Diffusive motion of iron microcrystals studied by Mössbauer spectroscopy

α-Fe nanopowder synthesised in low-pressure microwave plasma and studied by Mössbauer spectroscopy

“…The MS measured at 5 K (with broader lines due to the vibrations caused by the closed cycle cryostat) could be better fitted with: It can be seen that the absorption in the MS measured at 5 K is seven times stronger than in the MS measured at 293 K, which is a large effect rarely observed. The anomalous decrease of the absorption at 293 K can be caused by diffusive tilting motions of nanoparticles as it was already suggested [21]. Similar decrease was observed for a nanopowder synthesised by laser induced pyrolysis [22].…”

The spin-canting anomaly in ferrimagnetic particles

“…Since magnetic recording particles are produced by oxidation of Fe304, and since both samples examined here show haematite, the presence of a haematite coating on the surface of fine particles is likely to be pervasive. Fine oxide crystallites on the surface of a particle are known to exhibit strongly decreasing zero-phonon fractions at temperatures increasing from 4.2 K to room temperature [8,13,141, an effect which explains the two-fold reduction in the apparent spincanting effect for y-Fe203 with a 5 T field applied at 300 K compared to 4.2 K [16].…”

Magnetic Properties of γ-Fe2O3Nanopowder Synthesized by Atmospheric Microwave Torch Discharge

“…The broader lines observed at 5 K were due to the vibrations of the closed cycle cryostat. The anomalous decrease of the absorption at 293 K is attributed to a large portion of particles, which can thermally move, and the chain-like morphology of interconnected particles, which enables diffusive tilting motions of particles [8]. This way the probability of resonance absorption of γ-radiation on 57 Fe nuclei is lowered.…”