Mossbauer study of nanocrystalline materials LaFeO₃

Perovskite-type nanocrystalline materials LaFeO₃ with three crystal sizes, 12.4, 16.0 and 70nm, were synthesized. These nanocrystals were then compacted under different axial pressures, 0.5, 1.0 and 1.5 GPa respectively to form samples, which were investigated using an OXFORD MS-500 Mossbauer spectrometer. Results show that the samples consisted of 70 nm LaFeO₃ crystals possesses an antiferromagnetic structure, and those of 12.4 nm a superposition of a weaker antiferromagnetic structure and a stronger superparamagnetic structure. The ratio of interface to crystal atoms and the hyperfine field in nanocrystals vary with compacting pressure. The results obtained on the rotating anode X-ray diffractometer(D/Max-rA, made in Japan) indicate that smashing, contact zone formation and dislocation occur in the samples compacted under all three pressures.