  Electric manipulation of magnetic properties is a key problem of materials
research. To fulfil the requirements of modern electronics, these processes
must be shifted to high frequencies. In multiferroic materials this may be
achieved by electric and magnetic control of their fundamental excitations.
Here we identify magnetic vibrations in multiferroic iron-borates which are
simultaneously sensitive to external electric and magnetic fields. Nearly 100%
modulation of the terahertz radiation in an external field is demonstrated for
SmFe3(BO3)4. High sensitivity can be explained by a modification of the spin
orientation which controls the excitation conditions in multiferroic borates.
These experiments demonstrate the possibility to alter terahertz magnetic
properties of materials independently by external electric and magnetic fields.

Materials Science