Nanocrystalline NiFe2O4 spinel has been synthesized with various grain sizes by high-energy ball milling. From the high-field magnetization studies and extended x-ray-absorption fine-structure, and Mössbauer measurements in an external magnetic field of 5 T applied parallel to the direction of gamma rays, we could observe that Ni2+ ions occupy tetrahedral sites on grain-size reduction due to milling. The Fe3+ spins have a canted structure and the canting angle increases with grain-size reduction. It is possible that the core Fe3+ spins are also canted because of the magnetocrystalline anisotropy introduced by the occupancy of the Ni2+ ions in the tetrahedral sites.
Physical Review B
- Pub Date:
- May 2001
- Nanoscale materials and structures: fabrication and characterization;
- Powder processing: powder metallurgy compaction sintering mechanical alloying and granulation;
- Mossbauer effect;
- other gamma-ray spectroscopy