A-site ordered state in manganites with perovskite-like structure based on optimally doped compounds Ln0.70Ba0.30MnO3 (Ln = Pr, Nd)

Abstract

In this paper, we report on the crystal structure and magnetic properties of the nanostructured Ba-ordered phases of rare-earth manganites obtained from the optimally doped solid solutions Ln 0.70 Ba 0.30 MnO 3 (Ln = Pr, Nd). The materials were studied by Xray diffraction, scanning electron microscopy, energy dispersive spectroscopy and SQUIDmagnetometry techniques. It is found that states with different degrees of cation ordering in the A-sublattice of the ABO 3 perovskite can be obtained by employing special conditions of chemical treatment. In particular, reduction of the parent compounds results in the formation of a nanocomposite containing ferrimagnetic anion-deficient ordered phase LnBaMn 2 O 5 . Oxidation of the composite does not change an average size of the nanocrystallites, but drastically alters their phase composition to stabilize ferromagnetic stoichiometric ordered phase LnBaMn 2 O 6 and ferromagnetic superstoichiometric disordered phase Ln 0.90 Ba 0.10 MnO 3+δ . It is shown that the magnetic properties of the materials are determined by the joint action of chemical (cation ordering) and external (surface tension) pressures.

Magnetic Properties of La0.9A0.1MnO3 (A: Li, Na, K) Nanopowders and Nanoceramics

“…The DE mechanism links the electronic properties to the magnetic transition and describes the hopping of electrons in e g orbitals between neighboring Mn 3+ and Mn 4+ ions with strong on-site Hund's coupling by an O 2− anion. To induce the formation of Mn 4+ ions, manganites are doped with either mono- [5,6] or divalent ions [7,8], which, in turn, leads to the compensation of the charge and formation of Mn 4+ in the place of Mn 3+ . A lot of the studies suggest that the ground states of manganites are intrinsically inhomogeneous and characterized by the presence of competing phases extending over domains, especially at the nanoscale [9,10].…”