Investigation of Physical Properties for Nano structured Magnetic Materials Treated by Irradiation

Nanoparticle ferrite with the chemical formula Mg_1-xZn_xFe₂O₄ (where x=0.0, 0.1, 0.2, 0.3, 0.4 and 0.6) have been prepared by the sol-gel technique. The composition and purity of ferrite are hardly affected their properties. Therefore, the elemental concentration of these samples was measured by the X-ray fluorescence and thermal neutron activation analysis techniques to check the real composition of the prepared samples. The results of both methods were compared with each other and with the molecular ratios of the as-prepared samples. No existing elemental impurity was detected. The samples were characterized by X-ray diffraction (XRD) and Infrared analysis (IR). Single-phase structure of these ferrites was confirmed using (XRD). All samples showed two absorption bands in the IR spectra,ν_t and ,ν_o, in the absorption range 550 and 400 cm^-1, respectively. Transmission Electron Microscope (T E M) showed that the particle size of the samples lies in the range of (5.7–10.6 nm). The hysteresis studies revealed superparamagnetic behavior at room temperature for all samples. The dead layer thickness (t) was calculated and its effect on the magnetization and magnetic losses was discussed. The Specific Absorption Rate (S A R) in an alternating magnetic field operating at a frequency 198 khz for these ferrites has been studied. It was found that the sample with x = 0.2 has the highest value of S A R although it does not has the highest value of saturation magnetization Sample with the chemical formula Mg_0.8Zn_0.2Fe₂O₄ i.e. x = 0.2 was annealed at temperatures of 400, 600 and 800 degree C for 4 hours. No extra lines were observed in the XRD spectra for all annealed samples. The sample Mg_0.8Zn_0.2Fe₂O₄ ferrites showed superparamagnetic phase as that the as-prepared and annealed samples at 400 and at 600 degree C, respectively. On the other hand, the annealed sample at 800 degree C showed hysteresis behavior with H_c = 7.89 mt and M_r = 5.86 emu/g. On annealing, up to 600 degree C, S A R values decreased and above it, the S A R values increased. Moreover, the sample with x = 0.2 has been doped by Gd₃₊ according to the chemical formula Mg_0.8Zn_0.2Fe_2-yGd_yO₄ (where y = 0.025, 0.05, 0.075, and 0.1) and these samples were also prepared by sol-gel technique. XRD for all investigated samples confirmed single spinel phase structure. T E M analysis showed that the particle size of the samples lies in the range of (12–32 nm). Mg_0.8Zn_0.2Fe_2-yGd_yO₄ ferrite nanoparticles displayed superparamagnetic phase. The saturation magnetizations for the doped samples with Gd³⁺ ions are lower than that of undoped one and decreased with the Gd³⁺contents.The S A R values also decreased after doping