| 1. |
- Behera, Nilamani, et al.
(författare)
-
Ultra-Low Current 10 nm Spin Hall Nano-Oscillators
- 2024
-
Ingår i: Advanced Materials. - 0935-9648 .- 1521-4095. ; 36:5
-
Tidskriftsartikel (refereegranskat)abstract
- Nano-constriction based spin Hall nano-oscillators (SHNOs) are at the forefront of spintronics research for emerging technological applications, such as oscillator-based neuromorphic computing and Ising Machines. However, their miniaturization to the sub-50 nm width regime results in poor scaling of the threshold current. Here, it shows that current shunting through the Si substrate is the origin of this problem and studies how different seed layers can mitigate it. It finds that an ultra-thin Al2O3 seed layer and SiN (200 nm) coated p-Si substrates provide the best improvement, enabling us to scale down the SHNO width to a truly nanoscopic dimension of 10 nm, operating at threshold currents below 30 (Formula presented.) A. In addition, the combination of electrical insulation and high thermal conductivity of the Al2O3 seed will offer the best conditions for large SHNO arrays, avoiding any significant temperature gradients within the array. The state-of-the-art ultra-low operational current SHNOs hence pave an energy-efficient route to scale oscillator-based computing to large dynamical neural networks of linear chains or 2Darrays.
|
|
| 2. |
- Behera, Nilamani, et al.
(författare)
-
Ultra-low-current Spin Hall Nano-oscillators
- 2023
-
Ingår i: 2023 IEEE International Magnetic Conference - Short Papers, INTERMAG Short Papers 2023 - Proceedings. - 9798350338362
-
Konferensbidrag (refereegranskat)abstract
- We report on the magnetodynamic properties and the magnetization auto-oscillations of ultra-low current 20 nm width nano-constriction spin Hall nano-oscillators (SHNOs) fabricated on different substrates and seed layers. Combining an optimized W88Ta12 alloy, low damping CoFeB, and a moderate perpendicular magnetic anisotropy, we push the threshold current down to 35 μA in the best devices. The best overall magnetodynamic properties and lowest threshold currents are obtained when using a 3 nm thick AlOx seed layer in between the high-resistance Si substrate and the W88Ta12 layer.
|
|
| 3. |
- Chaurasiya, Avinash Kumar, et al.
(författare)
-
Direct observation of unusual interfacial Dzyaloshinskii-Moriya interaction in graphene/NiFe/Ta heterostructures
- 2019
-
Ingår i: Physical Review B. - 2469-9950 .- 2469-9969. ; 99:3, s. 1-6
-
Tidskriftsartikel (refereegranskat)abstract
- Graphene/ferromagnet interface promises a plethora of new science and technology. The interfacial Dzyaloshinskii-Moriya interaction (iDMI) is essential for stabilizing chiral spin textures, which are important for future spintronic devices. Here, we report direct observation of iDMI in graphene/Ni80Fe20/Ta heterostructures from nonreciprocity in spin-wave dispersion using Brillouin light-scattering technique. Linear scaling of iDMI with the inverse of Ni80Fe20 thicknesses suggests primarily interfacial origin of iDMI. Both iDMI and spinmixing conductance increase with the increase in defect density of graphene obtained by varying argon pressure during sputter deposition of Ni80Fe20. This suggests that the observed iDMI originates from defect-induced extrinsic spin-orbit coupling at the interface. The direct observation of iDMI at graphene/ferromagnet interface without perpendicular magnetic anisotropy opens a route in designing thin-film heterostructures based on two-dimensional materials for controlling chiral spin structure such as skyrmions and bubbles, and magnetic domain-wall-based storage and memory devices.
|
|
| 4. |
- Gupta, Pankhuri, et al.
