Magnetic x-ray-scattering study of uranium arsenide

Abstract

The resonant magnetic x-ray scattering in UAs has been measured from 3.4 to 5.0 keV through the ${\mathit{M}}_{\mathrm{III}}$, ${\mathit{M}}_{\mathrm{IV}}$, and ${\mathit{M}}_{\mathrm{V}}$ absorption edges. The data are fit by three dipole oscillators that add coherently. The polarization dependence of nonresonant magnetic scattering was measured at 7.6 keV in the type-IA 2q phase below T=63 K. The ratio of the (0,1/2,2${)}^{\mathrm{\ensuremath{\sigma}}\mathrm{\ensuremath{-}}\mathrm{\ensuremath{\pi}}}$ magnetic reflection to the (0,0,2${)}^{\mathrm{\ensuremath{\sigma}}\mathrm{\ensuremath{-}}\mathrm{\ensuremath{\sigma}}}$ charge reflection is 1\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}9}$, and the ratio calculated assuming the free-ion values of L=6 and S=3/2 is 1.04\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}9}$. This is a direct measurement of the strong orbital contribution to the magnetic moment in UAs. In the type-IA phase a tetragonal lattice distortion with c/a=1.0002 and a (003${)}^{\mathrm{\ensuremath{\sigma}}\mathrm{\ensuremath{-}}\mathrm{\ensuremath{\sigma}}}$ charge peak associated with a charge modulation at 2\ensuremath{\tau}, where \ensuremath{\tau} is the modulation wave vector of the magnetic structure, were observed.