(La,Sr)(Mn,Me)O_3 manganites doped with d metals: Study of charge compensation mechanisms by crystallographic and magnetic characterizations

摘要

A comparison between theoretically calculated unit cell volume and interatomic distances in the system La_(0.7)Sr_(0.3)Mn_(1-x)Me_xO_(3+delta) (where Me = Cu, Fe, Cr, Ti) and the experimental data obtained by the full-profile Rietveld X-ray analysis as well as an analysis of magnetic properties allowed us to suggest possible mechanisms of charge compensation occurring when d metals substitute for manganese. It has been shown that in the case when copper, iron, chromium and titanium ions substitute for manganese ions in the system La_(0.7)Sr_(0.3)Mn_(1-x)Me_xO_3 charge compensation is described by the model 2Mn~(3+) -> Mn~(4+) + Cu~(2+), Mn~(3+) -> Fe~(3+), Mn~(3+) -> Cr~(3+) and Mn~(4+) -> Ti~(4+), respectively. In the latter case, a decrease in oxygen nonstoichiometry occurs with increasing x.