Effect of Bi³⁺on magnetic properties of nanosized La_0.7-xBi_xSr_0.3MnO₃

Nanoparticles of La_0.7-xBi_xSr_0.3MnO₃(0=x=0.40) manganites, prepared by high energy planetary ball mill using the top-down approach, have been subjected to structural and magnetization studies to understand the influence of Bi³⁺substitution. In the present work, we compare the properties of nanoparticles of all compositions prepared by milling up to 48h. The structural analysis carried out on the X-ray diffractograms using Rietveld refinement method suggest that as Bi³⁺content increases, the structure changes from rhombohedral (space group R-3c, in hexagonal setting) for× »=0.20 to orthorhombic (space group Pnma) for× »=0.30. We also find that the particle size of~17nm observed in× »=0.0 sample, increases to~40nm for× »=0.35 sample. It is interesting to note that along with changes in the structure and particle size, we observe a cross-over from ferromagnetism (FM) in× »=0.0 (T_C=370K) to antiferromagnetism (AFM, for× »=0.40). With increase in Bi³⁺, FM decreases and AFM evolves in the system. For× »=0.40, no long-range ferromagnetism has been noticed. The observed changes in the structural and physical properties could be attributed to the 6s lone pair character of Bi³⁺ions. In the present work, details of structural analysis and magnetization measurements will be presented and discussed.