Topological Analysis of the Experimental Electron Density in Multiferroic Antiferromagnet Ba2MnGe2O7

Abstract

In the field of magnetoelectric coupling, especially via the spin dependent metal-ligand d-p hybridization mechanism found in multiferroic Ba2MGe2O7 (M = Mn, Co), a detailed knowledge of the microscopic structural parameters is essential, also for the theoretical modeling. In this article, we report a systematic structural study of Ba2MnGe2O7 single crystal under varying temperature between 110 to 673 K using non-destructive in-situ single crystal synchrotron radiation diffraction. The maximum entropy method was applied to the X-ray diffraction data for the determination of the deformation in the electron density and the orbital hybridization between the 3d of Mn and 2p of O in the Mn-O bond. Within this entire temperature range, the structure was described in a single crystallographic space group P421m and no structural phase transition has been detected. Interestingly, the forbidden reflections, which arise from multiple diffraction so called “Renninger effect”, were observed at all temperatures without any symmetry lowering. The changes in the structural parameters (bond-lengths, bond-angles, anisotropic displacement parameters and electron density distributions of the atoms) with temperature are revealed, helping to understand some aspects comprising orbital hybridization in multiferroic Ba2MnGe2O7.