Size-induced changes of structural and ferromagnetic properties in La1-xSrxMnO3 nanoparticles

摘要

La1-xSrxMnO3 nanocrystals were grown using a microemulsion approach with different water-to-surfactant ratios R-w resulting in diameters between 20 and 40 nm. The variation of Rw entails a variation in the Sr concentrations between x = 0.35 and 0.50. This technique allows the controlled growth of structurally well-defined nanoparticles using the same calcination conditions. With decreasing particle size, the unit-cell volume increases together with the Mn-O bond length, while the Mn-O-Mn bond angle was found to decrease. The size-dependent change of structural properties is possibly related to surface effects or disorder. With the decrease in particle size, the ferromagnetic ordering temperature T-C decreases significantly by up to 20. The reduction of T-C can be well understood with respect to the structural changes: the increase of Mn-O bond length and the decrease of Mn-O-Mn bond angle weaken the double-exchange coupling and hence reduce T-C. In addition the intrinsic finite-size effect reduces T-C. The observed size-induced change of magnetic properties may allow for a controlled manipulation of magnetism in La1-xSrxMnO3 nanoparticles by varying the particle size. Published by AIP Publishing.