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Nanoparticles Cr x Al 0.5-x CoFe 1.5 O 4 (x=0.1, 0.25 and 0.4) spinel ferrites were synthesized by coprecipitation technique, aiming to study the relationship between cation distribution of the substitution of chromium and aluminum ions on the structure, morphology, magnetic properties, permeability, Curie temperature and AC loss. X-ray diffraction (XRD) analysis used with Rietveld refinement revealed nanocrystalline single-phase of the spinel ferrites. The calculated average crystallite size is between 40 and 45 nm. The obtained results show, that both lattice constant and total porosity increased by increasing Cr 3+ concentration. It was found that Al 3+ occupied tetrahedral (A) and octahedral (B) sites whereas, Cr 3+ preferred to occupy only octahedral (B) sites. The magnetization M s, coercivity H c and the magneto-crystalline constant k 1 decreased with increasing Cr 3+ content. Likewise, Curie temperature T C decreased from 670 K to 585 K with increasing Cr 3+ concentration. Magnetic loss has further been observed and increased with increasing Cr 3+ concentration in all investigated samples.

Structural, optical, magnetic, and electrical properties of zinc oxide (henceforth, ZO) and iron doped zinc oxide (henceforth, ZOFe) films deposited by sputtering technique are described by means of Rutherford backscattering spectrometry, grazing incidence X-ray diffraction, scanning electron microscope (SEM), UV–Vis spectrometer, vibrating sample magnetometer, and room temperature electrical conductivity, respectively. GIXRD analysis revealed that the films were polycrystalline with a hexagonal phase, and all films had a preferred (002) c-axis orientation. The lattice parameters a and c of the wurtzite structure were calculated for all films. The a parameter remains almost the same (around 3 Å), while c parameter varies slightly with increasing Fe content from 5.18 to 5.31 Å throughout the co-deposition process. The optical gap for undoped and doped ZO was obtained from different numerical methods based on the experimental data and it was increased with the increment of the concentration of Fe dopant from 3.26 eV to 3.35 eV. The highest magnetization (4.26 × 10−4 emu/g) and lowest resistivity (4.6 × 107 Ω·cm) values of the ZO films were found to be at an Fe content of 5% at. %. An explanation for the dependence of the optical, magnetic, and electrical properties of the samples on the Fe concentrations is also given. The enhanced magnetic properties such as saturated magnetization and coercivity with optical properties reveal that Fe doped ZO thin films are suitable for magneto-optoelectronic (optoelectronic and spintronics) device applications.

This study is an attempt to produce gadolinium-doped iron oxide nanoparticles for the purpose of utilization in magnetic fluid hyperthermia (MFH). Six gadolinium-doped iron oxide samples with varying gadolinium contents ( were prepared using the hydrothermal method and high vapor pressure to incorporate gadolinium ions in the iron oxide structure. The samples were indexed as , with varying from 0.0 to 0.1. The results reveal that gadolinium ions have a low solubility limit in the iron oxide lattice (x = 0.04). The addition of gadolinium caused distortion in the produced maghemite phase and formation of other phases. Based on X-ray diffraction (XRD) analysis and photoelectron spectroscopy (XPS), it was observed that gadolinium mostly crystalized as gadolinium hydroxide, for gadolinium concentrations above the solubility limit. The measured magnetization values are consistent with the formed phases. The saturation magnetization values for all gadolinium-doped samples are lower than the undoped sample. The specific absorption rate (SAR) for the pure iron oxide samples was measured. Sample GdIO/0.04, pure iron oxide doped with gadolinium, showed the highest potential to produce heat at a frequency of 198 kHz. Therefore, the sample is considered to hold great promise as an MFH agent.