Ground State of the Quasi-1D Compound ${\mathrm{BaVS}}_3$ Resolved by Resonant Magnetic X-Ray Scattering

Resonant magnetic x-ray scattering near the vanadium $L_{2,3}$-absorption edges has been used to investigate the low temperature magnetic structure of high quality ${\mathrm{BaVS}}_3$ single crystals. Below $T_N=31\mathrm{K}$, the strong resonance revealed a triple-incommensurate magnetic ordering at the wave vector $(0.2260.226\xi )$ in hexagonal notation, with $\xi =0.033$. The azimuthal-angle dependence of the scattering signal and time-dependent density functional theory simulations indicate an antiferromagnetic order within the $ab$ plane with the spins polarized along $a$ in the monoclinic structure.

Figure 1

Energy dependence of the magnetic reflection at $(0.2260.226\xi )$ measured at 10 K. The solid line is the result of the FDMNES code calculation (see text). The inset shows the $\mathrm{V}\mathrm{\text{−}}{L}_{2,3}$ x-ray absorption spectra (XAS) recorded in total fluorescence yield mode (dots) and compared with FDMNES simulation (solid line).

Figure 2

Rocking curve of the magnetic signal measured at $\Psi =90°$ (upper panel) and at $\Psi =0°$ (lower panel). The gray (blue) lines correspond to a fit with a Gaussian profile. The inset shows the temperature dependence of the $(0.2260.2260.033)$ magnetic reflection measured at 10 K with 516.5 eV photon energy.

Figure 3

Azimuthal-angle ($\Psi$) dependence of the ratio of resonant-peak intensities measured with $\sigma$ and $\pi$ incident polarized beam (black triangles). The blue dashed line corresponds to the FDMNES simulation when the spins are polarized along $a_{Im}$ (see text). The schematic illustrates the definition of $\Psi$ and shows the scattering geometry at $\Psi =0°$.

Figure 4

Magnetic structure of ${\mathrm{BaVS}}_3$ in the monoclinic (black) and hexagonal [gray (blue)] lattice deduced from combined RMXS measurements and ab initio calculations.