On the effect of short-range magnetic ordering on electron energy-loss spectra in spinels

McComb, D. W.; Craven, A. J.; Chioncel, L.; Lichtenstein, A. I.; Docherty, F. T.

On the effect of short-range magnetic ordering on electron energy-loss spectra in spinels

Authors

Description

The energy-loss near-edge structure (ELNES) at the oxygen $K$ edge in two $AB_2O_4$ spinels (A=Mg, B=Al,Cr) is reported. In $MgAl_2O_4$ the experimental data is successfully modelled within the LDA framework. In the case of $MgCr_2O_4$ spin-polarisation, in the form of antiferromagnetic ordering on the Cr sub-lattice, must be included despite the fact that the measurements were performed at approximately 30 times above $T_N$. 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.
10 pages, 3 figures