Origin of Electric Field Induced Magnetization in Multiferroic HoMnO$_{3}$

We have performed polarized and unpolarized small angle neutron scattering experiments on single crystals of HoMnO$_{3}$ and have found that an increase in magnetic scattering at low momentum transfers begins upon cooling through temperatures close to the spin reorientation transition at $T_{SR} \quad \approx $ 40 K. We attribute the increase to an uncompensated magnetization arising within antiferromagnetic domain walls. Polarized neutron scattering experiments performed while applying an electric field show that the field suppresses magnetic scattering below $T \quad \approx $ 50 K, indicating that the electric field affects the magnetization via the antiferromagnetic domain walls rather than through a change to the bulk magnetic order. http://arxiv.org/abs/0909.0198v1