Probing the complex magnetic structure of BaVS3 by resonant
magnetic X-ray scattering
P. Foury-Leylekian, J.-P. Pouget,
(LCPRM, Paris 6), Y. Joly (IN,
Switzerland)
Ph. Leininger (Max-Planck Intstitute, Germany), V. Ilakovac
Grenoble), E. Schierle (Bessy, Germany), H. Berger (EPFL,
In the physics of strongly correlated electronic systems exhibiting competing ground states, BaVS3
and related compounds have attracted considerable interest due to the interaction between itinerant
(dz2) and localized (et2g) electrons which involves a subtle interplay between charge, orbital and
spin degrees of freedom all together coupled with the lattice. This complex electronic structure
associated with a simple quasi-1D geometry built of Vanadium chains (see figure a) makes BaVS3 a
model compound for the study of competing orders in low-dimensional strongly correlated systems.
BaVS3 indeed presents a very rich phase diagram. Firstly, a metal-insulator transition which has
been associated with a Peierls 2KF charge density wave (CDW) instability of the dz2 electrons is
observed at 70K. Using anomalous X-ray scattering, we have previously shown that the CDW is also
accompanied by an ordering of the vanadium 3d orbitals (right part of figure a). Then at 30K, BaVS3
undergoes a magnetic transition. An important issue was thus to understand the origin of the
magnetism and to determine the role of the different vanadium orbitals in this transition.
In order to solve this complex magnetic ground state, we used resonant magnetic X-ray scattering
(RMXS) able to provide, on a small single crystal, information on the nature of the atoms bearing
the magnetism by choosing the X-ray absorption edge and to discriminate between the orbitals
involved in the magnetism using the polarization of the light. In the experiment performed at the
L2-3 edge of the vanadium, we have observed only a single magnetic reflexion. However the
measurement performed with different polarizations of the X-ray beam and an azimuthal angle
dependence analysis, coupled with the FDMNES code (able to calculate the anomalous intensity),
allows to determine the magnetic structure projected in the hexagonal (a,b) plane perpendicular to
the chain direction (figure b). This triply incommensurate magnetic structure, of the antiferromagnetic type, shows that the magnetisation is sustained by the e(t2g) orbitals and that the nodes
of the modulation are located on the non-magnetic dz² orbitals already paired at the Peierls
transition (figure b).
a.
Quasi-1D structure and orbital order of BaVS3
b. Magnetic structure (spin in red) obtained by RMXS
“Ground State of the Quasi-1D BaVS3 resolved by Resonant Magnetic X-ray Scattering” Ph. Leininger,
V. Ilakovac, Y. Joly, E. Schierle, E. Weschke, O. Bunau, H. Berger, J.-P. Pouget, and P. FouryLeylekian, Phys. Rev. Lett. 106, 167203 (2011)