Abstract
Uniform hematite particles with an average size of 400 Å were prepared for reducing the influence of the particle-size distribution on the measurement of the Morin temperature. A series of Mössbauer spectra at different temperatures have been recorded. The Morin transition occurs at 216 K for sample B coated with a surfactant-oleic acid, and it occurs at 192 K for uncoated sample A. The temperature intervals in the region of the spin flip are almost the same for both samples. These results show that aT m shift could arise from surface effects such as spin pinning directly induced by a surfactant, and that the distortion produces restriction not only on the top few layers, but also on the whole volume of the particle.
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Kumar, L., Fan, Y.Z., Hu, B.Y. et al. Surface effect on the Morin transition of α-Fe2O3 particles coated with surfactant. Hyperfine Interact 84, 137–141 (1994). https://doi.org/10.1007/BF02060654
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DOI: https://doi.org/10.1007/BF02060654