  We show that strong electromagnon peaks can be found in absorption spectra of
non-collinear magnets exhibiting a linear magnetoelectric effect. The
frequencies of these peaks coincide with the frequencies of antiferromagnetic
resonances and the ratio of the spectral weights of the electromagnon and
antiferromagnetic resonance is related to the ratio of the static
magnetoelectric constant and magnetic susceptibility. Using a Kagome lattice
antiferromagnet as an example, we show that frustration of spin ordering gives
rise to magnetoelastic instabilities at strong spin-lattice coupling, which
transform a non-collinear magnetoelectric spin state into a collinear
multiferroic state with a spontaneous electric polarization and magnetization.
The Kagome lattice antiferromagnet also shows a ferroelectric
incommensurate-spiral phase, where polarization is induced by the exchange
striction mechanism.
