J. Rouquette
University of Montpellier, France
Title: Interplay between H-bonding and charge ordering in Fe3 (PO4)2(OH)2 barbosalite
Biography
Biography: J. Rouquette
Abstract
Charge Ordering (CO) in transition metal oxides is an important parameter for obtaining original magnetic and/or electric properties. That was largely shown within the framework of the studies on colossal magneto-resistance in manganese perovskites and it again seems to be at the origin of the ferroelectricity in CaMn7O12 or LuFe2O4. The mixed valence of iron in the system is a particular motivation in view of the long lasting research on the understanding of the effects of pressure on charge order/magnetic order in iron compounds such as the LuFe2O4 new charge ordered state and the pressure dependence of its magnetic order. Here we focus on Fe2+Fe3+2(PO4)2(OH)2 barbosalite single crystal, an hydroxyphosphate of iron which exhibits a mixed valence state. High pressure behavior of barbosalite was successfully characterized based on single crystal X-ray diffraction, Raman and infrared spectroscopies. Fe2+Fe3+2(PO4)2(OH)2 presents two phase transition at close to 3 and 8 GPa respectively which are clearly governed by an interplay between H-bonding and electron delocalization. Moreover the temperature reaction Fe2+Fe3+2(PO4)2(OH)2Ò Fe3+3(PO4)2(OOH).
