Electric-field control of spin waves at room temperature in multiferroic BiFeO$_{3}$

A particularly exciting prospect in the field of spintronics is to use the wave like excitations of a magnetic material as a means to transmit and process information. This technology named magnonics relies on the control of spin waves. The key goal of magnonics is to read/write non-volatile spin information with minimal energy consumption. Multiferroic materials have at least two coupled magnetic and ferroelectric orders leading to electrical control of magnetic effects and vice-versa. Multiferroic materials are thus potentially interesting as a medium for spin-wave-based information processing. Here we show that the spin wave excitations in BiFeO$_{3}$, a room temperature multiferroic can be controlled by an electric field at low power and in a non-volatile way. The present experiment clearly demonstrates spin waves can be tuned over 30{\%} of their frequencies, several orders of magnitude larger than with previous methods. The switch and the control of the polarization is used to manage this tuning.