Speaker
Description
Multiferroic materials exhibiting coupled magnetic and electric orderings are intensely
studied due to an interest in both their fundamental properties and potential applications based
on the magnetoelectric coupling. In general, magnons are collective spin excitations of
various types. In multiferroics, the electric component of the electromagnetic radiation can
excite magnons via the dynamic magnetoelectric coupling. These excitations are then called
electromagnons; they can be difficult to distinguish from classical magnons. One possible
method consists in comparing terahertz or infrared spectra with Raman spectra. In fact, the
electromagnons, unlike magnons, must follow the same selection rules as polar
phonons—they must be active in both kinds of spectra.
In this presentation, we will illustrate our approach by the study of nickel tellurides [1,2,3].
Indeed, a colossal magnetoelectric coupling has been found in Ni 3 TeO 6 . For the first time, we
managed to synthetise its isostructural compounds by substitution of Ni with Mn or Co. Low-
temperature spectra revealed electromagnons sensitive to magnetic field, which proves the
multiferroic character of the compounds.
