Structural, magnetic and magnetocaloric properties of Nanostructured La_0.5Bi_0.2Sr_0.3MnO₃ perovskites

Nanostructured La_0.5Bi_0.2Sr_0.3MnO₃ samples were synthesized by high energy planetary ball milling to study the effect of milling time on crystal structure, particle size and magnetic properties. Addition of 20% Bi at La site in La_0.7Sr_0.3MnO₃ matrix suppresses ferromagnetism significantly. On increasing the milling time from bulk (0 h) to 48 h the particle size reduces from 173 nm to 22 nm. The ferromagnetic ordering temperature decrease from 312 K to 302 K, with drastic decrease in the magnitude of magnetization as milling times changes to 48 h. Based on phenomenological model, the magnetocaloric properties have been studied. The diminished values in change of magnetic entropy with increase of milling time may be described by the evolution of disordered magnetic states on the surface of nanoparticles. It is interesting to notice that 20% Bi for La site plays an important role in controlling the particle size and modifying the magnetic properties.