Mn和Fe掺杂对尖晶石氧化物Co2MnO4结构和磁性的影响

以金属盐及柠檬酸为原料, 采用溶胶-凝胶法制备了尖晶石氧化物Co_2-xMn_1+xO₄和Co_2-xFe_xMnO₄系列, 通过XRD、FT-IR及PPMS等手段研究了Co₂MnO₄及系列掺杂样品的成相、结构、磁性等特征。结果表明, Co_2-xMn_1+xO₄系列在x<0.6时, 呈单相立方结构, 晶格常数和磁性随着Mn掺杂量的增加而增大, x≥0.6时逐渐向四方结构转化, 磁性下降, 并呈现磁化强度不易饱和的特征; Co_2-xFe_xMnO₄系列样品在x<1.75成分范围内均可保持立方结构, 且晶格常数和磁性都随着x增大而提高。这些变化主要是由于掺杂原子尺度及磁矩均大于原有元素, 掺杂后样品内部的磁性相互作用有所增强。

Structure and Magnetic Property of Fe and Mn Doped Spinel Co2MnO4

Spinel solid solution Co_2-xMn_1+xO₄ and Co_2-xFe_xMnO₄ were synthesized by Sol-Gel method using metal nitrates and citric acid as the starting materials. Crystalline phases, structure and magnetic properties of the Co₂MnO₄ doped with different concentrations of Fe and Mn were investigated by XRD、FT-IR and PPMS, respectively. Results show that Co_2-xMn_1+xO₄ series are single-phase cubic spinel structure at x<0.6, the lattice parameter as well as the saturation magnetization are found to be increasing with the Mn content increasing. Co_2-xMn_1+xO₄ series transform to tetragonal structure gradually at x≥0.6, which result in the decline of magnetic properties and difficulty of reaching saturation. Co_2-xFe_xMnO₄ samples have cubic spinel structure at x<1.75, the lattice parameter and magnetic increase with the increase of Fe-substitution. When the Fe content increases to 1.75, Fe₂O₃ phase is formed in the sample. The changes of performance are mainly due to the larger atom radius of the doping atoms (Fe or Mn) as compared to that of Co. And magnetic moment is another important factor to the performance change. The first-principles calculation results show that the magnetic moments of Fe and Mn are larger than that of Co. As a result, the interatomic magnetic interaction is enhanced by doping.