The impact of bi-phasic crystal structure on the magnetic and transport properties of single crystalline NdBaMn 2 O 5 + δ

The LnBaMn 2 O 5 (Ln = rare-earth) manganites have attracted considerable recent interest due to their potential for use as oxygen storage materials and as solid oxide fuel cells. However, there is scarce data on the magnetic properties of some prototypical materials. Here, we report the synthesis of a single-crystalline NdBaMn 2 O 5 + δ compound by the floating-zone method and investigate its structural, electronic, and magnetic properties. The structural data indicate that, at room temperature, the material consists of a mixture of a NdBaMn 2 O 5 phase with a layered arrangement of the Nd/Ba ions (space group P 4 / n m m ) and a NdBaMn 2 O 6 phase with a disordered distribution of Nd/Ba (space group I m m a ). Measurements of magnetization performed with the magnetic field applied at distinct crystallographic directions reveal a rich magnetic diagram, which is compared with that of similar rare-earth manganites. A peculiar anisotropy is observed between the c axis and the a b plane of the NdBaMn 2 O 5 phase, suggesting a G-type magnetic structure in which the Mn moments are oriented along the a b planes. The electrical transport data show a pronounced magnetoresistance, which is discussed in terms of the system’s crystal structure and the presence of mixed-valent Mn. • Single crystals of NdBaMn 2 O 5 + δ were grown and shown to contain coexisting O5 and O6 phases. • Magnetic data reveal strong anisotropy consistent with G-type order in the O5 phase. • The O6 phase remains at low temperature and contributes a distinct magnetic transition.