Ondes acoustiques de surface pour les dispositifs magnoniques

Ondes acoustiques de surface pour les dispositifs magnoniques

Director(s): Laura Thevenard et Pauline Rovillain
Funding:
Description :
Start: 2024
End: 2027
PhD Sudent :
Team(s): Acoustique et optique pour les nanosciences et le quantiqueNanostructures : élaboration, effets quantiques et magnétisme
Teams' Page of thesis : Acoustique et optique pour les nanosciences et le quantiqueNanostructures : élaboration, effets quantiques et magnétisme
Thesis status: Experimental et Thèse proposée

Keywords:  Magnetism, magnonic, spintronic, magneto-acoustic

Scientific description: A substantial portion of today’s magnetism research community dedicates its efforts to achieving highly integrated, rapid, and energy-efficient information and communication technologies that can operate at room temperature. In this context, Spin Waves (SW) emerge as promising contenders. SW, often referred to as magnons, represent collective excitations of electron spins within magnetic materials, traversing the spin lattice to convey information (see Fig.1). At INSP, our primary interest lies in instigating SWs within nanostructures through external stress and acoustic means. Indeed, the advent of spintronic devices that manipulate magnetization through strain rather than conventional inductive methods (like antennas) holds the potential for substantial reductions in energy dissipation.

In our pioneering approach, SWs find their ignition in the propagation of surface acoustic waves (SAW), a well-established technology already employed in contemporary sensors, filters, and microwave circuitry. Recently, our research group demonstrated that SAWs, initiated through interdigitated transducers (IDT), can effectively generate SWs in Fe epitaxied on GaAs [1,2]. These SWs typically span frequencies ranging from 800 MHz to 2 GHz, meticulously selected to align with the resonance frequencies of SWs. Notably, voltage-controlled IDTs replace conventional inductive antennas for SW emission in devices composed of Fe dots coupled to a SW waveguide (see Fig. 2).

During this thesis, the final  objective will be to be able to externally and independently control SW emission in different waveguides by exciting the magnetic resonance of Fe pads, whilst keeping the waveguide insensitive to the magnetoelastic interaction, thanks to nitrogen implantation.

For this we will employ TR-MOKE (Time Resolved-MagnetoOptical Effect), a potent method for scrutinizing magnetization dynamics [3,4] to evidence a  magnetization precession in Fe induced by acoustic waves. After observing the acoustically-induced propagation of SWs within the waveguide, we will endeavor to regulate SW emission by applying an external voltage to a piezoelectric layer situated atop the Fe. This piezoelectric layer will induce deformations in the Fe pads, thereby altering their magnetic properties, which we will assess through acoustic measurements and TR-MOKE.

The student’s involvement will progress through several stages, commencing with device fabrication and the comprehensive examination of its magnetic characteristics. Subsequently, the student will delve into magnetoacoustics measurements and participate in TR-MOKE experiments. This multifaceted experience will encompass hands-on exposure to clean room protocols, optics, and RF electronics equipment essential for conducting magnetoacoustics experiments. Ultimately, the student will actively contribute to the development of a phenomenological model aimed at elucidating the observed phenomena.

 

[1] Duquesne et al., Phys. Rev. Appl.  12, 024042 (2019) [2] Rovillain et al., Phys. Rev. Appl.  18, 064043 (2022) [3] Kuszewski et al., Phys. Rev. Appl. 10, 034036 (2018) [4] Kraimia et al., Phys. Rev. B 101, 144425 (2020).