Manganite charge and orbitally ordered and disordered states probed by Fe substitution into Mn site in LnBaMn1.96Fe0.04O5, LnBaMn1.96Fe0.04O6 and

The layered manganese oxides LnBaMn1.96Fe0.04Oy (Ln=Y, Gd, Sm, Nd, Pr, La) have been synthesized for y = 5, 5.5 and 6. In oxygen-saturated state (y = 6) they exhibit the charge and orbital order at ambient temperature for Ln=Y, Gd, Sm, but unordered eg-electronic system for Ln=La,Pr,Nd. Fourfould increase of quadrupole splitting was observed in charge and orbitally ordered manganites compared to unordered ones. This is in agreement with the jumplike increase of distortion of reduced perovskite-like cell in the charge and orbitally ordered structures. Substitution of 2 percent of Mn by Fe suppresses the temperatures of structural and magnetic transitions by 20 to 50 K. Parameters of crystal lattices and room-temperature Mssbauer spectra were studied on fourty samples whose structures were refined within five symmetry groups: P4/mmm, P4/nmm, Pm3m, Icma and P2. Overwhelming majority of Fe species are undifferentiated by the Mssbauer parameters except special cases. The single-component spectra in two-site structures are explained by preference of Fe towards the site of Mn(III) and by segmentation of charge and orbitally ordered domains.