Objective
Insulating magnetoelectric (ME) crystals allow the induction of electric polarization by means of a magnetic field and of a magnetization by means of an electric field. The effect was first predicted and measured successfully on antiferromagnetic Cr2O3. In high magnetic fields (pulsed and continuous) the ME effect has become a precious tool for studying a variety of physical properties of magnetically ordered and non-centrosymmetric paramagnetic phases, e.g. magnetic field induced phases and phase transitions (temperature-magnetic field phase diagrams) and the determination of the magnetic symmetry of phases at such high fields, an extremely important technique, since magnetic symmetry and structure determination by neutron diffraction in high magnetic fields is not yet possible.
In the framework of the project the following work will be done: magnetoelectric measurements of boracites, perovskites and phosphates in high magnetic fields at the MPI/CNRS Grenoble and up to 2 Tesla at the University of Geneva; polarized light microscopical studies and down to 8 K on the domain structure and phase transitions of own single crystal samples and such ones of the NIS participants; influence of an electric field on the staggered magnetization reversal in EEH-type ME crystals; optical properties of EH and EEH-type ME crystals in a magnetic field and spectroscopic investigation of the magnetically induced ferroelastic phase transitions in EEHH ME crystals; optical spectroscopy and search for magnetic field induced ferroelastic/ferroelectric phase transitions in EHH-type ME crystals; measurement of some tensorial relations between applied magnetic field and the electric polarization induced by the magnetic field in single crystal samples of Tb (MoO4)3, Gd2(MoO4)3 and TbGd(MoO4)3; investigation of optical properties of these substances between 4.2 and 300 K; ferroelectric monodomain BiFeO3 samples; Bi1-xRxFeO3 (R = rare earth), BiFe1-xCoxO3 and (Cr1-xFex)2O3 solid solutions; study of the structure and the polymorphism of the solid solutions between 4 and 890 K and of the ME interaction in static magnetic fields up to 1 Tesla; experimental and theoretical investigation of the nature of the spatially modulated spin structure in antiferromagnets Bi1-xRxFeO3 (R = La, Dy), Bi(Fe1-xCox)O3 and (Cr1-xFex)2 O3; the magnetic, magnetoelectric and magnetoelastic properties of these single crystals in high magnetic fields up to 30 Tesla and in the temperature range from 4.2 to 300 K.
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1211 Genève 4
Switzerland