Multiferroic bismuth ferrite: Perturbed angular correlation studies on its ferroic α − β phase transition

• Published in: Physical review. B 2020-12, Vol.102 (22), p.1, Article 224110
• Main Authors: Marschick, G., Schell, J., Stöger, B., Gonçalves, J. N., Karabasov, M. O., Zyabkin, D., Welker, A., Escobar C., M., Gärtner, D., Efe, I., Santos, R. A., Laulainen, J. E. M., Lupascu, D. C.
• Format: Article
• Language: English
• Subjects: Angular correlation; Beta phase; Bismuth ferrite; Correlation analysis; Crystal structure; Electric fields; Ferroelectricity; High temperature; Mathematical analysis; Multiferroic materials; Parameters; Perovskites; Phase transitions; Quadrupoles; Symmetry; Temperature; Temperature dependence; Transition temperature
• ISSN: 2469-9950; 2469-9969
• DOI: 10.1103/PhysRevB.102.224110

Work of numerous research groups has shown different outcomes of studies of the transition from the ferroelectric α -phase to the high temperature β -phase of the multiferroic, magnetoelectric perovskite Bismuth Ferrite ( BiFeO 3 or BFO). Using the perturbed angular correlation (PAC) method with 111 m Cd as the probe nucleus, the α to β phase transition was characterized. The phase transition temperature, the change of the crystal structure, and its parameters were supervised with measurements at different temperatures using a six detector PAC setup to observe the γ − γ decay of the 111mCd probe nucleus. The temperature dependence of the hyperfine parameters shows a change in coordination of the probe ion, which substitutes for the bismuth site, forecasting the phase transition to β -BFO by either increasing disorder or formation of a polytype transition structure. A visible drop of the quadrupole frequency ω 0 at a temperature of about Tc ≈ 820 ∘ C indicates the α − β phase transition. For a given crystal symmetry, the DFT-calculations yield a specific local symmetry and electric field gradient value of the probe ion. The P b n m ( β -BFO) crystal symmetry yields calculated local electric field gradients, which very well match our experimental results. The assumption of other crystal symmetries results in significantly different computed local environments not corresponding to the experiment.