Berlin 2012 – wissenschaftliches Programm
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KR: Fachgruppe Kristallographie
KR 4: Joint Session "Multiferroics III - Strain / New Routes towards Multiferroicity" (MA jointly with DF, DS, KR, TT)
KR 4.12: Vortrag
Dienstag, 27. März 2012, 12:30–12:45, EB 301
Crystal growth and scattering investigations of YFe2O4− δ — •Thomas Müller1, Joost de Groot1, Jörg Strempfer2, and Manuel Angst1 — 1Peter Grünberg Institut PGI and Jülich Centre for Neutron Science JCNS, JARA-FIT, Forschungszentrum Jülich GmbH, 52425 Jülich, Germany — 2Deutsches Elektronen-Synchrotron DESY, D-22607 Hamburg, Germany
LuFe2O4 is attracting attention as proposed multiferroic compound, but there is much less known about other isostructural rare-earth ferrites. We have grown single-crystals of YFe2O4−δ in a CO/CO2-atmosphere to tune δ. Optimized crystals exhibit a magnetic behaviour identical to highly stoichiometric powder samples, i.e. two hysteretic phase transitions at 228 K and 180 K upon cooling.
Corresponding to these phases single-crystal x-ray-diffraction shows 3D-charge-ordered states, partially not compatible with the phases observed by electron diffraction [1]. At least one additional transition below 160 K, not present in magnetisation, is found in x-ray-diffraction. On one sample we found reflections at (1/3,1/3,half-integer) at 10 K , identical to the superstructure reflections of LuFe2O4. Nevertheless sample differences, due to different δ, have to be reviewed.
We further searched for anisotropy by resonant x-ray diffraction and full polarization analysis on superstructure reflections at PETRA III-P09. As for LuFe2O4 no anisotropy is observed. Although YFe2O4 has the same structure as LuFe2O4, the phases between 100 K and 230 K are totally different, showing much more complex incommensurate ordering. [1] N. Ikeda et al. Ferroelectrics 272, 309 (2002)