Magnetic order in γ-Fe2O3 nanoparticles: a XMCD study

S. Brice-Profeta (1) , M.-A. Arrio (1) , E. Tronc (2) , N. Menguy (1) , I. Letard (1) , C. Cartier (3, 4) , M. Noguès (5) , Corinne Chanéac (2) , Jean-Pierre Jolivet (6) , Ph. Sainctavit (1, 4)

1 LMCP - Laboratoire de minéralogie, cristallographie de Paris
2 LCMCP (site Paris VI) - Laboratoire de Chimie de la Matière Condensée de Paris (site Paris VI)
3 CIM2 - Laboratoire de Chimie Inorganique et Matériaux Moléculaires
4 LURE - Laboratoire pour l'utilisation du rayonnement électromagnétique
5 LMOV - Laboratoire de magnétisme et d'optique de Versailles
6 LCMCP - Laboratoire de Chimie de la Matière Condensée de Paris

Spin-canting in spinel nanoparticles of maghemite has multiple origins, among which surface effects, finite-size effects or chemical disorder effects. XMCD at the Fe L2,3 edges allows to separate the contributions of the magnetic moments of Fe3+ ions in tetrahedral and octahedral sites of γ-Fe2O3. We investigate three powders of γ-Fe2O3 synthetized via aqueous precipitation: particles of average diameter 2.7, 8 nm and particles of average diameter 8 nm coated with phosphoric acid. The relative contributions of the spins of the Click to view the MathML source and the Click to view the MathML source ions are observed, varying the external magnetic field. Under high magnetic fields, a reduction of the magnetic contribution of the Click to view the MathML source ions occurs for 8 nm phosphate-coated particles by comparison with the uncoated ones. A similar reduction appears at lower magnetic fields for the small 2.7 nm particles.

Mots clés: 3 edges; Iron L2; Spin-canting; XMCD; γ-Fe2O3; Maghemite nanoparticles

Domaines: Science des matériaux [cond-mat.mtrl-sci]

S. Brice-Profeta, M.-A. Arrio, E. Tronc, N. Menguy, I. Letard, et al.. Magnetic order in γ-Fe2O3 nanoparticles: a XMCD study. Journal of Magnetism and Magnetic Materials, 2005, 288, pp.354-365. ⟨10.1016/j.jmmm.2004.09.120⟩. ⟨hal-00112611⟩