Abstract
We have studied the magnetic eld dependence of far-infrared active magnetic modes in a single
ferroelectric domain BiFeO3 crystal at low temperature. The modes soften close to the critical eld
of 18.8T along the [001] (pseudocubic) axis, where the cycloidal structure changes to the homogeneous
canted antiferromagnetic state and a new strong mode with linear eld dependence appears
that persists at least up to 31 T. A microscopic model that includes two Dzyaloshinskii-Moriya interactions
and easy-axis anisotropy describes closely both the zero- eld spectroscopic modes as well
as their splitting and evolution in a magnetic eld. The good agreement of theory with experiment
suggests that the proposed model provides the foundation for future technological applications of
this multiferroic material.
