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

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 Ln0.70Ba0.30MnO3 (Ln = Pr, Nd). The materials were studied by X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy and SQUID magnetometry techniques. It is found that states with different degrees of cation ordering in the A- sublattice of the ABO3 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 LnBaMn2O5. 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 LnBaMn2O6 and ferromagnetic superstoichiometric disordered phase Ln0.90Ba0.10MnO3+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.