Element-specific magnetic long- and short-range order and competing interactions in Gd _x Eu _{1 - x} S

Abstract:

We report on an investigation of the magnetic properties of Gd _x Eu _{1 - x} S mixed crystals with compositions in the range of 0.6 < x < 1. For the two samples Gd _0.8 Eu _0.2 S and Gd _0.73 Eu _0.27 S a long-range antiferromagnetic order was observed at low temperatures. Element-specific measurements exhibited a different temperature dependence of the reduced sublattice magnetisation of the two magnetic species. A model calculation and Monte Carlo simulations revealed that the different temperature dependence is due to frustration effects. These frustration effects lead to a breakdown of the long-range order for higher europium contents. For the Gd _0.67 Eu _0.33 S-sample we were able to observe a short-range antiferromagnetic order with correlation lengths of a few 10Å with X-ray resonance exchange scattering.