The Atomic and Magnetic Structure and Dynamics of Iron Phosphate Glasses


Iron phosphate (Fe2O3-P2O5) glasses with a high Fe2O3 content are particularly interesting in that they exhibit short range antiferromagnetic (speromagnetic) ordering at low temperatures. Neutron scattering techniques have been employed to investigate the atomic and magnetic structure and dynamics of four iron phosphate glasses, as a function of their nominal composition between 30 and 44 mol% Fe2O3, and the data are compared with earlier structural models in which the Fe3+ cations are either tetrahedrally or 6-fold co-ordinated by oxygen. Fe2+ cations are also found to be present in 6-fold (trigonal-prismatic and/or octahedral) co-ordination. Neutron magnetic diffraction experiments yield information concerning the Fe-Fe distances and confirm the speromagnetic nature of the magnetic ordering, whilst a measurement of the magnetic inelastic scattering from vitreous 40Fe2O3.60P2O5 reveals the presence of dispersive magnetic excitations centred on the first magnetic diffraction peak at 0·82 å-1. It is concluded that all four glasses have structures that are much more complicated than the above models would suggest and include Fe3+ cations in both tetrahedral and octahedral co-ordination. A comparison with the structure of the corresponding crystalline phases suggests that the glasses are nanoheterogeneous, with FePO4-like regions (alternating FeØ4- and PØ4+ corner sharing tetrahedra) and those having a more typical phosphate chain structure incorporating Fe2+/Fe3+ network modifying cations.


Materials Science and Engineering

Keywords and Phrases

Antiferromagnetics; Atomic and magnetic structures; Corner-sharing tetrahedra; Crystalline phasis; Information concerning; Iron phosphate glass; Iron phosphates; Low temperatures; Magnetic diffraction; Magnetic excitations; Neutron magnetic diffraction; Neutron scattering techniques; Nominal composition; Phosphate chain; Structural models

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Article - Journal

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