TDPAC measurements in Bismuth Ferrite

In this report we present a study of local magnetoelectric effect at the Bi-site in multiferroic bismuth ferrite (BiFeO3 or BFO) by means of time differential perturbed angular correlation (TDPAC) spectroscopy. The main approach is to use the 111mCd (111Cd) probe, produced at ISOLDE-CERN, as a tracer ion for the investigation of the hyperfine interactions. The TDPAC measurements were carried out at various temperatures ($15 – 500^{\circ}C$) after thermal treatment at $800^{\circ}C$ in air for 20 minutes. The resulting TDPAC spectra show the absence of magnetoelectric coupling at the site of the bismuth ion in the antiferromagnetic phase of BFO, i.e. below the Néel temperature. This key investigation experimentally confirms that the super-exchange interaction between the two Fe ions is broken with the presence of the 111mCd probe. Moreover, the substitutional Bi-site location of the probe is confirmed using ab-initio density functional theory (DFT) simulations.