A new chiral phase of BiFeO3 evidenced from resonant x-ray Bragg diffraction

Workshop on Resonant Elastic X-ray Scattering in Condensed Matter 2013

Rodriguez-Fernandez, A.^1 ; Lovesey, S.W.^2,3 ; Collins, S.P.^3 ; Nisbet, G.^3 ; Blanco, J.A.^1

Physics Department, University of Oviedo, C/ Calvo Sotelo s/n, Oviedo, Spain^1

ISIS Facility, STFC, Oxfordshire OX11 0QX, United Kingdom^2

Diamond Light Source Ltd, Oxfordshire OX11 0DE, United Kingdom^3

关键词: Antiferromagnetics;    Azimuthal angle;    Bragg diffraction;    Chiral structures;    Ferroelectric phase;    Forbidden reflections;    Magnetic dipole;    Multiferroic materials;   

Others  :  https://iopscience.iop.org/article/10.1088/1742-6596/519/1/012012/pdf
DOI  :  10.1088/1742-6596/519/1/012012

来源: IOP

【 摘 要 】

Results that support a new chiral phase in the only multiferroic material known above room temperature have been obtained by a resonant x-ray Bragg diffraction experiment, with the incoming x-ray beam tuned near the Fe K-edge (7.1135 keV), performed in its ferroelectric phase. The R3c forbidden reflection (0,0,9)H was studied as a function of the rotation of the crystal about the Bragg wavector in both phases, paramagnetic (700 K) and antiferromagnetic (300 K). The data gathered is consistent with a chiral structure formed by a circular cycloid propagating along (1,1,0)H. Templeton and Templeton (T&T) scattering at 700 K is attributed in part to charge-like quadrupoles absent in a standard model of a cycloid in which a material vector generates all electronic states of the resonant ion. Extensive sets of azimuthal-angle data are used to infer values of three atomic multipoles in a satisfactory minimal model of the iron electronic structure, with a quadrupole (E1-E1 event) and a hexadecapole (E2-E2 event) contributing T&T scattering, plus a magnetic dipole (E1-E1).