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

Hexagonal Y_{1 - x} Ho_x Mn_0.8 Fe_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_0.8 Fe_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 TN 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. [ABSTRACT FROM AUTHOR]