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Observation and manipulation of antiferromagnetic distributions in magneto-electric multiferroics

L'INRS est fier de recevoir le chercheur Jean-Yves Chauleau dans le cadre d'un séminaire intitulé « Observation and manipulation of antiferromagnetic distributions in magneto-electric multiferroics » le 24 novembre 2022.

24 novembre 2022

De 11 h 00 à 12 h 30

Centre Énergie Matériaux Télécommunications

Salle Tudor-Johnston (salle 2024)

1650, boul. Lionel-Boulet

Varennes (Québec)  J3X 1S2

Ouvert à la communauté scientifique

Gratuit

Résumé

Antiferromagnets (AF) are currently in the limelight thanks to recent breakthroughs demonstrating the efficient effect of spin currents in interacting with the AF order parameter [1,2]. So far, due to the lack of net magnetization, controlling AF distributions has been rather challenging. Current-induced AF control also opens therefore new perspectives in Terahertz magnetization dynamics. On the materials side, antiferromagnets represent the large majority of magnetic materials and some of them show several simultaneous coupled ordered phases. They are commonly called ‘multiferroics’. As a result, when the AF order is coupled to a net
polarization, it may be controlled by applying a voltage. Multiferroic materials [3] are the focus of an intense research effort due to the significant technological interest of multifunctional materials as well as the rich fundamental physics lying in the coupling of various order parameters. Among all multiferroics, BiFeO3 (BFO) is a material of choice because its two ordering temperatures (ferroelectric FE and AF) are well above room temperature. In addition, a large magnetoelectric coupling has been demonstrated in single crystals as well as in thin films. One downside of multiferroics is that these FE/AF textures can be rather challenging to assess. Second harmonic generation has proven to be a powerful and elegant way to image complex multiferroïc textures and to unentangle the different contributions at play [4].

In this presentation, I will present a study demonstrating the possibility to use second harmonic generation (SHG) to access the micron sized distribution of
AF domain (Figure 1) in a multiferroic thin film [5]. Subsequently, we will study their ultrafast dynamics by assessing the time evolution of the multiferroic texture when subjected to an intense femtosecond light pulse. Eventually we will discuss how they could be efficiently manipulated by the internally optically rectified sub-picosecond electric fields which could open the door to an all-optical terahertz control the AF order, independently of the electric polarization, but still using the magnetoelectric effect. Another interesting consequence of this large magneto-electric coupling is the stabilization a spin cycloid. As topology is now playing a major role in spintronics, tailoring chiral antiferromagnetic features is therefore of significant relevance and in a last part I will discuss the
observation and manipulation of these chiral objects in thin BiFeO3 epitaxial layers [6,7].

References
[1] T. Jungwirth, X. Marti, P. Wadley and J. Wunderlich Nature Nanotech. 11, 231 (2016) [2] P. Wadley
and al. Science 351, 587 (2016) [3] N. Spalding and M. Fiebig, Science, 309, 391 (2005) [4] M. Fiebig &
al., Nature, 419, 818, (2002) [5] J.-Y. Chauleau & al., Nature Materials, 16, 803, (2017) [6] I. Gross et
al., Nature, 549, 252, (2017) [7] J.-Y. Chauleau & al., Nature Materials, 19, 386, (2020)

Biographie

Jean-Yves Chauleau is currently a permanent researcher at CEA Saclay in the “Service de Physique de l’Etat Condensé” (SPEC). His specialization in spintronics and magnetization dynamics has begun during his PhD at the Laboratoire de Physique des Solides (Orsay), supervised by Dr. André Thiaville where he has studied spin current-induced dynamics in magnetic nanostructure. He graduated in 2010. Then always tackling spintronics issues, he have gained expertise in time-resolved magneto-optics during a 3-year postdoctoral stay in the group of Prof Christian Back (Regensburg) where, he had the opportunity to develop and oversee a project centered around the key parameters of spintronics, before bringing he skills in optics and ultrafast dynamics at CEA/SPEC in the nanomagnetism and oxides group (LNO) to setup a new activity, first as a postdoctoral fellow, focused on optical second harmonic generation to study the physics multiferroic textures in oxides. During several postdoctoral stays in Paris-Saclay landscape, he has also gained expertise in the physics of ferroic oxides, for example by studying complex topological orders using synchrotron-based techniques such as X-ray resonant scatterings. Nowadays, he is developing and leading a research activity in the nanomagnetism & oxides group at CEA/SPEC focused on timeresolved and nonlinear optics to tackle various issues of the physics of oxides.