Periodic Reporting for period 2 - INTERFAST (Gated INTERfaces for FAST information processing)
Período documentado: 2022-11-01 hasta 2024-10-31
The main objectives of the project aim at the achievement of:
Obj 1 Develop an innovative and disruptive technology able to control the Spin-Orbit Coupling in various Spintronic and Magnetic materials via the modulation of the chemical bonding at molecule-metal interfaces
(ACHIEVED, extensive and beyond the state of the art new knowledge, involves both experimental and theoretical sides, joint effort of Partners CNR, JSI, UNIVLEEDS, TUDO)
Obj 2 Define the fundamental rules enabling the SOC control via the hybridisation gating and the characteristic time, length and energy scales
(ACHIEVED via optical gating, partly achieved in Electric gating – beyond the state of the art in both cases)
Obj 3 Demonstrate the applicability and the competitiveness of this technology in both magnetic storage and magnetic processing
(ACHIEVED, but requires additional dissemination and exploitation efforts)
Obj 1 Develop an innovative and disruptive technology able to control the Spin-Orbit Coupling in various Spintronic and Magnetic materials via the modulation of the chemical bonding at molecule-metal interfaces
(ACHIEVED, extensive and beyond the state of the art new knowledge, involves both experimental and theoretical sides, joint effort of Partners CNR, JSI, UNIVLEEDS, TUDO)
Obj 2 Define the fundamental rules enabling the SOC control via the hybridisation gating and the characteristic time, length and energy scales
(ACHIEVED via optical gating, partly achieved in Electric gating – beyond the state of the art in both cases)
Obj 3 Demonstrate the applicability and the competitiveness of this technology in both magnetic storage and magnetic processing
(ACHIEVED, but requires additional dissemination and exploitation efforts)
1) Demonstrated the colossal magnetic hardening for the in-plane magnetization, induced in magnetic layers via the interfacial hybridisation with various molecular species
Demonstrated the enhancement of coercive fields by 100% at room temperature, for more than 2000% at 150K (Co/C60 and Co/Gaq3, Figure 1).
2) It was established that the hybridisation modifies the magnetic anisotropy deep inside the ferromagnetic layer, up to a few nm scales - effect demonstrated by Ferromagnetic nuclear resonance spectroscopy (Figure 2) and confirmed by multiple MOKE, SQUID, AMR and other measurements. (Partner CNR, Adv. Mater. Interfaces 2022, 2201394)
3) Electrical Gating
IINTERFAST pursued three gating approaches: direct voltage application in top-gate multilayered vertical devices (Partners CNR, UNIVLEEDS and Tyndall, Fig 3, left), electrolytic gating (Partner UNIVLEEDS) via ionic liquids (Fig 3, center) and, additionally, by forming a donor-acceptor bilayer near the interface (Partner UNIVLEEDS), producing a significant built-in voltage (Fig3, right).
4) Optical Gating
INTERFAST has realized the first successful optical gating of interfacial hybridization in Co/C60 systems, revealing a 60% modulation of GHz spin precession frequency using ultrashort laser pulses. Time-resolved magneto-optical Kerr effect (TR-MOKE) experiments further uncovered photoinduced transient modulation of out-of-plane magnetization in Pt/Co/H2-Pc heterostructures, achieving over 50% modulation at sub-nanosecond timescales.
The Figure 4 shows the sketch of the optical gating concept and the Figure 5 – the switching effect.
5) Radicals on ferromagnetic surfaces
We addressed (for the first time) the fabrication of a strongly hybridized radical(Blatter-pyr)/polycrystalline cobalt. Figure 6 (left) pyrene Blatter derivative, and (right) C 1s and N 1s core-level spectra of a thicker film (6.0 nm) compared to the interfacial layer (0.4 nm) spectra as indicated, together with their fit components, named as shown in the Blatter-pyr molecular structure (Ph stands for the phenyl ring).
6) A Hybrid Magneto-Optic Capacitive memory with ps writing time
Light exposure of FM/MOL/oxide devices results in short-circuit photocurrent and open circuit voltage. In a floating voltage, spin-dependent charge trapping at the fullerene/oxide interface leads to the formation of a magnetic interface as spins accumulate (Figure 7).
7) Low current density thermo-electric switching of compensated magnetic interfaces
Demonstrated a spin reorientation transition in conventional 3d ferromagnetic films with two interfaces (e.g. Pt/FM/MOL) (Figure 8). Near the switching temperature, the magnetisation easy axis can be reoriented with a small energy, either electrically with a current density ≲105 A/cm2, which is 1-2 orders of magnitude lower than in conventional metal, semiconducting or tunnel junction devices.
