Structural, Magnetic, and Electrical Properties of REFe۰.۷Cr۰.۳O۳ (RE= La, Pr, Nd, Sm, and Gd) Compounds

In this research, crystal information, magnetic, and electrical properties of REFe۰.۷Cr۰.۳O۳ nanoparticles were investigated via X-ray diffraction data, field-emission scanning electron microscopy images, magnetic hysteresis loops and dielectric measurements, respectively. All samples were synthesized by the sol-gel method. Results related to powder X-ray diffraction indicate that all samples are single-phase and crystallize in orthorhombic symmetry with Pbnm space group. By varying the rare earth (RE) ions from La to Gd, the unit cell volume decreases due to the reduction in the RE ionic radius. All samples display a weak ferromagnetic behavior with low remanent magnetization and coercivity field. The Néel transition temperature of the studied samples was determined by the temperature dependence of their magnetization. Results reveal that the Néel temperature values decrease from ۵۸۳ K to ۴۹۸ K with decreasing ionic radius of the RE ions. The frequency dependence of the dielectric constant in all samples follows the Maxwell-Wagner polarization model. The high dielectric constant at low frequencies emphasized the polarization mechanism associated with space charges. The LaFe۰.۷Cr۰.۳O۳ sample exhibits a colossal dielectric constant in the low-frequency range at room temperature, which can be played play a significant role in miniaturizing electronic components and fabricating high-capacitance dielectric capacitors. The frequency dependence of ac conductivity indicates a small polaron hopping mechanism. To clarify the transport mechanism for of the REFe۰.۷Cr۰.۳O۳ samples, the variations of direct electrical conductivity versus temperature were studied, which revealed a semiconducting nature.

کلیدواژه ها:

Orthoferrites ، Sol-Gel Method ، Magnetization ، Néel temperature ، Dielectric constant ، conductivity