Berlin 2012 – scientific programme

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DS: Fachverband Dünne Schichten

DS 17: Multiferroics III: Strain / New routes towards multiferroicity (jointly with MA, DF, KR, TT)

DS 17.12: Talk

Tuesday, March 27, 2012, 12:30–12:45, EB 301

Crystal growth and scattering investigations of YFe₂O_{4− 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 YFe₂O_4−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)