Effect of milling on structure and magnetism of nanocrystalline La_0.7-xBi_xSr_0.3MnO₃ (x = 0.35, 0.40) manganites

Polycrystalline bulk samples of La_0.7-x Bi_xSr_0.3MnO₃ (x = 0.35 and 0.40) manganites have been subjected to high energy planetary ball milling to prepare nanoparticles by using the top-down approach. A significant drop in the particle size has been observed with an increase in milling time. The high temperature magnetic transitions get broader and suppressed while the low temperature maxima in magnetic susceptibility overshadows the high temperature transition. The field dependent magnetization studies describe the competitive coexistence of antiferromagnetic (AFM) and ferromagnetic (FM) interactions in x = 0.35, whereas for x = 0.40, the magnetic ground state is dominantly AFM. The magnitude of magnetization reduces with milling, which could be explained by core-shell model. Detailed analysis of X-ray diffraction, neutron diffraction, and magnetization studies are presented to understand the role of Bi³⁺ as well as particle size on structure and magnetism.