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 Neel temperat ure a magnetically disordered region exists at the surface, and is separate d from the magnetically ordered bulk by a diffuse magnetic interface. The w idth of the magnetic interface is temperature dependent, and appears to div erge as the sample temperature approaches the bulk Neel temperature. In con trast to the bulk, which exhibits a discontinuous magnetic ordering transit ion, the surface layers order continuously. These results are shown to be q ualitatively consistent with the theory of surface induced disorder.