In this paper, Bi³⁺ ion-doped Ni–Mg–Co ferrite nanomagnetic materials were prepared by sol–gel auto-combustion method using high-purity nitrates and citric acid experimental materials. The effect of Bi³⁺ ion content on the lattice structure and magnetic properties of nanoferrite was also studied. XRD diffractogram analysis shows that the Ni–Mg–Co ferrite samples with x = 0 and 0.025 have single-phase cubic spinel structure. It is found that when the doping amount is 0.05 or >0.05, the secondary-phase Bi₂O₃ peak appears. The average crystallite size of the sample was calculated by Debye–Scheller formula. It was found that the average grain size of the sample was affected by the doping concentration. With the increase in Bi³⁺ ion content, the average crystallite size increases from 8.3797 nm to 8.3940 nm. The structure of Bi³⁺ ion-doped Ni–Mg–Co ferrite was further characterized by FT-IR. There are two absorption bands ν₁ and ν₂ at 584 and 397 cm⁻¹, which further prove the spinel structure. The morphology of the sample particles was observed by SEM, and the distribution of the particle size was calculated. The chemical components of powder samples were analyzed by EDS. Through VSM analysis, the Bi³⁺ ion-doped Ni–Mg–Co ferrite has the characteristics of ferromagnetism. With the increase in Bi³⁺ ion content, the residual and saturation magnetization decreased; the magnetic stability is also reduced. The results show that the magnetic properties of Bi³⁺ion-doped Ni–Mg–Co ferrite are decreased.

本文采用高纯硝酸盐和柠檬酸实验材料，通过溶胶-凝胶自动燃烧法制备了Bi ³⁺离子掺杂的Ni-Mg-Co铁氧体纳米磁性材料。还研究了Bi ³⁺离子含量对纳米铁氧体晶格结构和磁性的影响。XRD衍射图分析表明，x  = 0和0.025的Ni-Mg-Co铁氧体样品具有单相立方尖晶石结构。发现当掺杂量为0.05或> 0.05时，第二相Bi ₂ O ₃出现峰值。样品的平均微晶尺寸通过Debye–Scheller公式计算。发现样品的平均晶粒尺寸受掺杂浓度影响。随着Bi ³⁺离子含量的增加，平均晶粒尺寸从8.3797 nm增加到8.3940 nm。FT-IR进一步表征了Bi ³⁺离子掺杂的Ni–Mg–Co铁氧体的结构。有两个吸收带ν ₁和ν ₂在584和397厘米^-1，进一步证明了尖晶石的结构。通过SEM观察样品颗粒的形态，并计算粒径的分布。用EDS分析粉末样品的化学成分。通过VSM分析，Bi ³⁺离子掺杂的Ni-Mg-Co铁氧体具有铁磁性的特征。随着Bi ³⁺离子含量的增加，剩余磁化强度和饱和磁化强度均降低。磁稳定性也降低。结果表明，Bi ³⁺离子掺杂的Ni–Mg–Co铁氧体的磁性能下降。