YBaMn 2O 5: crystal and magnetic structure reinvestigation

Abstract

The ordered oxygen-deficient perovskite YBaMn 2O 5 has been synthesized as a monophasic sample. A variable temperature neutron diffraction study of this phase has been carried out. The crystal structure of this manganite was solved in the space group P4/ nmm ( a = 5.547 Å and c = 7.649 Å). This oxide, which is closely related to the YBaCuFeO 5 structure, forms an alternate stacking of yttrium and barium layers along the c axis. It differs from the latter, however, by the existence of two distinct sites for manganese, corresponding to an ordering of the Mn 3+ and Mn 2+ cations, respectively. Elucidation of the magnetic structure of YBaMn 2O 5, from low temperature PND (powder neutron diffraction) data, leads to a G-type antiferromagnetic model; the superimposed Mn 2+/Mn 3+ charge order results in ferrimagnetic behavior for this phase and explains its magnetic properties, as obtained from susceptibility measurements.