Manganite charge and orbitally ordered and disordered states probed by Fe substitution into Mn site in LnBaMn1.96Fe0.04O5, LnBaMn1.96Fe0.04O6 and LnBaMn1.96Fe0.04O5.5 (Ln=Y, Gd, Sm, Nd, Pr, La)

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 the 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. Fourfold increase of quadrupole splitting was observed owing to the charge and orbital ordering. This is in agreement with the jumplike increase in distortion of the reduced perovskite-like cell for the charge and orbitally ordered manganites compared to the unordered ones. Substitution of 2 percents of Mn by Fe suppresses the temperatures of structural and magnetic transitions by 20 to 50 K. Parameters of the crystal lattices and the room-temperature M\"{o}ssbauer spectra were studied on forty samples whose structures were refined within five symmetry groups: P4/mmm, P4/nmm, Pm-3m, Icma and P2/m. Overwhelming majority of the Fe species are undifferentiated in the M\"{o}ssbauer spectra for most of the samples. Such the single-component spectra in the two-site structures are explained by the preference of Fe towards the site of Mn(III) and by the segmentation of the charge and orbitally ordered domains.