| Summary: | 碩士 === 中國文化大學 === 化學工程與材料工程學系奈米材料碩士班 === 104 === Mn0.1Mg0.9CrxFe2-xO4 (x=0, 0.1, 0.2, 0.3, and 0.5) ceramics have been synthesized with the solid state method to study the frequency and temperature dependent of the Neel relaxation behavior in these compounds. All un-dopant and Cr-doping samples were formed spinel cubic structure, which has been checked by powder X-ray diffraction. The OM images in the Mg-Mn ferrite samples are shown that the grain size is increasing with sintering temperature increasing, but decreasing with Chromium concentration increasing. The grain size has been counted by the intercept technique through the OM images.
Room temperature AC magnetic susceptibility measurement is showed that all samples obey Neel magnetic relaxation behavior. The real part of magnetic susceptibility is gradually decreasing around the magnetic resonance frequency and the imaginary part of magnetic susceptibility is appeared a broad magnetic resonance peak due to magnetic loss.
Low temperatures AC magnetic susceptibility has been measured vary temperature, which was fitted the Debye relaxations model to calculate the resonance frequency (f0), and the magnetic anisotropy energy can be computed by the lnf0 versus reciprocal temperature plot. The maximum magnetic anisotropy energy of 1300oC sintering temperature samples is x=0.3, but the anisotropy energy is gradually decreasing with Cr doping level x increasing except x=0.2 and 0.3 samples.
In this work, we reported that bulk or powder samples can measure the magnetic anisotropy energy by temperature dependent AC susceptibility method to compares with Magneto Optical Kerr Effect measurement, which is more convenient way to measure the magnetic anisotropy energy and doesn’t limit to thin films.
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