Synthesis of cobalt ferrite nanocrystallites by the forced hydrolysis method and investigation of their magnetic properties

Cobalt ferrite powder has been synthesized by the forced hydrolysis method in 1,2-propanediol. The particles, having a cubic spinel structure, are nanocrystallites with a mean diameter of 4 nm with almost equiaxial shapes and a narrow size distribution. These particles are superparamagnetic at room temperature and ferrimagnetic at temperatures below the blocking temperature of about 180 K. A remarkable shift of the blocking temperature with frequency was observed in the AC susceptibility measurements. The calculated value of anisotropy constant at 0 K, K-A (0) = 5.36 x 10(7) erg/cm(3), is higher than that in the bulk material. The saturation magnetization and the coercivity measured at 5 K are 75 emu/g and 10.3 kOe, respectively. (C) 2002 Elsevier Science B.V. All rights reserved.