Studies on characteristic properties of superparamagnetic La0.67Sr0.33-xKxMnO3 nanoparticles

This paper reports the study of the structural, morphological and magnetic properties of La0.67Sr0.33-xKXMnO3 (x=0-0.15) nanoparticles (NPs), prepared by sol gel method. The Rietveld analysis of the X ray diffraction data was carried out for crystal structure refinement confirming the rhombohedral structure with RC space group for all samples. From the results of transmission electron microscopy it is evident that the samples, sintered at 800 and 1100 degrees C, have grain size in the range 20-35 and 30-50 nm respectively. While studying the magnetization as a function of applied magnetic field, it is observed that most of these NPs show nearly superparamagnetic behaviour at room temperature and a good fit of these data with Langevin function is obtained. The temperature varying field-cooled magnetization data show that the saturation magnetization (M-s) as well as Curie temperature (T-C) increases because of the incorporation of K in La/Sr-site upto x = 0.1; above this doping both M-s and T-C decrease. The studied NPs can have wide applications in the field of targeted drug delivery and hyperthermia treatments. (C) 2015 Elsevier B.V. All rights reserved.