Study of the crystal and electronic structures of (Bi_1−xNd_x)FeO₃ compositions using Rietveld refinements and the maximum entropy method

Abstract

In this work we present a methodology that combines the Rietveld structure refinement and the Maximum Entropy Method (MEM) to analyze the crystal and electronic structures, and the chemical bonding of the Bi_1−xNd_xFeO₃ compositions for x = 0.025, 0.05, 0.075, 0.10, 0.15 and 0.20. A structural phase modification from rhombohedral R3c to orthorhombic (Pnma) was observed with the increase in the neodymium content. As an intermediate phase in the transition from R3c to Pnma, a monoclinic structure (C2/m) took place. Electron density calculations provided the observation of a total suppression of the covalent bonds between the bismuth and oxygen ions for x = 0.10 and the emergence of the covalent character between all the bonds for x = 0.20.

KEYWORDS:

• Magnetoelectric
• BiFeO₃
• Rietveld refinement
• maximum entropy method

Acknowledgements

OGO and AJM thank CAPES for the fellowship. AJM thanks the NSF/INAMM program at UTSA under the PDSE program for hosting him. Authors also thank Brazilian Synchrotron Light Laboratory for the X-ray diffraction measurements.

Additional information

Funding

The authors would like to thank the Brazilian funding agencies CAPES (proc. 174363 Procad 071/2013 and Procad 88881.068509/2014-01) and CNPq (procs. 445837/2014-4, 301991/2015-4, 200977/2015-6, 309830/2017-6, 446565/2014-8, and 429687/2016-8) for financial support.