CHARACTERIZATION OF ELECTRIC FIELD GRADIENT ANISOTROPY AND INTERNAL MAGNETIC FIELDS IN BISMUTH-CONTAINING COMPOUNDS

This study investigates the anisotropy of electronic density and local magnetic fields in bismuth oxide and bismuth oxyhalide compounds using nuclear quadrupole resonance (NQR) spectroscopy of the 209Bi nucleus. Although these materials are conventionally classified as diamagnetic, the experimental results reveal the presence of ordered internal magnetic fields reaching up to 250 Gs. NQR spectra obtained from α-Bi2O3, Bi5O4Br, Bi4Al4O9, Bi₄Ge₃O₁₂, and Bi₂Ge₃O₉ were analyzed through spectral processing, mathematical modeling, and evaluation of quadrupole interactions. The influence of electric field gradient anisotropy and Zeeman splitting on resonance line structure was examined in detail. The results demonstrate that nonequivalent crystallographic positions of bismuth atoms lead to significant variations in quadrupole parameters and local magnetic environments. Comparative analysis of spectral line broadening and splitting confirms the sensitivity of the NQR method to subtle electronic and magnetic interactions. The obtained findings provide valuable information about the electronic structure of bismuth-containing functional materials and establish a basis for further investigations of local magnetic ordering and crystal-field effects.