This Phd report shows several aspects of multiferroic and magnetoelectric properties and especially the effect of magnetic properties on dielectric and magnetoelectric behavior of two families of compounds : the manganese trisulfure phosphorus MnPS3 and the iron langasite.We also present in details the magnetic dynamical chirality properties of the compound Ba3NbFe3Si2O14 of the langasite family.Iron langasites show a non centrosymetric and a chiral crystal structure. The macroscopic magnetization measurements and neutron scattering experiments, including the use of polarized neutrons and polarization analysis, have allowed to enlighten a double magnetic chirality (helical and triangular). This chirality has a signature in the magnetic excitations and notably by non zero cross sections associated to dynamical antisymmetric correlations of spins. Those results are interpreted by spin-wave calculations in a linear approach. At last, different energy scales appear in the paramagnetic fluctuations with, in particular, magnetic fluctuations associated to antisymmetric correlations.The MnPS3 manganese trisulfure compound exhibits an antiferromagnetic order with an non zero macroscopic toroidization and a non zero non diagonal magnetoelectric coupling. This coupling has been enlightened by spherical neutron polarimetry experiment. We played with antiferromagnetic domains by cooling the sample through its Néel température under crossed magnetic and electric fields.
