A temperature and magnetic field dependence Mössbauer study of ɛ-Fe2O3

Jean Luc Rehspringer (1) , Serge Vilminot (1) , Daniel Niznansky (2) , K. Zaveta (2) , Claude Estournès (3) , Mohamedally Kurmoo (4)

1 IPCMS - Institut de Physique et Chimie des Matériaux de Strasbourg
2 UK - Univerzita Karlova [Praha, Česká republika] = Charles University [Prague, Czech Republic]
3 CIRIMAT - Centre interuniversitaire de recherche et d'ingenierie des matériaux
4 Laboratoire de Chimie de Coordination Organique

ɛ-Fe2O3 was synthesized as nanoparticles by a pre-vacuum heat treatment of yttrium iron garnet (Y3Fe5O12) in a silica matrix at 300-C followed by sintering in air at 1,000-C for up to 10 h. It displays complex magnetic properties that are characterized by two transitions, one at 480 K from a paramagnet (P) to canted antiferromagnet (CAF1) and the second at ca. 120 K from the canted antiferromagnet (CAF1) to another canted antiferromagnet (CAF2). CAF2 has a smaller resultant magnetic moment (i.e. smaller canting angle) than CAF1. Analysis of the zero-field Mossbauer spectra at different temperatures shows an associated discontinuity of the hyperfine field around 120 K. In an applied field, the different magnetic sublattices were identified and the directions of their moments were assigned. The moments of the two sublattices are antiparallel and collinear at 160 K but are at right angle to each other at 4.2 K.

Mots clés: Mössbauer spectra; nanoparticles; complex magnetic properties

Domaines: Matériaux

Jean Luc Rehspringer, Serge Vilminot, Daniel Niznansky, K. Zaveta, Claude Estournès, et al.. A temperature and magnetic field dependence Mössbauer study of ɛ-Fe2O3. Hyperfine Interactions, 2005, 166 (1-4), pp.475-481. ⟨10.1007/s10751-006-9311-8⟩. ⟨hal-03601244⟩