Spinorbitronics exploits the spin-orbit coupling in materials, allowing the manipulation of magnetic information with currents rather than magnetic fields. This approach drastically reduces energy consumption and paves the way for the development of low energy-consumption devices, that could complement CMOS both for memories and logic circuits. Recently, two spin-orbit devices have been proposed, the magneto-electric spin-orbit (MESO) device and the ferroelectric spin-orbit (FESO) device. Both rely on the spin-charge interconversion for the read operation and use different switching mechanisms for the write operation. In order to develop such spinorbitronic devices, the spin-charge interconversion output signal needs to be optimised. For this, recently discovered materials are at the core of research, in particular topological insulators, ferroelectric Rashba semiconductors and Rashba interfaces, thanks to their interesting surface or interface properties. This thesis focuses on the spin-charge interconversion in bidimensional electron gases (2DEGs) at the surface of perovskite oxides. Beyond a wide range of intriguing properties, from magnetism to superconductivity, the 2DEG allows a large spin-charge interconversion, which can be modulated both in sign and amplitude by an electric-control. This offers new perspectives for low energy-consumption applications. To gain more insights into the non-volatile behavior of the 2DEG at some metal/SrTiO3 (STO) interfaces, the first part of this thesis is dedicated to the exploration of the 2DEG transport properties. In this system, we demonstrate that the non-volatile electric-control is induced by charge trapping. In addition, we used a scanning transmission electron microscopy to investigate the atomic structure of the metal/STO interface and complementary measurements suggest a strong localisation of electrons in the structure. This work enables the development of a 2DEG-based Flash memory, with an on/off ratio of 105, a retention time exceeding 5×105 s and an endurance over 106 cycles. In a second part, based on the charge-trapping-induced non-volatile behavior of the 2DEG conductivity, we demonstrate the non-volatile electric-control of the spin-orbit torques generated by the charge-to-spin conversion in a ferromagnet/metal/STO system. It shows a modulation in amplitude and in sign of the damping-like torque with the applied electric-field. This is an important milestone for the development of reconfigurable SOT-MRAMs. A complementary study of the spin-orbit torques is performed using the spin-torque ferromagnetic resonance, showing an optimised charge-to-spin conversion for 1 nm of Ta, reactive metal deposited to create the 2DEG. Finally, we successfully develop a spin-orbit read-out device with a large spin-charge interconversion output signal of 2 Ω. This demonstrates the potential of the 2DEG at the metal/STO for the development of the read-out of the MESO and FESO devices.

Plus d'information :https://www.spintec.fr/phd-defense-spin-charge-interconversion-in-oxide-based-2d-electron-gases-for-low-energy-consumption-nanodevices/
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Pour suivre la soutenance ​​​en visioconférence : https://univ-grenoble-alpes-fr.zoom.us/j/3241920232​

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