indicate that the particles are agglomerated and the mean particle size decreases. With the increase in substitution concentration x, the saturation magnetization increases first, and then declines slowly, whereas the coercivity decreases gradually. The variation of magnetic properties can be explained by the effects of Ni–Ti substitution. The results above indicate that our samples have positive effects on high density perpendicular recording. - Highlights: • It is the first time to synthesize the Ni–Ti substituted BaFe₁₂O₁₉ nanoparticles by solvothermal method. • The sizes of our sample decrease sharply to nanoscale with increasing x. • The Ni–Ti codoped samples not only can keep high M_s value effectively, but also can decrease the H_c drastically