  We calculate the temperature-dependent magnetoelectric response of Cr2O3 from
first principles. The form of the dominant magnetoelectric coupling is
determined using symmetry arguments, its strength is found using ab initio
methods, and the temperature dependence of the response is obtained from Monte
Carlo simulations. The quantitative agreement of our results with experiment
shows that the strong temperature dependence of the magnetoelectric effect in
Cr2O3 results from non-relativistic exchange interactions and spin
fluctuations.
