PhD defense – Emma Aoustin

On Thursday, December 17, at 15 h (TRT Auditorium), Emma Aoustin will defend her PhD thesis titled “Molecular spintronics : From redox molecular monolayers to switchable magnetic tunnel junctions”, supervised by Richard Mattana and Pierre Seneor.

Jury members:

Stéphane Lenfant, Research Director at IEMN Lille, Reviewer
Simon Tricard, Research Director at LPCNO Toulouse, Reviewer
Amandine Bellec, Research Director at MPQ Paris Cité, Examiner
Céline Dablemont,  Professor at ISMO Orsay, Examiner

Abstract: 

Spintronics has revolutionized modern electronics by introducing new possibilities for data storage and magnetic sensing technologies. The integration of organic molecules into these junctions has given rise to molecular spintronics, which offers numerous advantages, such as variety, limitless functional possibilities, low cost, and flexibility.

This thesis work focuses on the study of self-assembled monolayers (SAMs) of redox-active molecules belonging to the polyoxometalate (POM) family, with particular focus on their transport properties and integration into magnetic tunnel junctions (MTJs). POMs are known for their remarkable redox properties, as they can reversibly accept and donate multiple electrons. The aim of this work is to investigate how POM switching affects the spin-dependent transport properties of spintronic devices. The fundamental concepts of spintronics and molecular spintronics will first be introduced. Following a presentation of the studied molecules, the procedure for functionalizing a ferromagnetic surface with POMs will be described, along with the characterization techniques used to analyze the resulting monolayer. Local electrical characterization will then be performed using CT-AFM, demonstrating that the molecules can be electrically addressed. Reversible switching of molecular conductance has been achieved through both electrical stimulation and UV illumination. In the second part of this work, the molecules will be integrated into complete spintronic devices: NiFe/POM/Co. Transport measurements confirm that conduction through the molecules occurs via tunneling. Under an applied magnetic field, the devices exhibit a clear tunneling magnetoresistance (TMR) signal. Finally, in situ switching of the molecular redox state in the junction modifies its resistance and can influence the TMR signal. These results demonstrate the potential of redox-active molecules for the development of multifunctional and switchable spintronic devices.