Magnetic properties of amorphous-like oxides of the Bi 2O 3-Fe 2O 3-PbTiO 3 system synthesized by sol-gel method

Abstract

Similar to films rf-sputtered in an argon and oxygen mixed gas, amorphous-like oxides (films and powders) with the ternary Bi 2O 3-Fe 2O 3-PbTiO 3 system prepared by sol-gel method develop a considerably large spontaneous magnetization after being annealed above T a = 500 °C in air. The magnetization of gel-coated films showed a sharp maximum I S exceeding 0.1 T in a narrow region with the Fe 2O 3-rich compositions when annealed around T a = 700 °C, where samples showed halo-patterns in X-ray diffraction, retaining the amorphous state, while further increase in Ta results in a rapid decrease in magnetization, where X-ray diffraction lines assigned to para- and/or antiferromagnetic oxide precipitates such as α-Fe 2O 3, BiFeO 3, and Bi 2Fe 4O 9, were apparent. It may be concluded that spontaneous magnetization arises from nano-ferrimagnetic clusters which cannot be detected by X-ray diffraction. In order to elucidate its microscopic origin, Mössbauer measurement was also carried out.