Magnetic properties of nanosized Mg_(0.5)Mn_(0.5)(RE)_(0.1)Fe_(1.9)O_4 ferrites synthesized by glycol-thermal method

摘要

Nanosized Mg_(0.5)Mn_(0.5)(RE)_(0.1)Fe_(1.9)O_4 ferrites, where RE are the rare earth elements, have been synthesized by the glycol-thermal method from pure metal chlorides. The as-prepared samples in the form of powders were characterized by X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM). The XRD and HRTEM data show formation of the single-phase cubic spinel structure. The grain sizes are found in the range 9-15 nm. Magnetic properties of the as-prepared samples were obtained at room temperature by ~(57)Fe-M6ssbauer spectroscopy and by a vibrating sample magnetometer. The distributions of Fe~(3+) ions were also deduced from Mossbauer measurements. The variations of grain size, lattice parameter, coercive field, magnetizations are presented as a function of the number of (RE)~(3+) 4/electrons. Our results show the evidence for superparamagnetic behavior of the rare earth substituted compounds. The highest grain size and magnetizations are obtained for the Gd substituted sample. We also find strong correlation of the saturation magnetizations, grain sizes and microstrains with the de Gennes factor.