Mössbauer study of the Fe-dopedLa0.9MnOx manganites

Abstract

The local structure of the 2.5% 57Fe-doped La0.9MnOx (x = 2.89,2.92 and 2.93) manganites has been investigated by means of Mössbauer spectroscopy. In theparamagnetic phase, the Mössbauer spectra of all three samples consist of two quadrupoledoublets which suggest two different iron positions distinguished by their local environment. Ithas been assumed that in the position with a large quadrupole splitting, QS1, theFe3+ is surrounded bysix Jahn–Teller Mn3+ ions. The second iron position with the smaller quadrupole splitting, QS2, correspondsto the manganese environment in which at least one manganese ion is in theMn4+ state. In the magnetically ordered phase, these positions becomeindistinguishable. We conclude that even in the absence ofMn4+ ions the introductionof the non-Jahn–Teller Fe3+ ion in the Mn3+ environment leads to the local removal of static ordering of theMn3+ d3z2−r2 orbitals that result in the ferromagnetic ordering of the Mn spins. The result indicates akey role of the dynamic orbital correlations in the formation of the ferromagnetic orderingin manganites.