Effect of rare earth doping on magnetic and dielectric properties of NiZnMn ferrites

Abstract

In present work, RE0.01Ni0.3Zn0.4Mn0.3Fe2O4 (RE=Fe, La, Nd, Sm, Gd, Dy, Yb) ferrites with strictly controlled main composition were prepared. X-ray diffraction analysis shows that the lattice constant decreases with the increase of atomic number of rare earth. The infrared spectra demonstrate the changes of tetrahedral and octahedral bonds. The saturation magnetization is about 74 emu/g and initial permeability is about 120 for undoped ferrite. They decrease slightly after rare earth doping, but the impact of different rare earth on Ms is same. The Curie temperature of almost all samples is 262 ℃. Zero field cooling-field cooling curves demonstrate the existence of spin glass state or superparamagnetism at high temperature. Sm, Gd and Dy doped ferrites have special dielectric properties with more relaxation processes. Appropriate rare earth doping greatly improve the cut-off frequency, dielectric constant for MHz device materials and dielectric loss for GHz electromagnetic wave absorption materials.