Headlines 2007

Multi-ferroïcs are exceptional materials whose fundamental state is both magnetic and ferro-electric [1]. Moreover, in such materials, magnetism and ferroelectricity maintains close links: as for example the manganese oxide YMnO₃ [2], can see its magnetization modified by the action of an electric field, or its electric polarization by the action of a magnetic field (magnetoelectric effect). Muli-ferroïcity is a complex problem in physics of condensed matter; it also represents an important stake for the applications, and for example for “technologies for the information and health” developed at the CEA (development of new concepts of memorizing the information or spin electronics).

The last research on these materials tends to show that the coupling between magnetism and ferro-electricity occurs via important deformations of the crystal lattice. It is known for example that in the case of the compound YMnO₃, the transition (T_N = 72K) towards the magnetic phase (and thus multi-ferroïc) is the seat of magnetostrictive effects that reveals the strong coupling between atomic displacements, magnetic ferroelectricity and moments.