Microwave non-resonant absorption in fine cobalt ferrite particles

Cobalt ferrite particles of average crystallite size of 11 nm were obtained by a sol-gel process at 400 degrees C. The powders were annealed at temperatures of 500, 600, 700 and 800 degrees C in air. Derivative microwave power absorption (dP/dH) measurements were carried out as a function of magnetic field (H-DC) at X band (9.4 GHz), in the field range -80-796 kA/m for all annealed temperatures. In order to compare the response of saturation magnetization measurements with high frequency measurements, we calculated the areas inside both the magnetization (A(M)) and the absorption hysteresis loops (A(LFS)). The dependence of these areas as a function of crystallite size is remarkably similar in both experiments. (C) 2007 Elsevier B.V. All rights reserved.