8) Strong unidirectional spin Hall magnetoresistance for spin-voltage conversion
The molecular layers on metal antiferromagnets manipulate the spin-polarised electronic structure, altering the spin canting, SOC and spin-voltage conversion as measured via magnetoresistance (MR) measurements when grown on a ferrimagnetic insulator (Figure 9). Notably, the effect in the AFM/MOL system is of the same magnitude as the conventional spin Hall MR and easily detected in MR measurements.
9) 3-terminal lateral devices
INTERFAST has brought to a new level the nano-technology of hybrid magnetic-molecular systems, delivering for the first time complex technologies combining UHV growth, EB lithography and 2D flakes manipulation. We have developed a new nanofabrication protocol which goes beyond the current state-of-the-art and which allows for the seamless integration of any kind of molecular layers on 2D materials.
10) Theory of magnetocrystalline anisotropy at hybrid molecule-metal interfaces.
A model theory, combined with first-principles numerical calculations, demonstrates that chemical bonding between molecular orbitals and the 3-orbitals of ferromagnetic transition metals at hybrid interfaces can significantly modify the MCA [Phys. Rev. Mater. 7, 064409 (2023)]. The molecular adsorption can be exploited to make a material, such as Co, magnetically harder or softer, as observed in experiments (CNR).
11) Advanced computational methods for spin transport
We developed a computational approach to study spin-orbit coupling (SOC)-driven transport effects from first principles using Density Functional Theory (DFT) combined with the Non-Equilibrium Green’s Functions (NEGF) framework [Phys. Rev. B 109, 195132 (2024)]. Specifically, we derived the fundamental equations required for the calculation of spin current and spin torque and implemented them in computational modules. [Phys. Rev. B 107, 174433 (2023) and Phys. Rev. B 109, 155141 (2024)].
12) Theory of the ferromagnetic spin glass
Advanced an innovative correlated random anisotropy model, predicting the emergence of a novel magnetic state called the “ferromagnetic glass state,” which has been observed experimentally in molecular films on Co (CNR). This effect is accompanied by a transition from the domains and domain walls characteristic of the ferromagnetic state to "melted domains" in the ferromagnetic glass state (Figure 10).
13) Prediction of novel charge-spin conversion phenomena
Predicted the emergence of new spin transport and conversion phenomena called “kinetic Rashba-Edelstein effect” and “interface spin Hall effect” due to interface disorder [Phys. Rev. Research 5, 033215 (2023)].
Demonstrated the enhancement of coercive fields by 100% at room temperature, for more than 2000% at 150K (Co/C60 and Co/Gaq3, Figure 1).
2) It was established that the hybridisation modifies the magnetic anisotropy deep inside the ferromagnetic layer, up to a few nm scales - effect demonstrated by Ferromagnetic nuclear resonance spectroscopy (Figure 2) and confirmed by multiple MOKE, SQUID, AMR and other measurements. (Partner CNR, Adv. Mater. Interfaces 2022, 2201394)
3) Electrical Gating
IINTERFAST pursued three gating approaches: direct voltage application in top-gate multilayered vertical devices (Partners CNR, UNIVLEEDS and Tyndall, Fig 3, left), electrolytic gating (Partner UNIVLEEDS) via ionic liquids (Fig 3, center) and, additionally, by forming a donor-acceptor bilayer near the interface (Partner UNIVLEEDS), producing a significant built-in voltage (Fig3, right).
4) Optical Gating
INTERFAST has realized the first successful optical gating of interfacial hybridization in Co/C60 systems, revealing a 60% modulation of GHz spin precession frequency using ultrashort laser pulses. Time-resolved magneto-optical Kerr effect (TR-MOKE) experiments further uncovered photoinduced transient modulation of out-of-plane magnetization in Pt/Co/H2-Pc heterostructures, achieving over 50% modulation at sub-nanosecond timescales.
The Figure 4 shows the sketch of the optical gating concept and the Figure 5 – the switching effect.
5) Radicals on ferromagnetic surfaces
We addressed (for the first time) the fabrication of a strongly hybridized radical(Blatter-pyr)/polycrystalline cobalt. Figure 6 (left) pyrene Blatter derivative, and (right) C 1s and N 1s core-level spectra of a thicker film (6.0 nm) compared to the interfacial layer (0.4 nm) spectra as indicated, together with their fit components, named as shown in the Blatter-pyr molecular structure (Ph stands for the phenyl ring).
