An Order-Disorder Transformation Phenomenon in the FeTiO₃–Fe₂O₃ Solid Solution Series

抄録

The effects of heat treatments on the magnetic properties of the synthesized solid solution xFeTiO₃–(1−x)Fe₂O₃ of ilmenite and hematite were examined in detail for compositions x around 0.5. It was confirmed that a transformation from an ordered state (ferrimagnetic one) into a disordered state (antiferromagnetic one) takes place cooperatively at a distinct transition point. This transformation temperature is lowered with decrease in the ilmenite content from 1100°C for x=0.65 to 600°C for x=0.45. The completely disordered specimens could not be obtained for the composition x≥0.6 by the quench method while the completely ordered state could not be attained in the specimens with x≤0.5 because of decrease of the transformation temperature for these specimens and a reduction of the rate of ion diffusion at such low temperatures. The results obtained were discussed by using the Bragg-Williams approximation. It was noted briefly that the reverse thermo-remanent magnetism found in this system is closely related to the order-disorder transformation phenomenon which exists in this system.