Effect of short-range magnetic ordering on electron energy-loss spectra in spinels

The energy-loss near-edge structure (ELNES) at the oxygen K edge in two AB/sub 2/O/sub 4/ spinels (A=Mg, B=Al, Cr) is reported. In MgAl/sub 2/O/sub 4/ the experimental data are successfully modelled within the local density approximation framework. In the case of MgCr/sub 2/O/sub 4/ spin polarization, in the form of antiferromagnetic ordering on the Cr sublattice, must be included despite the fact that the measurements were performed at approximately 30 times above T/sub N/. A model in which dynamic short-range antiferromagnetic ordering is present at room temperature is proposed to explain the results of the experiments and calculations.