Local Magnetic Fields in Diamagnetic BiSbO₄ and Bi₄Si₃O₁₂: ²⁰⁹Bi NQR

Local magnetic fields H_loc exceeding significantly the magnetic fields produced by nuclear magnetic moments (a few gauss) have been detected in bismuth compounds with valence s and p electrons, which are generally believed to be diamagnetic, by the methods based on measuring the parameters of nuclear quadrupole interactions. Anomalies in the magnetic properties of BiSbO₄ and Bi₄Si₃O₁₂ were clearly manifested when analyzing the line shapes in their ²⁰⁹Bi NQR spectra. The quartet of lines for the lower transition ν₁ (Δm = 1/2–3/2) in the spectrum of Bi₄Si₃O₁₂ in zero external magnetic field and the doublets for the lines of all other transitions in the spectrum of BiSbO₄ at unique crystallographic positions of bismuth atoms in the crystal lattices of the compounds suggest a magnetic nature of the splittings. The most probable values of H_loc in these compounds are those in the range from 40 to 100 G.