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Gated INTERfaces for FAST information processing

Periodic Reporting for period 1 - INTERFAST (Gated INTERfaces for FAST information processing)

Reporting period: 2021-05-01 to 2022-10-31

INTERFAST aims to develop a novel technological platform for the voltage control of interfacial magnetism. The key idea is to modulate the hybridization at the interface between a magnetic material and an organic layer by applying the electrical gating (EG) EG is employed to induce additional carriers in the organic materials, either electrons or holes, and hence modify the chemical bonding at the interface. This shall allow to control the interfacial magnetism of a wide range of magnetic and supporting compounds, thus providing a universal platform, which is not specific to the rare magnets exhibiting massive voltage-control magneto-crystalline anisotropy coefficients. Finally, INTERFAST investigates the applicability of this technology to a range of key spintronic functions, encompassing voltage control of magnetisation reversal at fJ/bit energy cost, drastic reduction of the spin-orbit-torque switching currents, and ultrafast THz information processing in all-metallic spintronic devices aided by gateable hybridisation unit.

The main objectives of the project aim at the achievement of:
1) highly efficient voltage induced magnetization switching (GHz memories and sensing);
2) ultimate reduction of the switching currents in Spin-Orbit torque (SOT) devices (GHz operation);
3) GHz-THz-range information processing and sensing via the SOC control in three terminal devices.

The potential of the INTERFAST technology for the societal needs is extremely promising.
As first output, INTERFAST will deliver a number of new magnetic materials based on the technology of interfacing the state-of-the-art ferromagnetic films with molecular layers. The interfacial hybridization induces radically different properties, providing unavailable so far means to tailor on demand the magnetic properties, especially the magnetic anisotropy. The enormous choice of the molecular species potentially allow to tailor the magnetic properties to nearly any needed value of the magnetic anisotropy, both in plane and perpendicular to plane.
The second potential output is the modification by the same technology of the Spin-Orbit torque elements with the expected reduction of the employed switching energies. The third output will consist of the tailoring of the spin scattering strength in spin conducting layers, with the possibility not only to reduce and but also to enhance the spin polarization of currents.
Finally, the electrical gating is supposed to offer a low-energy root to control by external stimuli all the described above properties: magnetic anisotropy, SOT and spin polarization.
Importantly, the first and the second outputs are compatible with GHz operation for information processing and sensing, while the third output can be employed even in THz regime, with possibility to achieve the amplification of signals in a truly spin transistor operation mode.
The main results achieved in the first 18 months are:

1) Development of the interfacing technology based on the hybridization of 3d ferromagnetic metals with molecular layers. The previous state-of-the art unsystematic achievements were converted in a reproducible technology based on established protocols with application of a number of different molecules.

2) Breakthrough observation of the colossal enhancement of the magnetic anisotropy in some hybridized systems, with a two-fold enhancement of the coercive fields at room temperature and beyond an order of magnitude enhancement at 100 K.

3) Demonstration of the retention of the enhanced magnetic anisotropy at frequencies up to tens of GHz by resonant techniques and fast magneto-optics.

4) Achievement of a consistent data base of microscopic parameters of hybridized metal-molecule interfaces for a large number of molecules.

5) Development of a conceptually new phenomenological model allowing for the description of large and colossal enhancement of the magnetic anisotropy and other magnetic properties in the hybridized FM metal-molecule systems.

6) Detection of large changes in the SOC dependent spin scattering in heavy metals such as platinum and tantalum featuring a strong coupling with fullerenes

7) Development of protocols for a number of electrical gating units, compatible with the hybrid metal-molecular systems and able to achieve electric fields beyond 106 V/cm

7) Design and establishment of fabrication protocols for 3-terminal spin devices based on metallic layers and innovative 2D spin conducting with electrical gating units.

The achieved results are fully in line with the project time-scale and constitute a solid basis for exploitation efforts to be pursued in the second part of the project and beyond the project. The dissemination of most of the results was actively pursued on the scientific level (publications, conference presentations etc), in social media (Twitter and Facebook) and in printed media.
Considering the hybridization effects on the Magnetic Anisotropy (MA), INTERFAST has consolidated the random and unsystematic knowledge provided by previous communications (including those of the INTERFAST partners), putting the basis for the conversion of these observations and communications in a real technology.
INTERFAST moved well beyond the state of the art on the strength of the enhancement of MA, achieving in some systems values well beyond one order of magnitude.

The project has built strong theoretical basis for hybrid interface magnetic technology by combining detailed DFT microscopic calculations with a macroscopic phenomenological model, shedding conceptually new light on the modification of the magnetic parameters and providing means for the prediction and design of interfaces with on-purpose tailored magnetic properties.

INTERFAST revealed strong modifications of the SOC in heavy metals, developing thus additional roots for the control of Spin Orbit Torque based devices, with a potential for a strong decrease of the switching energies.

If successfully confirmed and further developed, these achievements have the potential for a considerable breakthrough in the areas of magnetic devices and spintronics, providing new device paradigms and moving towards considerable reductions of the switching energies combined with high frequency operation modes.