Mössbauer spectrum of high-pressure synthesized ilmenite-type FeGeO₃

Ilmenite-type FeGeO₃ was prepared by high-pressure synthesis technique using a Kawai-type multi-anvil apparatus at 23.5 GPa and 500 °C. The effects of post annealing on the high-pressure synthesized samples were investigated by XRD analysis, Mössbauer spectroscopy and SQUID-magnetization measurements. The subsequent annealing after the high-pressure synthesis was effective to improve the crystallinity and increased the crystallite size of the ilmenite-type FeGeO₃. The room temperature Mössbauer spectrum was composed of sharp paramagnetic doublets assigned to Fe²⁺. The well-crystallized ilmenite-type FeGeO₃ showed typical antiferromagnetic behavior with the Néel temperature of 79 K, while the as-prepared sample without annealing demonstrated the superparamagnetic characteristics with larger magnetization.