Magnetic properties of anion deficit manganites Ln0.55Ba0.45MnO3-γ (Ln=La, Nd, Sm, Gd, γ≤0.37)

A detailed study of oxygen deficit effect on magnetic properties was carried out for Ln0.55Ba0.45MnO3-γ (Ln=La, Nd, Sm, Gd). It was shown that Ln0.55Ba0.45MnO3-γ undergoes a concentrational phase transition from ferromagnetic to spin glass state at γ=0.15. The freezing temperature Tf decreases with decreasing oxygen content down to 80 K for γ=0.37. Another behavior has been revealed for Ln=Nd, Sm, Gd series; these compounds undergo a transition from ferromagnetic state (Ln=Nd) or spin-glass one (Ln=Sm, Gd) into weak ferromagnetic state (γ=0.35) through intermediate antiferromagnetic state (γ=0.2). In contrast to stoichiometric manganites the Neel point increases from 136 K (Ln=Nd) to 160 K (Ln=Gd) with decreasing rare-earth ionic radii. It is supposed that both lanthanide and barium ions as well as oxygen vacancies are ordered in the strongly reduced rare-earth manganites