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Statut Confirmé
Domaines cond-mat
Date Lundi 10 Mai 2010
Heure 10:30
Institut IMPMC
Salle Salle de conférence, Bâtiment 15, 140 rue de Lourmel, 75015 Paris
Nom de l'orateur Gauzzi
Prenom de l'orateur Andrea
Addresse email de l'orateur
Institution de l'orateur IMPMC
Titre Crystallographic evidence of a coupling between magnetic and ferroelectric order parameters in bimn7o12
Résumé Manganese oxides AMn7O12 (A=Na, Ca, La) with quadruple perovskite structure display charge, spin and magnetic orderings not observed in simple perovskites. Here we study the magnetic structure of the single-valent compounds LaMn7O12 and BiMn7O12, the quadruple perovskite counterpart of simple perovskites LaMnO3 and BiMnO3, respectively. By means of a neutron diffraction study, we found that in both compounds the A’ and B ions order antiferromagnetically (AFM) at low temperatures in an independent fashion. However, in spite of the common Mn3+ properties, the magnetic structures are strikingly different in the two compounds. In particular, in LaMn7O12 the structure of the B-site is of C-type, which contrasts the A-type structure reported for LaMnO3. On the other hand, in BiMn7O12, the AFM structure of the B-site is characterized by two distinct propagation vectors (1/2,0,1/2) and (0,0,0). We discuss the origin of these differences in terms of the polar properties of the Bi 6s2 lone pair, which gives a first evidence of coupling between magnetic and ferroelectric order parameters.
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