Nanocomposites and nanomaterials
Crystal structure and orbital ordering of BiMnO3+δ (0 < δ < 0.14) compounds across the phase boundary
D.V. Karpinsky1*, S.I. Latushka1, D.V. Zhaludkevich1, A.N. Chobot1,
V.V. Sikolenko2, B.N. Savenko2, T.V. Latushka3, O.P. Budnyk4, O.M. Fesenko4
1Scientific-Practical Materials Research Centre of NAS of Belarus, 220072 Minsk, Belarus
* e-mail: dmitry.karpinsky@gmail.com
2Joint Institute for Nuclear Research, 141908 Dubna, Russia
3Belarusian State Medical University, 220116 Minsk, Belarus
4Institute of Physics, National Academy of Sciences of Ukraine, 03028 Kyiv, Ukraine
In the last decade, complex oxides of transition metals, such as bismuth ferrite [1] and bismuth manganite [2], which are characterized by strong correlation between crystal structure, electric and magnetic properties have attracted increased interest among researchers. Various chemical doping schemes can be used to controllably modify functional properties of these compounds [3]. 
Multiferroic compounds BiMnO3+δ with a nominal excess of oxygen δ = 0.02, 0.08, 0.14 were prepared from high purity oxides using a high-pressure high temperature technique. An effect of the nominal excess of oxygen on the structural state of the BiMnO3+δ compounds was studied by X-ray structural analysis method. The X-ray diffraction data obtained for the compounds have showed that an increase in the nominal concentration of oxygen ions leads to the next sequence of the phase transitions, viz. from the monoclinic structure (C2/c) specific for the compound BiMnO3.02 to the monoclinic (P21/c) attributed to the compound BiMnO3.08 and then to the orthorhombic structure (Pnma) for the compound BiMnO3.14 through the formation of a two-phase structural state. The indicated sequence of phase transitions is accompanied by a gradual destruction of the orbital ordering formed by the d3z2-r2 orbitals of Mn3+ ions, which is caused by the nonuniform distribution of manganese ions vacancies in the B-position of the perovskite lattice.
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This work was supported by European Union’s Horizon 2020 research and innovation programme (RISE No. 778070), BRFFR (# Т20R-121) and RFBR (# 20-52-00023).