Effect of heat treatment on Jahn–Teller distortion and magnetization in Cu ferrite nanoparticles

Cu ferrite (CuFe2O4) nanoparticles were prepared by a wet chemical method. Heat treatment was performed using an electric furnace in an air atmosphere at temperatures between 973 and 1223 K. Some samples were quenched after annealing; three different quenching methods were adopted. The particle diameters, as estimated from X-ray diffraction (XRD) patterns, ranged from 6 to 37 nm. Tetragonal Cu ferrite with Jahn–Teller distortion or cubic Cu ferrite without Jahn–Teller distortion was obtained, depending on the heat treatment method used. X-ray absorption fine structure (XAFS) spectra supported the observed structural differences. Magnetization measurements were performed on each sample at a DC field of ±50 kOe. The saturation magnetization of cubic Cu ferrite was greater than that of the distorted cubic structure.