Magnetoelectric Molecular Materials – MEMORi

The general purpose consists in the chemical design and investigations of the physical properties of original ME molecular materials. To realize this study, the proposal is organized into three interconnected Tasks:
Task n°1 intends to design chiral molecular complexes based on lanthanide ions and various Schiff-base ligands.. Our objective will be to achieve a systematic analysis of the parameters that affect the ferroelectric properties (nature Ln3+ ions, ligands, space groups, solvents) and in fine the ME coupling. Three different shaping methods of the materials will be investigated for the electrical characterization (Task 2),: 1) single-crystals; 2) thin films obtained by spin or dip-coating on ITO substrates; 3) molecular ceramics obtained by using the Cool-Spark Plasma Sintering (SPS, Partner 2) method allowing the sintering of thermodynamically fragile materials at reasonable temperature (200-400°C) to allow for insightful dielectric and ME characterizations.
Task n°2 will involve the study of the individual properties of the resulting molecular architectures. The magnetic and photo luminescent properties will be studied by the scientific coordinator (Partner 1). Screening of the ferroelectric measurements at the macroscopic scale will be investigated by two parallel approaches: on single-crystals and thin-films by Partner 1 and on molecular ceramics by Partner 2. Following this, all the most promising systems, regardless of the shaping, will be investigated in details by Partner 2 by measuring the dielectric properties, pyroelectric currents and investigating the piezoelectric properties.
Task n°3 will be dedicated to the investigation of the ME coupling on the best performing materials obtained in Task 2 by measuring the magnetic field dependence of dielectric and pyroelectric properties (Partner 2).

From a synthetic point of view, new chiral Schiff base ligands have been prepared for the design of novel magnetoelectric complexes. A new polar complex NiYb has nevertheless been obtained and characterized and will be the subject of detailed study.
The large-scale synthesis of a ZnYb reference ferroelectric complex was developed for shaping studies at ICMB as well as for understanding magneto-electric coupling (task 3).
The first Cool-SPS shaping tests were conducted at the ICMCB. They established the range of experimental conditions tolerable by the ZnYb complex. This showed good stability under Cool-SPS conditions (high vacuum, uniaxial pressure, application of electrical power, etc.). These initial works suggest that the conditions favorable for the sintering of this complex by Cool-SPS are in the temperature and pressure range supported by this material. These first SPS experiments are encouraging for future dielectric studies, but it remains necessary to determine the optimal sintering conditions, ensuring both good densification and good reproducibility.

The first ferroelectric measurements have shown promising results, particularly in the form of large single crystals. Additional work is now necessary to determine in detail the parameters affecting the ferroelectric measurements (size of single crystals, crystal orientation, etc.) and thus to propose a reliable methodology.
The study of dielectric properties on molecular ceramics will begin soon (ICMCB). The recent availability of new cells dedicated to the measurement of dielectric properties, developed independently of the MEMORI project, will make it possible to carry out preliminary measurements on ceramics. These measurements will guide the selection of advanced dielectric measurement conditions (low temperature, under magnetic field, magnetoelectric measurements, etc.)

En cours

Magnetoelectric (ME) materials combine magnetization (M) and polarization (P) through cross-couplings M(E) and P(H) and provide starting materials for developing high-density data storage, spintronics and low consumption devices owing to the interplay between both properties. Modifying M or P through either a magnetic or electric field may reduce the needed energy in non-volatile memories various devices. Yet, designing such multifunctional materials is far to be straightforward owing to the phenomenological origin of both magnetism and ferroelectricity which tends to exclude each other. In addition, one of the key questions for future development concerns the mutual coupling between both properties in order to be able to control one property by the other.


While the wide majority of ME materials belong to metal oxides, we propose to investigate an original family of ME molecular materials which have been poorly investigated for such purpose.
MEMORI is a multidisciplinary fundamental research project at the crossroad of different disciplines involving coordination and materials chemistries and physical studies with the aims to design and investigate new and original ME molecular materials exhibiting strong coupling between both properties. Up to now, the in-depth study of the electric properties of molecular materials appears quite difficult since dense samples (large single-crystals) are required to obtain reliable data. This requires engineering and developing new methodologies that are specifically dedicated to such fragile materials. Therefore, our proposal intends to bring important breakthroughs for investing the ferroelectric properties in such materials, understanding the parameters affecting ferroelectricity up to the investigation of the synergy between magnetism and ferroelectricity.
We expect to give the proof that such molecular materials could be used to conceive systems in which the information is stored as electrically detectable but controllable by magnetism. In a more general context, we would like to demonstrate that molecular materials can be competitive in terms of properties such as ferroelectricity, with metal oxides, allowing them to be finally considered as potential candidates for future applications.

The MEMORi proposal aims to design multifunctional ME molecular materials exhibiting strong ME coupling with two main objectives:
i) The chemical design of molecular ferroelectric paramagnets of high chemical robustness based on the association between lanthanide ions and chiral Schiff base ligands. Efforts will be given to engineer systems exhibiting a high dielectric Tc or decomposition temperature with various shaping methods (single-crystals, molecular ceramics and thin films) that could eventually find subsequent applications. A specific stress will be given to develop methodologies to efficiently characterize the electric properties in order to comprehend the origins of the ferroelectricity in molecular complexes.
ii) Experimentally evidence the synergy and coupling between the magnetic and dielectric properties. Namely we expect to give the proof-of-concept that such strong interplay could be used to conceive device applications where stored-information is electrically detectable but controllable by magnetism and vice versa. Such results would represent a major breakthrough in the field of molecular and more generally in solid-state materials.
This proposal relies on strong expertises between two partners (ICGM and ICMCB) involving coordination and materials chemistry, molecular magnetism and ferroelectricity. This proposal goes all the way from the synthesis of the targeted molecular materials, their shaping in various forms, the fine understanding of their ferroelectric properties by various approaches, to the study of the ME coupling.