| 1. |
- Gupta, Pankhuri, et al.
(författare)
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Generation of out-of-plane polarized spin current in (permalloy, Cu)/EuS interfaces
- 2024
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Ingår i: PHYSICAL REVIEW B. - 2469-9950 .- 2469-9969. ; 109:6
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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.
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| 2. |
- Bonetti, Stefano, 1982-, et al.
(författare)
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Experimental evidence of self-localized and propagating spin wave modes in obliquely magnetized current-driven magnetic nanocontacts
- 2010
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 105:21, s. 217204-
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Tidskriftsartikel (refereegranskat)abstract
- Through detailed experimental studies of the angular dependence of spin wave excitations in nanocontact-based spin-torque oscillators, we demonstrate that two distinct spin wave modes can be excited, with different frequency, threshold currents, and frequency tunability. Using analytical theory and micromagnetic simulations we identify one mode as an exchange-dominated propagating spin wave, and the other as a self-localized nonlinear spin wave bullet. Wavelet-based analysis of the simulations indicates that the apparent simultaneous excitation of both modes results from rapid mode hopping induced by the Oersted field.
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| 3. |
- Bonetti, Stefano, et al.
(författare)
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Spin torque oscillator frequency versus magnetic field angle : The prospect of operation beyond 65 GHz
- 2009
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 94:10
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Tidskriftsartikel (refereegranskat)abstract
- We study the impact of the magnetic field angle on the oscillation frequency of a nanocontact spin torque oscillator (STO) in magnetic fields up to 2.1 T. A model based on a single nonlinear, nonpropagating spin wave mode is found to explain the experimental data. We observe oscillation frequencies as high as 46 GHz in high magnetic fields applied normal to the film plane, and we are able to extrapolate the maximum expected operating frequency to beyond 65 GHz for in-plane magnetic fields. The STO signal remains surprisingly strong at these conditions, which opens up for possible millimeter-wave applications.
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| 4. |
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| 5. |
- Chaurasiya, Avinash Kumar, et al.
(författare)
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Direct observation of unusual interfacial Dzyaloshinskii-Moriya interaction in graphene/NiFe/Ta heterostructures
- 2019
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Ingår i: Physical Review B. - 2469-9950 .- 2469-9969. ; 99:3, s. 1-6
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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.
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| 6. |
- Chen, Tingsu, et al.
(författare)
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Spin-Torque and Spin-Hall Nano-Oscillators
- 2016
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Ingår i: Proceedings of the IEEE. - : Institute of Electrical and Electronics Engineers (IEEE). - 0018-9219 .- 1558-2256. ; 104:10, s. 1919-1945
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Tidskriftsartikel (refereegranskat)abstract
- This paper reviews the state of the art in spin-torque and spin-Hall-effect-driven nano-oscillators. After a brief introduction to the underlying physics, the authors discuss different implementations of these oscillators, their functional properties in terms of frequency range, output power, phase noise, and modulation rates, and their inherent propensity for mutual synchronization. Finally, the potential for these oscillators in a wide range of applications, from microwave signal sources and detectors to neuromorphic computation elements, is discussed together with the specific electronic circuitry that has so far been designed to harness this potential.
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| 7. |
- Chen, Tingsu, 1987-, et al.
(författare)
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Spin-Torque and Spin-Hall Nano-Oscillators
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Ingår i: Proceedings of the IEEE. - 0018-9219 .- 1558-2256.
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Tidskriftsartikel (refereegranskat)abstract
- This paper reviews the state of the art in spin-torque and spin Hall effect driven nano-oscillators. After a brief introduction to the underlying physics, the authors discuss different implementations of these oscillators, their functional properties in terms of frequency range, output power, phase noise, and modulation rates, and their inherent propensity for mutual synchronization. Finally, the potential for these oscillators in a wide range of applications, from microwave signal sources and detectors to neuromorphic computation elements, is discussed together with the specific electronic circuitry that has so far been designed to harness this potential.
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| 8. |
- Chung, Sunjae, et al.
(författare)
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Spin transfer torque generated magnetic droplet solitons (invited)
- 2014
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 115:17
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Tidskriftsartikel (refereegranskat)abstract
- We present recent experimental and numerical advancements in the understanding of spin transfer torque generated magnetic droplet solitons. The experimental work focuses on nano-contact spin torque oscillators (NC-STOs) based on orthogonal (pseudo) spin valves where the Co fixed layer has an easy-plane anisotropy, and the [Co/Ni] free layer has a strong perpendicular magnetic anisotropy. The NC-STO resistance and microwave signal generation are measured simultaneously as a function of drive current and applied perpendicular magnetic field. Both exhibit dramatic transitions at a certain current dependent critical field value, where the microwave frequency drops 10 GHz, modulation sidebands appear, and the resistance exhibits a jump, while the magnetoresistance changes sign. We interpret these observations as the nucleation of a magnetic droplet soliton with a large fraction of its magnetization processing with an angle greater than 90 degrees, i.e., around a direction opposite that of the applied field. This interpretation is corroborated by numerical simulations. When the field is further increased, we find that the droplet eventually collapses under the pressure from the Zeeman energy. (C) 2014 AIP Publishing LLC.
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| 9. |
- Dumas, Randy K., et al.
(författare)
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Recent Advances in Nanocontact Spin-Torque Oscillators
- 2014
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Ingår i: IEEE transactions on magnetics. - 0018-9464 .- 1941-0069. ; 50:6, s. 4100107-
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Tidskriftsartikel (refereegranskat)abstract
- We present a comprehensive review of the most recent advances in nanocontact spin torque oscillators (NC-STOs). NC-STOs are highly tunable, with both applied magnetic field and dc, broadband microwave signal generators. As opposed to the nanopillar geometry, where the lateral cross section of the entire device has been confined to a typically <100 nm diameter, in NC-STOs, it is only the current injection site that has been laterally confined on top of an extended magnetic film stack. Three distinct material combinations will be discussed: 1) a Co/Cu/NiFe pseudospin valve (PSV) where both the Co and NiFe have a dominant in-plane anisotropy; 2) a Co/Cu/[Co/Ni](4) orthogonal PSV where the Co/Ni multilayer has a strong perpendicular anisotropy; and 3) a single NiFe layer with asymmetric non-magnetic Cu leads. We explore the rich and diverse magnetodynamic modes that can be generated in these three distinct sample geometries.
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| 10. |
- Dumas, Randy K., et al.
(författare)
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Recent Advances in Nanocontact Spin-Torque Oscillators
- 2014
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Ingår i: Ieee Transactions on Magnetics. - : Institute of Electrical and Electronics Engineers (IEEE). - 0018-9464 .- 1941-0069. ; 50:6
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Tidskriftsartikel (refereegranskat)abstract
- We present a comprehensive review of the most recent advances in nanocontact spin torque oscillators (NC-STOs). NC-STOs are highly tunable, with both applied magnetic field and dc, broadband microwave signal generators. As opposed to the nanopillar geometry, where the lateral cross section of the entire device has been confined to a typically <100 nm diameter, in NC-STOs, it is only the current injection site that has been laterally confined on top of an extended magnetic film stack. Three distinct material combinations will be discussed: 1) a Co/Cu/NiFe pseudospin valve (PSV) where both the Co and NiFe have a dominant in-plane anisotropy; 2) a Co/Cu/[Co/Ni](4) orthogonal PSV where the Co/Ni multilayer has a strong perpendicular anisotropy; and 3) a single NiFe layer with asymmetric non-magnetic Cu leads. We explore the rich and diverse magnetodynamic modes that can be generated in these three distinct sample geometries.
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