Stabilization of Spin and Charge Ordering in Stoichiometric YbFe2O4

摘要

We report a wide-range reciprocal space observation with neutron diffraction in an iron vacancy controlled YbFe2O4 crystal, which is proposed as a prototype of electronic ferroelectrics arising from iron charge ordering. The increase of the charge ordering transition temperature and the disappearance of spin competitive transition were discovered in this stoichiometric crystal. We suppose that the lower ionic deficiency of this crystal enhances the development of spin and charge order coherence length, and consequently, the intrinsic nature of spin and charge ordering of YbFe2O4 could be detected. The experiment was performed with a two-dimensional neutron detector, and all super-lattice spots and its modulations above magnetic ordering temperature T-N = 245 K are successfully explained with six domains of a monoclinic charge-order super-lattice cell. A rather extended two dimensional (2D) spin correlation above T-N was identified with polarized He-3 neutron spin filter and we found a clear indication of a coupling between the 2D spin correlation and charge ordering between T-N and 300 K, at which a new lattice distortion phase may set in.