Size dependence of the properties of hematite nanoparticles

F. Bødker; S. Mørup

doi:doi:10.1209/epl/i2000-00426-2

DOI: 10.1209/epl/i2000-00426-2

Europhys. Lett., 52 (2), p. 217 (2000)

Size dependence of the properties
of hematite nanoparticles

F. Bødker - S. Mørup

Department of Physics, Building 307, Technical University of Denmark
DK-2800 Kgs. Lyngby, Denmark

(Received 10 July 2000; accepted 21 August 2000)

PACS :
75.50.Tt - Fine-particle systems
76.60.Es - Relaxation effects
76.80.+y - Mössbauer effect; other $\gamma$ -ray spectroscopy

Abstract:

Samples of nanoparticles of hematite $(\alpha$ - Fe₂O₃) with average size between 6 and 27 nm have been studied by use of Mössbauer spectroscopy. The superparamagnetic relaxation was analysed on the basis of the Néel-Brown expression for the relaxation time, $\tau = \tau_0 \exp[KV/kT]$ . It was found that the value of $\tau_0$ increases with increasing particle volume, V, whereas the magnetic anisotropy energy constant, K, decreases. The electric quadrupole interaction, the isomer shift and the magnetic hyperfine field extrapolated to 0 K were found to be essentially independent of particle size.

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