JCJC SIMI 4 - JCJC - SIMI 4 - Physique des milieux condensés et dilués

DYnimical Magneto-electrical coupling in Muliferroics by Optical Spectroscopy – DYMMOS

Submission summary

The present project dwells on the recent surge of interest in a family of very attractive materials in which both ferroelectric and magnetic orders are present. These materials, known as multiferroics, have attracted much attention worldwide because they display larger magnetoelectrical effects as compared with previously studied materials. Multiferroics open the possibility of tuning the polarization direction with a magnetic field and/or the change the magnetization direction via an applied voltage. Multiferroic materials are therefore prime candidates for the manipulation of spin states via electric fields and the tuning of dielectric properties via magnetic fields, both very desirable for spintronic applications. 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 just as optical waves are manipulated in electro-optics and photonics technologies. One of the project goals is to electrically control spin waves in thin films for application in new magnonic devices providing a framework to realize low power and non-volatile magnetoelectric devices. The project is focused on the study of a wide range of multiferroic materials, all oxides, by means of inelastic light scattering (or Raman scattering). Because of its ability to probe both magnetic (magnon) and lattice (phonons) collective excitations, Raman scattering is uniquely suited to study the interplay of magnetic and lattice (or ferroelectric) degrees freedom. This ability was first demonstrated by the seminal Raman studies on ferroelectrics in the 70’s which were instrumental in establishing the soft mode approach to ferroelectric phase transitions. In the particular case of mutiferroics, while most of the studies, up to recently, have been focused on the static magnetoelectric effects, we specifically aim at probing the dynamical coupling between spin and lattice degrees of freedom in various class of multiferroic materials. This coupling remains largely unexplored today despite recent theoretical and experimental hints that fundamentally novel collective excitations, such as electric dipole active magnons or electromagnons. These hybrid excitations might be unique to materials with both ferroelectric and magnetic orders. In this proposal, the potential of Raman scattering to yield crucial informations on the microscopic mechanisms of magnetoelectric effects will be used under various external parameters such as magnetic field, electric field and pressure. The intend of these external parameters will be to tune both magnetic and ferroelectric orders and simultaneously study their impact on lattice and spin degrees of freedom in search for novel dynamical effects. The materials studied will range from high temperature multiferroics such as BiFeO3 to low temperature magnetic ferroelectrics like TbMnO3, DyMn2O5 and DyFeMnO5. Their magnetic and ferroelectric phase diagram as a function of magnetic and electric fields, pressure and temperature will be explored. The potentially unifying concept of electromagnon excitation will be addressed in light of up to date theories of magneto-electrical effects in multiferroic materials.

Project coordination

Maximilien CAZAYOUS (Laboratoire Matériaux et Phénomènes Quantiques) – maximilien.cazayous@univ-paris-diderot.fr

The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.

Partner

MPQ Laboratoire Matériaux et Phénomènes Quantiques

Help of the ANR 211,000 euros
Beginning and duration of the scientific project: December 2012 - 36 Months

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