Magnetic properties of bismuth(III) oxy compounds

Nuclear quadrupole resonance and SQUID-magnetometric studies on magnetic properties of bismuth(III) oxy compounds comprising neither d- nor f-elements are surveyed and systematised. The magnetic properties, not conventionally expected in the Main Group element substances, were found to exist in most of the compounds discussed. The results of the analysis of the zero-field ²⁰⁹Bi NQR line shapes, the Zeeman-perturbed patterns in external fields of various orientations with respect to the crystal axes, and the spin-echo envelopes suggest the existence in α-Bi₂O₃ , Bi₃O₄Br, Bi₂Al₄O₉ , Bi₂Ge₃O₉ , Bi₄Ge₃O₁₂ , BaBiO₂Cl, of ordered magnetic fields ranging from 30 to 250 G, which notably exceed the dipole nuclear magnetic fields. The magnetoelectric effect was observed in the α-Bi₂O₃ single crystal, and the paramagnetism depending on the thermal prehistory of the crystal was found using a SQUID-technique. The questions concerning the origin of unusual magnetic and electronic properties of the title compounds are discussed.