Resonant x-ray scattering studies of the magnetic structure near the surface of an antiferromagnet

Resonant x-ray magnetic scattering is used to study magnetic order near the (001) surface of the antiferromagnetic oxide UO2 for temperatures between 10 and 35 K. It is found that for temperatures below the bulk Néel temperature a magnetically disordered region exists at the surface, and is separated from the magnetically ordered bulk by a diffuse magnetic interface. The width of the magnetic interface is temperature dependent, and appears to diverge as the sample temperature approaches the bulk Néel temperature. In contrast to the bulk, which exhibits a discontinuous magnetic ordering transition, the surface layers order continuously. These results are shown to be qualitatively consistent with the theory of surface induced disorder.