Springer LINK: The European Physical Journal B - Abstract Volume 5 Issue 4 (1998) pp 859-867

The European Physical Journal B

ISSN: 1434-6028 (printed version)
ISSN: 1434-6036 (electronic version)

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Abstract Volume 5 Issue 4 (1998) pp 859-867

Static magneto-optical birefringence of size-sorted ${\vec\gamma}\sf {-}Fe_2O_3$ nanoparticles

E. Hasmonay (1), E. Dubois (2), J.-C. Bacri (1) (a), R. Perzynski (1) (b), Y.L. Raikher (3), V.I. Stepanov (3)

(1) Laboratoire des Milieux Désordonnés et Hétérogènes, Université Pierre et Marie Curie, Tour 13, Case 78, 4 place Jussieu, 75252 Paris Cedex 05, France
(2) Laboratoire des Liquides Ioniques et Interfaces Chargées, Université Pierre et Marie Curie, Bâtiment F, Case 63, 4 place Jussieu, 75252 Paris Cedex 05, France
(3) Laboratory of Kinetics of Anisotropic Fluids, Institute of Continuous Media Mechanics, Urals Branch of the Russian Academy of Sciences, 1 Korolyov St., Perm 614013, Russia

Received: 9 January 1998 / Received in final form and Accepted: 5 May 1998

Abstract: Magnetic birefringence experiments under static field are performed on ionic ferrofluid samples based on $\gamma$-Fe₂O₃. A colloidal size-sorting of the particles allows to obtain narrow size distributions. The optical birefringence of the solutions is found positive and can be described by a Langevin formalism. It scales as H² in the low field limit. In the high field limit the particles size dependence of the saturation birefringence is compatible with a surface anisotropy constant $K_S= 2.8\times 10^{-2}$ erg cm^-2 associated with a particle elongation of 1.25 both coherent with Néel predictions of surface anisotropy in small grains.

PACS. 75.50.Mm Magnetic liquids - 78.20.Ls Magnetooptical effects - 78.66.J Nanocrystalline materials, optical properties

(a) Also at: Université Denis Diderot (Paris VII), UFR de Physique, 2 place Jussieu, 75251 Paris Cedex 05.
(b) email: rperz@ccr.jussieu.fr

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