Crystal symmetry lowering in chiral multiferroic Ba 3 TaFe 3 Si 2 O 14 observed by x-ray magnetic scattering
Abstract
Chiral multiferroic langasites have attracted attention due to their doubly chiral magnetic ground state within
an enantiomorphic crystal. We report on a detailed resonant soft x-ray diffraction study of the multiferroic
Ba3TaFe3Si2O14 at the FeL2,3 and oxygenK edges. BelowTN (≈27K)we observe the satellite reflections (0,0,τ ),
(0,0,2τ ), (0,0,3τ ), and (0,0,1 − 3τ) where τ ≈ 0.140 ± 0.001. The dependence of the scattering intensity on
x-ray polarization and azimuthal angle indicate that the odd harmonics are dominated by the out-of-plane (ˆc
axis) magnetic dipole while the (0,0,2τ ) originates from the electron density distortions accompanying magnetic
order.We observe dissimilar energy dependencies of the diffraction intensity of the purelymagnetic odd-harmonic
satellites at the Fe L3 edge. Utilizing first-principles calculations, we show that this is a consequence of the loss
of threefold crystal symmetry in the multiferroic phase.
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