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

TL;DR

This paper investigates how short-range magnetic ordering influences the oxygen K-edge electron energy-loss spectra in spinel materials, revealing that magnetic effects persist well above the Néel temperature and affect spectral features.

Contribution

It introduces a model incorporating dynamic short-range antiferromagnetic ordering to explain ELNES spectra in spinels at room temperature, highlighting magnetic effects beyond long-range order.

Findings

Magnetic ordering affects ELNES spectra in spinels.

Short-range antiferromagnetic correlations exist at room temperature.

Model successfully explains experimental spectra.

Abstract

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.