Study of the magnetic properties of La0.53Tb0.14Sr0.33MnO3±δ sintered in different conditions

We report the study of the magnetic properties of the manganite compounds of La0.53Tb0.14Sr0.33MnO3±δ sintered in Ar, N2 and O2 atmospheres. The crystal structure and ferromagnetic-paramagnetic transition region are considerably altered for the prepared samples, indicating the expected variation in the concentration of Mn3+ and Mn4+ ions, which was attributed to the oxygen stoichiometric effects. The AC susceptibility and DC magnetization measurements for the prepared samples indicate a cluster-glass state in low magnetic field at low temperatures, besides their respective spin freezing temperatures are similar in spite of the fact that the double-exchange and superexchange interactions are considerably altered. This result induces us to believe that this behavior does not depend only on the competition between those interactions, but also on the interaction between the Mn and Tb moments, since it was found to be a sort of antiferromagnetic ordering below 66 K at 5 kOe applied field. This ordering was ascribed to the Tb moments, suggesting that those are aligned opposite to Mn moments. The obtained magnitude of the saturation magnetization can be explained considering a ferromagnetic alignment of Mn and Tb moments under high fields