Magnetic Studies Of Nonmagnetic Ions Substituted Cobalt And Magnesium Ferrites

Ferrite is a metal oxide of ferromagnetism, it generally can be divided into permanent magnetic ferrite, soft magnetic ferrite and gyromagnetic ferrite, etc. In the research field of permanent magnet ferrite, Cobalt ferrite is a hard magnetic material, it has moderate saturation magnetization, high coercivity, high anisotropy constant and high Curie temperature, Moreover cobalt ferrite exhibit high electromagnetic performance, large magneto-optic effect, excellent chemical stability and mechlanical hardness. Cobalt ferrite of the well known hard magnetic materials has been widely used as high-density recording medium. Furthermore cobalt ferrite is one of the most promising candidates for microwave devices, magneto-optics devices, sensors. In the research field of soft magnetic ferrite, magnesium ferrite is a soft magnetic n-type semiconducting material, which is used in gas sensors, transformers, ferrofluids, fuel cells and magnet core of coils. At present, the investigate variation structural and magnetic properties of ferrite powders by replacement ions is an important research direction. In this paper, we choose the nonmagnetic Gd3+and Mg2+ions to substitut cobalt ferrite, study performance of Zn2+ions substituted magnesium ferrite simultaneously. The morphology, structural and magnetic properties of ferrite powders were investigated with x-ray diffraction (XRD), scanning electron microscopy (SEM), Mossbauer spectroscopy and superconducting quantum interference device (SQUID).In this paper, all ferrite powders have been prepared by a sol-gel auto-combustion method. Under appropriate PH value, inorganic compounds or metal organic solvents and complexing agent through hydrolysis and complexation reaction form sol, aging become wet gel, drying obtain dry gel, get puffy dendritic ashes after auto-combustion, the formation of dense ferrite powder materials after grinding and high temperature sintering. Sol-gel auto-combustion method was simple and economic way to prepare nano scale ferrite powder. It has the advantages of using inexpensive precursors, low external energy consumption and resulting nano sized, homogenous highly reactive powder.The main results of this paper are given as follows: 1. CoGdxFe2xO4ferrite powder after at800℃sintering. XRD results indicate that the production is a single cubic phase. SEM shows that the ferrite powers are nano-particles and the average grain size decrease with the substitution of rare earth ions. Room temperature Mossbauer spectra of CoRExFe2xO4are two normal Zeeman-split sextets. The saturation magnetization decreases and the coercivity increase by the RE ions.2. Co1-xMgxFe2O4ferrite powder after at800℃sintering. XRD results indicate that the production is a single cubic phase. the average grain size increase with increasing Mg contente obtained by SEM. It was confirmed ferrimagnetic behaviour of all sample by Mossbauer spectra. The saturation magnetization and the coercivity all decreases with increasing Mg content.3. Synthetic Mgi-xZnxFe2O4ferrite powder after at800℃sintering, XRD show that only the specimens with x=0.5and0.7exhibit single-phase spinel structure, and more content of Zn in specimens is favorable for the synthesis of pure Mg-Zn ferrites. And the ferrite powers are nano-particles from the SEM. It was confirmed that transition from ferrimagnetic to superparamagnetic behaviour depend on increase in zinc concentration by Mossbauer spectra. With increasing Zn content, the saturation magnetization increases and the coercivity decreases.4. the sample annealed at different temperature, the XRD diffraction peaks of the sample without calcining is sharpness. So we prepared cobalt ferrite powders by a sol-gel auto-combustion method, have a good crystallinity. Mossbauer spectra of the ferrite annealed at different temperatures show that the calcining temperature influence the magnetic property.At last, we summarize the work in the paper and discussthe prospects of the study of nonmagnetic ions substituted ferrites.