Half Replacement of Bismuth by Neodymium in Half-Hole Doped Bismuth-Based Manganites Bi0.25Nd0.25X0.5MnO3 (X = Sr, Ca): a Neutron Diffraction Study

The effect of half substitution of diamagnetic Bi3+ with the rare earth magnetic Nd3+ ion on the magnetic and structural properties of the polycrystalline Bi0.25Nd0.25Sr0.5MnO3 and Bi0.25Nd0.25Ca0.50MnO3 was studied by X-ray and neutron diffraction complemented by magnetic measurement. We correlate the structural response of Bi0.25Nd0.25X0. 5MnO3 (X = Sr, Ca) for charging and spin ordering with a reduced amount of Bi3+, which in addition to its special contribution to itinerant eg electrons leads to a change in the average size of the A-site cations, 〈rA〉, and the mismatch between the A-site cations (size variance, σ 2). For both compounds, the corresponding charge ordering scheme and ground magnetic state of CE-type antiferromagnetic arrangement at 10 K were specified. An analysis of the data confirms that in Bi–Sr manganite a lone pair of 6s2 Bi3+ orbitals is dominant.