(författare)
-
Generation of out-of-plane polarized spin current in (permalloy, Cu)/EuS interfaces
- 2024
-
Ingår i: PHYSICAL REVIEW B. - 2469-9950 .- 2469-9969. ; 109:6
-
Tidskriftsartikel (refereegranskat)abstract
- The generation of out-of-plane polarized spin current is crucial for efficiently manipulating perpendicularly magnetized systems used in high-density magnetic recording. Here, we demonstrate the generation of out-of-plane polarized spin current at room temperature using an insulator, EuS. By employing angleresolved spin-torque ferromagnetic resonance, we find a large unconventional out-of-plane torque conductivity, sigma zDL = -0.13 x 105( h over bar /2e) (S2 m)-1 in the Py(= Ni81Fe19)/EuS bilayer, which is comparable to the conventional in-plane dampinglike torque conductivity, sigma yDL. Additionally, a giant in-plane fieldlike torque (sigma zFL) with a magnitude of 27 times larger than that of the conventional out-of-plane fieldlike torque (sigma yFL) is also observed in the Py/EuS bilayer. The unconventional torques due to the out-of-plane polarized spin current (sigma zDL and sigma zFL) persist even by inserting a 10-nm-thick Cu layer between Py and EuS. Our findings demonstrate that the unconventional torques in these systems originate from the interfaces through spin swapping and/or spin-orbit precession mechanisms.
|
|
| 5. |
- Mudgal, Richa, et al.
(författare)
-
Magnetic-Proximity-Induced Efficient Charge-to-Spin Conversion in Large-Area PtSe2/Ni80Fe20 Heterostructures
- 2023
-
Ingår i: NANO LETTERS. - 1530-6984 .- 1530-6992. ; 23:24, s. 11925-11931
-
Tidskriftsartikel (refereegranskat)abstract
- As a topological Dirac semimetal with controllable spin-orbit coupling and conductivity, PtSe2, a transition-metal dichalcogenide, is a promising material for several applications, from optoelectrics to sensors. However, its potential for spintronics applications has yet to be explored. In this work, we demonstrate that the PtSe2/Ni80Fe20 heterostructure can generate large damping-like current-induced spin-orbit torques (SOT), despite the absence of spin-splitting in bulk PtSe2. The efficiency of charge-to-spin conversion is found to be -0.1 +/- 0.02 nm(-1) in PtSe2/Ni80Fe20, which is 3 times that of the control sample, Ni80Fe20/Pt. Our band structure calculations show that the SOT due to PtSe2 arises from an unexpectedly large spin splitting in the interfacial region of PtSe2 introduced by the proximity magnetic field of the Ni80Fe20 layer. Our results open up the possibilities of using large-area PtSe2 for energy-efficient nanoscale devices by utilizing proximity-induced SOT.
|
|
| 6. |
- Bainsla, Lakhan, et al.
(författare)
-
Spin-orbit torques in Co2MnGa magnetic Weyl semimetal thin films
- 2023
-
Ingår i: 2023 IEEE International Magnetic Conference - Short Papers, INTERMAG Short Papers 2023 - Proceedings. - 9798350338362
-
Konferensbidrag (refereegranskat)abstract
- Due to the nontrivial topology in their electronic band structure, topological quantum materials are known to exhibit unconventional surface states and anomalous transport properties. In the present study, the ferromagnetic Heusler alloy Co2MnGa, which breaks time-reversal symmetry, is studied to estimate its spin-orbit torque efficiency. Epitaxial thin films with high structural ordering are obtained, which show very high values of anomalous Hall conductivity. A spin-orbit torque efficiency of 0.13±0.01 is obtained in a 20 nm Co2MnGa film. The present results open the possibility to use these exotic materials in spintronic devices and beyond.
|
|
| 7. |
- Bainsla, Lakhan, et al.
(författare)
-
Ultrathin Ferrimagnetic GdFeCo Films with Low Damping
- 2022
-
Ingår i: Advanced Functional Materials. - : Wiley. - 1616-301X .- 1616-3028. ; 32:23, s. 2111693-
-
Tidskriftsartikel (refereegranskat)abstract
- Ferromagnetic materials dominate as the magnetically active element in spintronic devices, but come with drawbacks such as large stray fields and low operational frequencies. Compensated ferrimagnets provide an alternative as they combine the ultrafast magnetization dynamics of antiferromagnets with a ferromagnet-like spin-orbit-torque behavior. However, to use ferrimagnets in spintronic devices their advantageous properties must be retained also in ultrathin films (t < 10 nm). In this study, ferrimagnetic Gdx(Fe87.5Co12.5)1−x thin films in the thickness range t = 2–20 nm are grown on high resistance Si(100) substrates and studied using broadband ferromagnetic resonance measurements at room temperature. By tuning their stoichiometry, a nearly compensated behavior is observed in 2 nm Gdx(Fe87.5Co12.5)1−x ultrathin films for the first time, with an effective magnetization of (Formula presented.) = 0.02 T and a low effective Gilbert damping constant of α = 0.0078, comparable to the lowest values reported so far in 30 nm films. These results show great promise for the development of ultrafast and energy efficient ferrimagnetic spintronic devices.
|
|
| 8. |
- Bangar, H., et al.
