采用溶胶--凝胶法制备了Co1-xNixFe2O4/SiO2(0 ≤x ≤1.0)纳米复合材料. 利用XRD, TEM, 振动样品磁强计(VSM)和Mossbauer谱测试了900℃热处理样
品的结构、晶粒尺寸和磁性. 结果表明, 样品中Co1-xNixFe2O4铁氧体的平均晶粒尺寸在15---20 nm之间, Ni2+的掺杂引起CoFe2O4晶胞体积减小. VSM结果表明, 随Ni2+含量的增加, 样品的比饱和磁化强度和矫顽力变小. Mossbauer谱表明, 室温下各样品均处于磁有序状态, 样品的内磁场随Ni2+含量的增加而变小.
Nanocomposites Co1-xNixFe2O4/SiO2 were prepared by sol–gel method using tetraethyl orthosilicate and nitrates, in which SiO2 is used to restrict the growth of ferrite crystalline and remove the agglomeration. XRD and TEM are used to characterize structures and morphologies. The composites sintered at 900 ℃consist of spinel phase with size ranging from 15 to 20 nm and amorphous SiO2. The doping of Ni2+ reduces the volume of unit cell of the spinel phase. The magnetic properties of the Co1-xNixFe2O4/SiO2 nanocomposites were measured by vibrating sample magnetometer and Mossbauer spectroscopy. The results indicate that the saturation magnetization decreases from 41.8 A·m2/kg to 23.0 A·m2/kg with increasing Ni2+ content. At the same time the coercivity decreases from 104.2 kA/m to 5.4 kA/m, which may originate from the variation of anisotropy induced by Co2+ ions in octahedral sites. All the samples are magnetic order state, the hyperfine magnetic field of the nanocomposites decreases with increasing Ni2+ content.
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