MODIFIED THEORY FOR MÖSSBAUER SPECTRA OF SUPERPARAMAGNETIC PARTICLES : APPLICATION TO Fe3O4

S. MØRUP, H. TOPSØE, J. LIPKA
1976 Le Journal de Physique Colloques  
R&um6. -L'article presente un modkle modifie pour relaxation superparamagnetique. Ce modkle associe le superparamagnetisme conventionnel avec l'effet, dernierement decrit, des excitations collectives de l'aimantation autour d'une direction facile. I1 y a aussi une discussion des effets prononces de granulometrie. Le modele explique la valeur rkduite des domaines hyperfins observes, ainsi que les formes de raies asymetriques de spectres Mossbauer de petites particules de composes arranges selon
more » ... eur magnetisme. L'adsorption chimique de molCcules diffkrentes sur particules de Fe304 indique que l'energie anisotropique est sensible aux effets de surface. Abstract. -A modified model for superparamagnetic relaxation is presented. This model combines the conventional superparamagnetism with the recently described effect of collective excitations of the magnetization around an easy direction. The marked effects of particle size are also discussed. The model explains the reduced value of the observed hyperfine fields and the asymmetric line shapes of Mossbauer spectra of small particles of magnetically ordered compounds. Chemisorption of different molecules on Fe304 particles shows that the anisotropy energy is sensitive to surface effects.
doi:10.1051/jphyscol:1976658 fatcat:j6s2uc6ovjce7h2ppy3lwwk4e4