Element-specific magnetic order and competing interactions in Gd0.8Eu0.2S

We report on the determination of element-specific magnetic order for a Gd0 .8Eu0.2S mixed crystal by means of X-ray resonance exchange scattering. For the first time, a different temperature dependence of the sublattice magne tization of two lanthanide ions was observed. With model calculations we we re able to reproduce the measured temperature dependence of the reduced sub lattice magnetization. We can show that competing magnetic interactions lea d to the observed effects and can reveal the frustration mechanism.