Ground State of the Quasi-1D bvs resolved by Resonant Magnetic X-ray Scattering

Resonant-magnetic x-ray scattering (RMXS) near the vanadium $L_{2,3}$-absorption edges has been used to investigate the low temperature magnetic structure of high quality bvs single crystals. Below $T_N$ = 31 K, the strong resonance revealed a triple-incommensurate magnetic ordering at wave vector (0.226 0.226 $xi$) in the hexagonal notation, with $xi$ = 0.033. The simulations of the experimental RMXS spectra with a time-dependent density functional theory indicate an antiferromagnetic order with the spins polarized along $a$ in the monoclinic structure.

Electronic structure, magnetic and dielectric properties of the edge-sharing copper-oxide chain compound NaCu$_{2}$O$_{2}$

We report an experimental study of co, a Mott insulator containing chains of edge-sharing CuO$_4$ plaquettes, by polarized x-ray absorption spectroscopy (XAS), resonant magnetic x-ray scattering (RMXS), magnetic susceptibility, and pyroelectric current measurements. The XAS data show that the valence holes reside exclusively on the Cu$^{2+}$ sites within the copper-oxide spin chains and populate a $d$-orbital polarized within the CuO$_4$ plaquettes. The RMXS measurements confirm the presence of incommensurate magnetic order below a Neel temperature of $T_N = 11.5$ K, which was previously inferred from neutron powder diffraction and nuclear magnetic resonance data. In conjunction with the magnetic susceptibility and XAS data, they also demonstrate a new orbital selection rule for RMXS that is of general relevance for magnetic structure determinations by this technique. Dielectric property measurements reveal the absence of significant ferroelectric polarization below $T_N$, which is in striking contrast to corresponding observations on the isostructural compound lco. The results are discussed in the context of current theories of multiferroicity.