Laboratoire Léon Brillouin
UMR12 CEA-CNRS, Bât. 563 CEA Saclay
91191 Gif sur Yvette Cedex, France
+33-169085241 llb-sec@cea.fr
Spatial distributions of the magnetization of Bi2Fe4O9 projected along the c axis measured with polarized neutrons under a magnetic field of 6T applied along c at T=250K
K. Beauvois, V. Simonet, S. Petit, J. Robert, F. Bourdarot, M. Gospodinov, A.A. Mukhin, R. Ballou, V. Skumryev, and E. Ressouche
The research field of magnetic frustration is dominated by triangle-based lattices but exotic phenomena can also be observed in pentagonal networks. A peculiar noncollinear magnetic order is indeed known to be stabilized in Bi2Fe4O9 materializing a Cairo pentagonal lattice. We present the spin wave excitations in the magnetically ordered state, obtained by inelastic neutron scattering. They reveal an unconventional excited state related to local precession of pairs of spins. The magnetic excitations are then modeled to determine the superexchange interactions for which the frustration is indeed at the origin of the spin arrangement. This analysis unveils a hierarchy in the interactions, leading to a paramagnetic state (close to the Néel temperature) constituted of strongly coupled dimers separated by much less correlated spins. This produces two types of response to an applied magnetic field associated with the two nonequivalent Fe sites, as observed in the magnetization distributions obtained using polarized neutrons.
• Physics, chemistry, nanoscience and materials around large instruments › Physique de la matière condensée, étude par l’interaction rayonnement matière
Physique, chimie, nanosciences et matériaux autour des grands instruments
• Laboratoire Léon Brillouin (LLB) • Leon Brillouin Laboratory (LLB)
• Groupe "Matière molle et biophysique" - MMB • Nouvelles frontières dans les matériaux quantiques - NFMQ • Magnetism, Frustration and Disorder
• Neutrons • Activités instrumentales nationales et internationales du LLB - National and internatonial instrumental activities at the LLB • Neutrons • Inelastic scattering • Les 3 axes