The magnetic and neutron diffraction studies of La_1−xSr_xMnO₃ nanoparticles prepared via molten salt synthesis

Series of single-phase La_1−xSr_xMnO₃ nanoparticles (x=0.25−0.47) with the size of about 50 nm was prepared in molten NaNO₂. TEM evidenced well dispersed particles that are not interconnected by sintering bridges in contrast to traditional products. Interestingly, some reduction of the perovskite cell volume, particularly at higher Sr-contents, was detected by XRD. Moreover, reduced magnetization and decreased Curie temperature in comparison to sol–gel samples were observed. Neutron diffraction analysis of the as-prepared nanoparticles and several comparative samples with x=0.37 indicated that the anomalous behavior of studied particles probably originate in the overdoped outer shell. The overdoping might result from both the surface oxygen chemisorption and from an increased Sr concentration in the shell. By all means, the overdoping would lead to compressive surface stress, driving the x=0.37 ground state toward a mixture of FM and A-type AFM ordering as observed by neutron diffraction. - Graphical abstract: La_1−xSr_xMnO₃ nanoparticles with the size of about 50 nm were prepared by newly established method in molten NaNO₂. TEM proved the formation of well-separated particles without sintering bridges, the major advantage over traditional preparation methods. - Highlights: • Series of La_1−xSr_xMnO₃ nanoparticles was prepared by novel method in NaNO₂ melt. • Lower magnetization and Curie temperature in comparison to sol–gel nanoparticles was observed. • Overdoping of outer shell was indicated by neutron diffraction and cerimetric titration. • Overdoping shifts La_0.37Sr_0.63MnO₃ ground state to a mixture of FM and A-type AFM ordering