Magnetic behaviors of Co1−xZnxFe2O4 nano-particles

Abstract

A series of Co1−xZnxFe2O4 particulate nano-ferrites with x = 0, 0.2, 0.4, 0.5, 0.6, 0.7, and 0.8, fabricated by the co-precipitation method, have been investigated. The lattice parameter is found to increase and particle size decreases with increasing x. Mössbauer spectroscopy at room temperature exhibits ferromagnetic hyperfine splitting sextet peaks with a doublet peak overlapping at its center as Zn contents x < 0.6, and only a single doublet as x ≥ 0.7. The fitting results of Mössbauer spectra reveal the occupation rule of nonmagnetic Zn2+ ions and superparamagnetic behavior. At room temperature, the superparamagnetic excitation plays an important role in the magnetic properties. The fitted hyperfine magnetic field of the octahedral and tetrahedral sublattices decreases with increasing Zn content. The saturation magnetization and coercivity monotonously reduce to a small value. However, at low temperature of 5 K, the saturation magnetization (Ms) fully reflects the occupation of Zn ions. Zn substitutions that occupied first the tetrahedral sites cause the increase of magnetization when Zn content is below 0.4, while when Zn content is above 0.4, Zn substitutions occupied both the tetrahedral sites and the octahedral site, which leads to the decrease of magnetization.