We present the study of the effect of crystal growth atmosphere (argon or air) and chemical doping (iron) on the quality and oxygen nonstoichiometry of the single crystals with the general formula NdMn1-xFexO3+delta, which were grown by the optical floating zone method. The analysis of the grown ingots showed that in the Ar atmosphere the losses of the oxygen lead to MnO impurities, but in the air atmosphere some Mn3+ ions are replaced by Mn4+ ions (thence we have observed positive delta). The X-ray Laue diffraction and polarized light microscopy revealed that the twinning of the grown ingots is the common phenomenon. This twinning can be explained by the fact that a/c similar to 1. Neutron diffraction experiment revealed that the preferential growing directions of the compound are (101) and (010). (C) 2013 Elsevier B.V. All rights reserved,