Ho3+掺杂对六角YMn0.8Fe0.2O3微结构和磁性质的调控

本文利用高温固相反应法合成了六角Y_1-xHo_xMn_0.8Fe_0.2O₃多晶样品,研究Ho³⁺掺杂对YMn_0.8Fe_0.2O₃微结构以及磁性质的影响。X射线衍射和拉曼测量结果显示所有样品均为单相六角结构,当Ho³⁺掺杂浓度低于0.15时,晶格常数a、c,晶胞体积及Mn—O键长均随着掺杂浓度的增加而减小。A位稀土原子位移差以及拉曼声子模式的变化表明随着Ho³⁺掺杂比例增加,A位稀土原子相对于平面的偏移减小,MnO₅双锥体倾斜角减小,B位Mn³⁺的三聚作用被削弱,Mn³⁺—O^2-—Mn³⁺间超交换作用减弱,反铁磁(AFM)序被抑制,反铁磁转变温度下降。磁性测量显示低温下Y_0.9Ho_0.1Mn_0.8Fe_0.2O₃的磁化强度显著增强,弱铁磁(WFM)序增加,归因于Ho³⁺加入后系统磁阻挫行为的降低及Ho³⁺—O^2-—Mn³⁺间自旋交换作用产生的铁磁序。这为进一步探索室温多铁性材料提供了思路。

Regulation of Microstructure and Magnetic Properties of Hexagonal YMn0.8Fe0.2O3 by Doping Ho3+

Hexagonal Y_1-xHo_xMn_0.8Fe_0.2O₃ polycrystalline samples were synthesized by high-temperature solid-state reaction method. The effects of Ho³⁺ doping on microstructure and magnetic properties of YMn_0.8Fe_0.2O₃ were investigated in this paper. X-ray diffraction (XRD) and Raman spectra (RS) show that all samples are of single-phase hexagonal structure without another impurity phase. When the doping concentration (x) of Ho³⁺ is lower than 0.15, the lattice constants, unit cell volume and bond length between the Mn—O of the samples decrease with x increasing. The decrease of the lattice constants may be related to the interaction between the Mn³⁺/Fe³⁺ 3d orbital and the Ho³⁺ 4f orbital, resulting in lattice distortion and electron loss. The displacements of the rare-earth atoms at the A-site relative to the plane and the inclination of the MnO₅ bipyramids are suppressed with increasing doping concentration, which is demonstrated by the shift deviations of the rare-earth atoms and the variations of the Raman phonon modes. At the same time, the trimerization of Mn³⁺ at the B-site is weakened. The magnetic properties of the samples were measured using the superconductor quantum interference device (SQUID). Results show that the antiferromagnetic (AFM) order decreases upon Ho³⁺ doping, consistent with the reduced superexchange interaction between Mn³⁺—O^2-—Mn³⁺. The AFM transition temperature T_N decreases. Besides, the magnetization of the samples and the weak ferromagnetic (WFM) order at low temperature are significantly enhanced, which is attributed to the suppressed magnetic resistance behavior of the system and the ferromagnetic order generated by the spin exchange interaction between Ho³⁺—O^2-—Mn³⁺. These provide an idea for us to further explore room temperature multiferroic materials.