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Séminaire PLUM : jeudi 16 novembre 2023 à 14h00

Alain Pignolet (INRS – Centre Énergie Matériaux Télécommunications, Canada)

Titre : The Quest for New Room Temperature Multiferroic Nanomaterials


Institut Néel, Salle F418 (Erwin Bertaut)
Note that drinks will be offered at the end of the talk to continue the discussion. Please bring your own glass or mug


Multiferroics are a special class of smart materials that exhibit both ferroelectric and magnetic properties and have generated great interest for a variety of applications, ranging from spintronic devices to novel photovoltaic devices, and from cryogenic-free highly-sensitive magnetic sensors to innovative non-volatile memories. However, obtaining materials with ferroelectric and magnetic properties that are sufficiently strong and robust at or above room temperature for potential integration into novel devices remains elusive, in particular under the form of high-quality thin films, which is required for integrated devices. 

As a result, different strategies have been pursued in the quest for thin films of novel multiferroic materials with good multiferroic properties at room temperature. One such strategy is to grow films of one material known to be multiferroic, but with properties not quite suitable for applications in real devices, and to modify it to enhance its properties (e.g. to increase its Curie temperature or to improve its ferroelectric or magnetic properties). Another strategy is to engineer a composite material with one component being ferroelectric and a second component being magnetic at the temperature of operation. Yet another approach is to generate a polar structural distortion in a magnetic material inducing spontaneous polarization and pyroelectricity and possibly ferroelectricity.

Epitaxial thin films and nanostructures of the room temperature ferroelectric and ferrimagnetic Bi2FeCrO6 (BFCO) synthesized by pulsed laser deposition (PLD), as well as our current understanding of their properties, will be presented as an example of the first strategy. The second scheme will be exemplified by presenting PLD synthesized thin films of two material systems exhibiting spontaneous in-situ formation of a multiferroic nanocomposite, namely nanocomposite epitaxial films of (i) maghemite (gamma-Fe2O3)/BiFeO3 and (ii) of tetragonal tungsten bronze Ba2LnFeNb4O15 (TTB-Ln) / BaFe12O19 / LnNbO4 (Ln = Eu, Sm). The third approach will be illustrated by PLD-grown epitaxial thin films of the metastable epsilon phase of Fe2O3 and of ε-AlxFe2-xO3 stabilized by epitaxial strain. In addition to its potential multiferroic properties, epsilon-Fe2O3 also exhibits at room temperature a large magnetic anisotropy and a ferromagnetic resonance frequency in the absence of any magnetic field in the low THz range, which is of interest for short-range wireless communications and ultrafast computer non-volatile magnetic memories.

Furthermore, an original application of nanoparticles of ferroelectric BaTiO3 for wastewater treatment will also be presented, where a model pollutant is degraded by piezocatalysis when the polluted water is ultrasonicated. From this and to conclude, a fascinating multidisciplinary project will be presented, where the various properties of core/shell composite multiferroic nanoparticles are exploited to selectively enter only cancerous cells and subsequently induce their apoptosis without affecting the normal cells, paving the way for potential cancer treatment without the need of any toxic drug.

The organizing committee.