(författare)
-
Large Spin Hall Conductivity in Epitaxial Thin Films of Kagome Antiferromagnet Mn3Sn at Room Temperature
- 2022
-
Ingår i: Advanced Quantum Technologies. - : Wiley. - 2511-9044. ; 6:1
-
Tidskriftsartikel (refereegranskat)abstract
- Mn3Sn is a non-collinear antiferromagnetic quantum material that exhibits a magnetic Weyl semimetallic state and has great potential for efficient memory devices. High-quality epitaxial c-plane Mn3Sn thin films have been grown on a sapphire substrate using a Ru seed layer. Using spin pumping induced inverse spin Hall effect measurements on c-plane epitaxial Mn3Sn/Ni80Fe20, spin-diffusion length (lambda(Mn3Sn)), and spin Hall conductivity (sigma(SH)) of Mn3Sn thin films are measured: lambda(Mn3Sn) = 0.42 +/- 0.04 nm and sigma(SH) = -702 h/e Omega(-1)cm(-1). While lambda(Mn3Sn) is consistent with earlier studies, sigma(SH) is an order of magnitude higher and of the opposite sign. The behavior is explained on the basis of excess Mn, which shifts the Fermi level in these films, leading to the observed behavior. These findings demonstrate a technique for engineering sigma(SH) of Mn3Sn films by employing Mn composition for functional spintronic devices.
|
|
| 9. |
- Bangar, H., et al.
(författare)
-
Large Spin-To-Charge Conversion at the Two-Dimensional Interface of Transition-Metal Dichalcogenides and Permalloy
- 2022
-
Ingår i: ACS Applied Materials & Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 14:36, s. 41598-41604
-
Tidskriftsartikel (refereegranskat)abstract
- Spin-to-charge conversion is an essential requirement for the implementation of spintronic devices. Recently, monolayers (MLs) of semiconducting transition-metal dichalcogenides (TMDs) have attracted considerable interest for spin-to-charge conversion due to their high spin-orbit coupling and lack of inversion symmetry in their crystal structure. However, reports of direct measurement of spin-to-charge conversion at TMD-based interfaces are very much limited. Here, we report on the room-temperature observation of a large spin-to-charge conversion arising from the interface of Ni80Fe20 (Py) and four distinct large-area (similar to 5 x 2 mm(2)) ML TMDs, namely, MoS2, MoSe2, WS2, and WSe2. We show that both spin mixing conductance and the Rashba efficiency parameter (lambda(IREE)) scale with the spin-orbit coupling strength of the ML TMD layers. The lambda(IREE) parameter is found to range between -0.54 and -0.76 nm for the four ML TMDs, demonstrating a large spin-to-charge conversion. Our findings reveal that the TMD/ferromagnet interface can be used for efficient generation and detection of spin current, opening new opportunities for novel spintronic devices.
|
|
| 10. |
- Behera, Nilamani, et al.
(författare)
-
Energy-Efficient W100-xTax/ Co-Fe-B/MgO Spin Hall Nano-Oscillators
- 2022
-
Ingår i: Physical Review Applied. - 2331-7019. ; 18:2
-
Tidskriftsartikel (refereegranskat)abstract
- We investigate a W-Ta alloying route to reduce the auto-oscillation threshold current densities and the power consumption of nanoconstriction based spin Hall nano-oscillators. Using spin-torque ferromagnetic resonance measurements on microbars of W100-xTax(5 nm)/Co-Fe-B(t)/MgO stacks with t=1.4, 1.8, and 2.0 nm, we measure a substantial improvement in both the spin-orbit torque efficiency and the spin Hall conductivity. We demonstrate a 34% reduction in auto-oscillation threshold current density, which translates into a 64% reduction in power consumption as compared with pure W-based spin Hall nano-oscillators. Our work demonstrates the promising aspects of W-Ta alloying for the energy-efficient operation of emerging spintronic devices.
|
|
