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Master 2 Internship : Tuning the spin waves dynamic in multiferroics by uniaxial strain

Pr. Maximilien Cazayous,

publié le , mis à jour le

The project dwells on the recent surge of interest in a family of very attractive oxyde materials in which both ferroelectric and magnetic orders are present. These materials, known as multiferroics, have attracted much attention worldwide because they open the possibility of tuning the polarization direction with a magnetic field and/or the change the magnetization direction via an applied voltage. Multiferroic materials are therefore prime candidates for the manipulation of spin states via electric fields and the tuning of dielectric properties via magnetic fields, both very desirable for applications.

Bismuth ferrite (BiFeO3) is the only multiferroïc showing very high polarization at room temperature and a strong ferroelastic response under strain. This compound is amazing because it has a spiral spin structure coupled to the ferroelectricity. Using optical spectroscopies (Raman in our lab, time resolved acoustic at INSP, SU and synchrotron radiations at Soleil), we have investigated spins excitations, phonon modes (lattice vibrations) and hybrid excitations (electromagnon) under different conditions (pressure, uniaxial strain, low temperature, under electric and magnetic field).
Our work has given major contributions in the field [1-3] to undestand the multiferroic properties and to propose applications.

The aims of this experimental project is to set up a unuxial strain experiment to opticaly measure the behavior of the spin and lattice excitations as a function of the strain on BiFeO3. We are expecting a stong modification of the magnetic and ferroelectric response under this uniaxial strain.
This work is based on national collaborations with UMR φ Thales, Synchrotron Soleil, CEA Saclay and international partners : university of Tokyo, MIT, …

This subject is a premilary work for a thesis in our team.

[1] Driving spin excitations by hydrostatic pressure in BiFeO3 single crystals, J. Buhot et al., Phys. Rev. Lett. 115, 267204 (2015).
[2] Colossal electromagnon excitation in the non-cycloidal phase of TbMnO3 under pressure, I. Aupiais et al, NPJ Quantum Materials 3, 60 (2018).
[3] Elastic properties assessment in the multiferroic BiFeO3 by pump and probe method, P. Hemme, et al., Appl. Phys. Lett. 118, 062902 (2021) [Editor’s Pick].