Magnetic behavior of nanocrystalline MnCo2O4 spinels

A series of powders with different particle sizes of the,spinel MnCo2O4 was synthesized by the Pechini method. The resulting precursor was calcined between 400 and 900 degrees C and characterized by thermogravinietric analyses (TGA), X-ray diffraction (XRD), scanning electron microscopy (SEM) and magnetization measurements. TGA analysis showed a loss of mass in the region from 200 to 650 degrees C and stability after this. XRD patterns showed an increase of the crystallite size with calcination temperature. Magnetization measurements oil the sample calcined at 900 degrees C showed an unusual behavior of the hysteresis curve and irreversibility of the magnetization with field cooled (FC) and zero field cooled (ZFC) procedures. An evolution of this behavior was observed with increasing crystallite size. (c) 2005 Elsevier B.V. All rights reserved.