The Effect of Annealing Temperature on the Magnetic Properties of Mn x Co1-x Fe2O4 Ferrites Nanoparticles

Mn (x) Co1-x Fe2O4 ferrites compounds (0a parts per thousand currency signxa parts per thousand currency sign0.6) have been synthesized by a glycol-thermal method from high-purity metals chlorides. Single phase spinel structure of the nanoparticles has been confirmed by X-ray diffraction (XRD) and transmission electron microscopy (TEM) measurements. The diameters of the as-prepared powders were estimated from XRD and TEM and were found to be in the range: 7 to 13 nm. Room temperature magnetizations were obtained using a vibrating sample magnetometer (VSM) on the as-prepared samples and on samples annealed at 500 and 700 A degrees C. The variation of coercive fields, saturation and remnant magnetizations as a function of composition (x) and grain size have been investigated. Co-57 Mossbauer spectra for as-prepared samples were also measured at different temperatures (27, 100, and 200 A degrees C). Significant changes in magnetization properties and Mossbauer parameters are observed across the composition range studied. The variation of coercive fields and saturation magnetizations appear to critically depend on the particle sizes as the compounds evolve from single domain to multidomain structure.