The atomic and magnetic structure of iron phosphate glasses

Adrian C. Wright*, Roger N. Sinclair, Joanna L. Giles & Richard Haworth
J.J. Thomson Physical Laboratory, University of Reading
G. Kanishka Marasinghe
Department of Physics,University of North Dakota,
Delbert E. Day
Graduate Center for Materials Research, University of Missouri-Rolla,

Iron phosphate glasses, xFe2O3.(1-x)P2O5, are not only of potential commercial importance for the immobilisation of plutonium and other high-level nuclear wastes but are also of great scientific interest in that, at low temperatures, they exhibit short-range antiferromagnetic (speromagnetic) ordering(1). In a previous paper(2), the authors presented neutron diffraction data for three samples with compositions 0.3Fe2O3.0.7P2O5, and 0.4Fe2O3.0.6P2O5 and 0.44Fe2O3.0.56P2O5 . Neutron diffraction data have now been recorded using the D4c diffractometer at the Institut Laue-Langevin (ILL; Grenoble, France) for a fourth sample, 0.35Fe2O3.0.65P2O5, which corresponds to the minimum in a plot of mass density vs. the mole fraction, x, of Fe2O3. All four glasses undergo magnetic ordering at low temperatures, and neutron diffraction measurements have been performed, using the earlier D4b diffractometer at a longer wavelength, l , of 0.7 Å to extract the magnetic correlation function, DM(r), by making measurements above (~77 K) and below (~4 K) the magnetic ordering transition region. This yields information concerning the Fe-Fe distances and the nature of the magnetic ordering within the material. Conclusions are drawn not only with regard to the validity of various structural models for these glasses but also concerning the extent of the speromagnetic ordering, the network topology and the environment and spatial distribution of the various cations.

1. J.L. Shaw, A.C. Wright, R.N. Sinclair, G.K. Marasinghe, D. Holland, M.R. Lees & C.R. Scales, J. Non-Cryst. Solids 345&346 (2004), 245.
2. A.C. Wright, R.N. Sinclair, J.L. Shaw, R. Haworth, G.K. Marasinghe & D.E. Day, Eur. J. Glass Sci. Technol. B: Phys. Chem. Glasses 49 (2008), 1.