Magnetic properties of Zn2+ substituted ultrafine Co-ferrite grown by a sol-gel method

Abstract

Ultrafine Co1−xZnxFe2O4 (0⩽x⩽1.0) particles are fabricated by a sol-gel method. The magnetic and structural properties of powders were investigated with x-ray diffraction, vibrating samples magnetometer and Mössbauer spectroscopy. The lattice parameter (a0) increases linearly with increasing Zn concentration (x) and follows Vegard’s law approximately. Co0.9Zn0.1Fe2O4 powders that were annealed at and above 673 K have only a single phase spinel structure and behave ferrimagnetically. Powders annealed at 523 K and 573 K have a typical spinel structure and are simultaneously paramagnetic and ferrimagnetic in nature. The magnetic behavior of Co0.9Zn0.1Fe2O4 powders annealed at and above 573 K shows that an increase of the annealing temperature yields a decrease of the coercivity and an increase of the saturation magnetization. The maximum coercivity and the saturation magnetization of Co0.9Zn0.1Fe2O4 ferrite powders are 1328 Oe and 81.1 emu/g, respectively. Mössbauer spectra of Co–Zn ferrite have been taken at various temperatures from 20 to 800 K. The isomer shifts indicate that the iron ions were ferric at the tetrahedral [A] and the octahedral [B]. The Néel temperature of Co0.9Zn0.1Fe2O4 was determined to be TN=790 K and It is found that Debye temperature for the A and B sites of the sample annealed at 1123 K is found to be ΘA=756±5 K and ΘB=199±5 K, respectively. The Néel temperature dramatically decreased with increasing x from about TN=870 K for x=0.0 to TN=35 K for x=1.0.