Structural, magnetic, dielectric and optical properties of Sr1-xMnxFe2O4 nanoparticles fabricated by sol-gel method

In this paper, strontium-manganese spinel ferrite nanoparticles (Sr1-xMnxFe2O4) with x = 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, and 0.7 were synthesized using the sol-gel method. In order to characterize the strontium-manganese spinel ferrite nanoparticles, X-ray diffraction pattern, Fourier transform infrared spectroscopy, Field emission scanning electron microscope, Vibrating sample magnetometer, LCR meter, and Ultraviolet-visible (UV-vis) spectrometer were used. The X-ray diffraction pattern analysis showed that a single-phase spinel ferrite structure had been formed in the sample with x = 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, and 0.7 at a temperature of 700 °C for 4 h. FT-IR analysis results of the samples showed that the tetrahedral and octahedral sites, which are among the important characteristics of spinel ferrites, were formed. Also, the study of Field emission scanning electron microscope images showed that strontium-manganese spinel ferrite particles are homogeneous but since the samples have a magnetic property, the particles of the samples are aggregated. The hysteresis loops results show that the saturation magnetization of the samples increases up to x ≤ 0.6, and for the samples with doping more than x = 0.6, it decreases. These changes in the saturation magnetization of the samples are due to the distribution of the magnetic moments in the tetrahedral and octahedral sites. The results of ultraviolet-light spectroscopy studies show that with the increase of Mn, the optical gap of strontium-manganese spinel ferrite nanoparticles decreases. Also, the dielectric measurements of the samples showed that the dielectric constant and the dielectric loss increased as a result of increasing Mn ions in the samples. The dielectric constant and the dielectric loss of the samples also decrease due to increasing frequency. These changes indicate normal behavior in the ferrites, which can be justified by the Maxwell-Wegener model and the Koop's theory.