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

• Studies on La0.67Sr0.33−xKxMnO3(x = 0–0.15) nanoparticles (NPs) have been made.
• Ms and Tc increase because of the incorporation of K in La/Sr−site upto x = 0.1.
• These NPs show nearly superparamagnetic behaviour at room temperature.
• A good fit of the M-H data with Langevin function is obtained.
• Such superparamagnetic NPs can have potential biomedical applications.

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 R3¯C space group for all samples. From the results of transmission electron microscopy it is evident that the samples, sintered at 800 and 1100 °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 (Ms) 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 Ms and TC decrease. The studied NPs can have wide applications in the field of targeted drug delivery and hyperthermia treatments.