6) A Hybrid Magneto-Optic Capacitive memory with ps writing time
Light exposure of FM/MOL/oxide devices results in short-circuit photocurrent and open circuit voltage. In a floating voltage, spin-dependent charge trapping at the fullerene/oxide interface leads to the formation of a magnetic interface as spins accumulate (Figure 7).
7) Low current density thermo-electric switching of compensated magnetic interfaces
Demonstrated a spin reorientation transition in conventional 3d ferromagnetic films with two interfaces (e.g. Pt/FM/MOL) (Figure 8). Near the switching temperature, the magnetisation easy axis can be reoriented with a small energy, either electrically with a current density ≲105 A/cm2, which is 1-2 orders of magnitude lower than in conventional metal, semiconducting or tunnel junction devices.
8) Strong unidirectional spin Hall magnetoresistance for spin-voltage conversion
The molecular layers on metal antiferromagnets manipulate the spin-polarised electronic structure, altering the spin canting, SOC and spin-voltage conversion as measured via magnetoresistance (MR) measurements when grown on a ferrimagnetic insulator (Figure 9). Notably, the effect in the AFM/MOL system is of the same magnitude as the conventional spin Hall MR and easily detected in MR measurements.
9) 3-terminal lateral devices
INTERFAST has brought to a new level the nano-technology of hybrid magnetic-molecular systems, delivering for the first time complex technologies combining UHV growth, EB lithography and 2D flakes manipulation. We have developed a new nanofabrication protocol which goes beyond the current state-of-the-art and which allows for the seamless integration of any kind of molecular layers on 2D materials.
10) Theory of magnetocrystalline anisotropy at hybrid molecule-metal interfaces.
A model theory, combined with first-principles numerical calculations, demonstrates that chemical bonding between molecular orbitals and the 3-orbitals of ferromagnetic transition metals at hybrid interfaces can significantly modify the MCA [Phys. Rev. Mater. 7, 064409 (2023)]. The molecular adsorption can be exploited to make a material, such as Co, magnetically harder or softer, as observed in experiments (CNR).
11) Advanced computational methods for spin transport
We developed a computational approach to study spin-orbit coupling (SOC)-driven transport effects from first principles using Density Functional Theory (DFT) combined with the Non-Equilibrium Green’s Functions (NEGF) framework [Phys. Rev. B 109, 195132 (2024)]. Specifically, we derived the fundamental equations required for the calculation of spin current and spin torque and implemented them in computational modules. [Phys. Rev. B 107, 174433 (2023) and Phys. Rev. B 109, 155141 (2024)].
12) Theory of the ferromagnetic spin glass
Advanced an innovative correlated random anisotropy model, predicting the emergence of a novel magnetic state called the “ferromagnetic glass state,” which has been observed experimentally in molecular films on Co (CNR). This effect is accompanied by a transition from the domains and domain walls characteristic of the ferromagnetic state to "melted domains" in the ferromagnetic glass state (Figure 10).
13) Prediction of novel charge-spin conversion phenomena
Predicted the emergence of new spin transport and conversion phenomena called “kinetic Rashba-Edelstein effect” and “interface spin Hall effect” due to interface disorder [Phys. Rev. Research 5, 033215 (2023)].
Established a comprehensive knowledge for the description of the complex physics in hybrid FM/Mol systems
Explored for the first time the manipulation of spin order, dynamics and spin-voltage conversion in antiferromagnetic/molecular multilayers.
Developed the first magneto-optic capacitive memory using FM/Mol/oxide architectures, in which the information can be manipulated by either optical or voltage signals in the sub-ps to ps timescales.
INTERFAST has delved into the spin physics of FM/MOL interfaces and found universal effects in controlled environments with a wide range of molecular materials.
Fabricated for the first time three-terminal lateral devices combining metallic electrodes, molecular layers and 2D-dielectric flakes.
Explored for the first time the manipulation of spin order, dynamics and spin-voltage conversion in antiferromagnetic/molecular multilayers.
Developed the first magneto-optic capacitive memory using FM/Mol/oxide architectures, in which the information can be manipulated by either optical or voltage signals in the sub-ps to ps timescales.
INTERFAST has delved into the spin physics of FM/MOL interfaces and found universal effects in controlled environments with a wide range of molecular materials.
Fabricated for the first time three-terminal lateral devices combining metallic electrodes, molecular layers and 2D-dielectric flakes.