Despite their immense interest in the data storage, materials science and fundamental physics, scope and applications of multiferroic compounds to date are hindered by the weakness of the polarization generated by magneto-electric coupling (ME). In this project, we propose an original approach for designing efficient multiferroic inorganic compounds associated with strong ME effects due to their unique topologies. Indeed, LOVE-ME relies on our recent discovery of inorganic compounds built on Low- Dimensional Ferromagnetic units. Dealing with isolated 1D, 2D and pseudo 3D (blocks) topologies carrying large collinear or canted macrospins, and their alignment under an external field they form the ideal playground for giant ME properties, compared to standard type I/type II multiferroics (weak ME coupling / low polarization generated via antiferromagnetic structures of cycloidal type). Our preliminary results on selected systems already suggest giant magneto-polarization. Quantification / optimization / systematic analysis of ME coupling will allow us to update the concepts behind these giants effects and to identify the key physico-chemical parameters. After the implementation of these key parameters in new low-FM D compounds dedicated, we will access to a new generation of high-performance multiferroic compounds.
Indeed, our multi-step strategy includes all stages, from the Design and modeling, Elaboration, Crystal Growth, fine Structural and Physical Characterization of relevant low-D ME, until the measurements and analysis of the intrinsic ME exchanges and responsible symmetries. The establishment of the ideal chemical/structural/magnetic context for giant ME is a prerequisite for the elaboration of optimal multiferroics. This identification will lift both the scientific and technological obstacles to the implementation of multiferroic in the devices.
Concerning the already available samples, source of inspiration, we have recently designed inorganic compounds with remarkable magnetic properties, i.e. rare examples of low-D ferromagnetic compounds with incommensurate structures, large magnetic periodicities, inorganic single-chain-magnets, and 2D-Ising FM. Their structural topologies associated with strong spin-orbit couplings (SOC) and original spin-flip-like transitions give all pre-requisites for enhanced magneto-electric (ME) couplings and electric polarization of magnetic origin (type II multiferroics). These compounds can be considered as intermediate between “molecular magnets” and “standard” inorganic magnets, and then correspond to a novel class of “full-inorganic molecular magnets”, a new paradigm in ME materials. We aim to modify and optimize the already available compounds and to produce new-inspired ones by structural design. For the conception of further compounds within an extended series, we have to handle individual magnetic units and well adapted spacers, according to incremental magnetic dimensionalities. In pseudo-3D phases ( i.e. isolated blocks), room-temperature magnetic orderings are expected, a challenging step of industrial relevance.
In fine, a new generation of advanced multiferroic materials with enhanced ME couplings will be achieved, using a rational methodology. It follows that LOVE-ME covers a broad range of concepts and techniques, including the Design and production of single-crystalline and polycrystalline materials the evidence of exacerbated ME effects across metamagnetic transitions (alignment of the microspins), their understanding by symmetry analysis and the identification of the key-ME parameters.
Monsieur Olivier Mentré (Unité de Catalyse et de Chimie du Solide)
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.
UCCS Unité de Catalyse et de Chimie du Solide
CRISMAT laboratoire de cristallographie et de science des matériaux
INEEL INSTITUT NEEL - CNRS
Help of the ANR 478,261 euros
Beginning and duration of the scientific project: September 2016 - 48 Months