CE24 - Micro et nanotechnologies pour le traitement de l’information et la communication

MagnetoelectrIc oxideS for SpIn-OrbitroNics – MISSION

MagnetoelectrIc oxideS for SpIn-OrbitroNics

The energy required for data manipulation and storage are major societal issues. The low-power manipulation of magnetization has become a fundamental challenge for future magnetic information memory and storage technologies. Spin Hall effect-based spin-orbit torque is currently the most promising way to tackle this challenge and has proven its relevance for MRAMs applications. However, there is still a need to further decrease the power consumption of this current-driven effect.

We plan to achieve this goal through the implementation of an electric field-driven magnetoelectric material in spin Hall effect-based spin-orbit torque architectures.

Inserting an electric field-driven magnetoelectric material (ME) in spin Hall effect (SHE)-based spin-orbit torque (SOT) architectures will yield a possibility to tune the SOT spin injection in the ME material via the application of a voltage and will allow lowering the charge current necessary for the magnetization reversal. Such an electric field-assisted manipulation will also result in shorter time-scale magnetization reversal than observed for current-induced phenomena and a deterministic field-free magnetization switching. This will be the first study of the active role that ME material can play in SOT phenomena, with great expectations in terms of energy savings. There are very few ME materials which can be operated at room temperature. In this project, we will use one of these rare materials, which also presents a net room temperature magnetization, the gallium ferrite Ga0.6Fe1.4O3. The project is interdisciplinary and will develop the scientific expertise necessary to fulfill the following objectives: materials development, lithography methods, devices design, and techniques adapted to study the SOT-switching assisted by ME towards applications for new spintronics based sensors and actuators with low power consumption. The innovation in this project resides in the first insertion of a multifunctional material in a spin Hall effect architecture, thus potentially adding new tools to this rising technology.

The atomic-scale control of the interface between the multifunctional oxide thin film and the strong spin-orbit coupling material is one of the challenges addressed by the project. It will be tackled by RHEED monitored pulsed laser deposition of gallium ferrite thin films, post chracterized by high resolution transmission electron microscopy. The project also includes the determination of the conditions of the workability of these newly conceived tools. Various benefits are expected to result from this investigation of high spin-orbit metal / magnetoelectric oxide interfaces, from progress in fundamental knowledge to application-related lowered energy consumption in SHE-based FM magnetization switching. The methods will be macroscopic magnetic characterization tools such as SQUID, microscopic ones such as XMCD. Finally the spin/charge interconversion of oxide/Pt heterostructrues will be characterized using Hall bar lithographied devices.

Important interfacial phenomena between the STO substrates and the GFO deposited thin films have been evidenced at the atomic scale. Their impact on the ferrimagnetic and ferroelectric properties of the deposited layer have been unveiled and the deposition conditions for the desired films have been optimized. It is now possible to grow GFO thin films, with a control of down to the fourth of a unit cell.
The magneto-transport of GFP/Pt patterned Hall bars have shown clear magneto-resistance effects. Some temperature-dependent measurements with various orientations of the applied magnetic field (in-plane, parallel, or perpendicular to the applied current, or out-of-plane) could discriminate between anisotropic magnetoresistance (AMR) and spin Hall magnetoresistance (SMR). The SMR value measured for the GFO/Pt heterostructures is about 2 .10-4 at 300 K and 4.5 .10-4 at 20 K. This is identical to what is observed in YIG/Pd heterostructures and only slightly less than what is observed YIG/Pt (4 .10-4 at 300 K and 6 .10-4 at 20 K).

We have demonstrated through an atomically resolved transmission electron microscope study that the interface between a SrTiO3 (STO) substrate and the gallium ferrite thin film deposited on it at high temperature was very different from expected, with great impact on the structural, electric, and magnetic properties of the film for low thicknesses. Ti cations have indeed been observed to migrate, up to 5 nm deep, into the deposited oxide film. This migration is due to the greediness of Ti for oxygen and is allowed by the high deposition temperature. This phenomenon had not been evidenced before, although it most probably pollutes all oxides depositions on STO and should be generally considered to explain odd properties of the films at very low thicknesses.
The demonstration of SMR in GFO/Pt heterostructure is also a major achievment. This SMR is of the same order of magnitude as the ones measured in classical oxide/Pt heterostructures.
We now work on the demonstration of the possibility ot control the spin/charge interconversion in these heterostructures through the magnetoelectric effect offered by GFO.

1. S. Homkar, D. Preziosi, X. Devaux, C. Bouillet, J. Nordlander, M. Trassin, F. Roulland, C. Lefèvre, G. Versini, S. Barre, C. Leuvrey, M. Lenertz, M. Fiebig, G. Pourroy, N. Viart, Phys. Rev. Mater. 2019, 3, 124416.
2. T. Fache, J.C. Rojas-Sanchez, L. Badie, S. Mangin, S. Petit-Watelot, Phys. Rev. B 2020, 102, 064425.

Energy and data manipulation and storage are undoubtedly major societal issues. The low-power manipulation of magnetization, preferably at ultra-short time scales, has become a fundamental challenge for future magnetic information memory and storage technologies.
Spin Hall effect (SHE)-based spin-orbit torque (SOT) is currently the most promising way to tackle this challenge, and has proven its relevance for Magnetic Random Access Memories (MRAM) applications. However there is still a need to further decrease the power consumption of this current-driven effect.
We plan to achieve this goal through the implementation of an electric field-driven magnetoelectric (ME) material in SHE-based SOT architectures. This will yield a possibility to tune the SOT spin injection in the ME material via the application of a voltage and will allow lowering the charge current necessary for the magnetization reversal. Such an electric field-assisted manipulation will also result in shorter time-scale magnetization reversal than observed for current-induced phenomena and truly field-free magnetization switching. This will be the first study of the active role that can play a ME material in SOT phenomena, with great expectations in terms of energy savings.
There are very few ME materials which can be operated at room temperature. In this project, we will use one of these rare materials, which also presents a net room temperature magnetization, the gallium ferrite Ga0.6Fe1.4O3. The project is interdisciplinary and will develop the scientific expertise necessary to fulfill the following objectives: materials development, lithography methods, devices design and techniques adapted to study the SOT-switching assisted by ME towards applications for new spintronics based sensors and actuators with low power consumption.

The innovation in this project resides in the first insertion of a multifunctional material in a spin Hall effect architecture, thus potentially adding new tools to this rising technology. The atomic scale control of the interface between the multifunctional oxide thin film and the strong spin-orbit coupling material is one of the challenges addressed by the project. It also includes the determination of the conditions of workability of these newly conceived tools. Various benefits are expected to result from this investigation of high spin orbit metal / magnetoelectric oxide interfaces, from progress in fundamental knowledge to application-related lowered energy consumption in SHE-based FM magnetization switching.

Project coordinator

Madame Nathalie Viart (IPCMS)

The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.

Partner

IPCMS IPCMS
IJL Institut Jean Lamour

Help of the ANR 444,213 euros
Beginning and duration of the scientific project: - 36 Months

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