Study of combined effect of partial Bi doping and particle size reduction on magnetism of La_0.7Sr_0.3MnO₃

La_0.7Sr_0.3MnO₃ has been subjected to simultaneous partial bismuth substitution and particle size reduction to understand the mechanism controlling the magnetic properties. Nanosized samples of 10% Bi doped La_0.7Sr_0.3MnO₃ samples were prepared by high energy planetary ball milling. Compared to pristine La_0.7Sr_0.3MnO₃, 10% Bi doping results in the reduction of saturated magnetic moment and Curie temperature. Using the ‘top-down approach’ through high energy planetary ball milling, particle size reduces from 250 nm for bulk to 26 nm for 48 h ball milled sample. Correspondingly, the magnetic properties show the direct influence of size reduction, as the observed magnetic moment shows drastic decrease as particle size reduces. It is interesting to note that 10% Bi doping in La_0.7Sr_0.3MnO₃ plays important role in controlling the size with respect to milling time. In the present work, we discuss the magnetic properties of nanostructured La_0.6Bi_0.1Sr_0.3MnO₃ samples. The observed magnetization behaviour can be described using the core-shell model for nanoparticles.