SYNTHESIS, STRUCTURE, AND MAGNETIC-PROPERTIES OF THE LAYERED BISMUTH TRANSITION-METAL OXIDE SOLID-SOLUTION BI2FE4-XGAXO9

The solid solution Bi2Fe4-xGaxO9 (0 ≤ x ≤ 4) was was synthesized and investigated by X-ray diffraction, Moössbauer spectroscopy, and susceptibility measurements. The system was found essentially to follow Vegard's law. The crystal structure of thex = 2 member, Bi2Fe2Ga2O9, was solved. The structure is orthorhombic with space group Pbam (No. 55), a = 7.946(1)Å, b = 8.355(1)Å, and c = 5.929(1)Å. Iron and gallium were nonstatistically distributed over two octahedral and two tetrahedral sites. The iron displayed a 60% preference for the octahedral positions. Magnetic susceptibility and Moössbauer measurements showed antiferromagnetic behavior. The ordering temperature, TN, exhibited a strong dependence on x, decreasing rapidly with gallium doping from TN = 245 ± 5K for x = 0 to TN < 4.2K for x = 3. Spin-glass-like behavior was observed in the gallium-substituted compounds, and a previously undetected spin rearrangement at 220 K for the x = 0 compound is reported. © 1992 Academic Press, Inc. All rights reserved.