Structural, AC, and DC magnetic properties of Zn 1 x Co x Fe 2 O 4

Structural, AC and DC magnetic properties of polycrystalline Zn1� xCoxFe2O4 (x ¼ 0.2, 0.4) samples sintered at various temperatures (1100–13001C), and various dwell times (0.2–15 h) have been investigated thoroughly. The bulk density of the Zn0.60Co0.40Fe2O4 samples increases as the sintering temperature (Ts) increases from 1100 to 12501C, and above 12501C the bulk density decreases slightly. The Zn0.80Co0.20Fe2O4 samples show similar behavior of changes to that of Zn0.60Co0.40Fe2O4 samples except that the bulk density is found to be highest at 12001C. The DC magnetization as a function of temperature curves show that the Zn0.60Co0.40Fe2O4 sample is ferrimagnetic at room temperature while the Zn0.80Co0.20Fe2O4 sample is paramagnetic at room temperature. The Tc of Zn0.80Co0.20Fe2O4 sample is found to be 170 K from DC magnetization measurement. Separate measurement (AC magnetization), initial permeability as a function of temperature shows that the Tc of the Zn0.60Co0.40Fe2O4 sample is 353 K. Slight variation of Tc is observed depending on sintering condition. The initial permeability for the Zn0.60Co0.40Fe2O4 composition sintered at 12501C is found to be maximum. r 2007 Elsevier Ltd. All rights reserved. PACS: 75.50.G; 75.50.Gg; 61.72.M