20 results on '"Keng-Yuan Meng"'
Search Results
2. Observation of Nanoscale Skyrmions in SrIrO3/SrRuO3 Bilayers
- Author
-
David W. McComb, Bryan D. Esser, Jose Flores, Adam Ahmed, Mirko Baćani, Xue Zhao, Keng-Yuan Meng, Hans J. Hug, Andrada-Oana Mandru, Fengyuan Yang, and Núria Bagués
- Subjects
Materials science ,Condensed matter physics ,Field (physics) ,Mechanical Engineering ,Skyrmion ,Magnetic storage ,Oxide ,Bioengineering ,Heterojunction ,02 engineering and technology ,General Chemistry ,Atmospheric temperature range ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,law.invention ,chemistry.chemical_compound ,chemistry ,law ,General Materials Science ,Magnetic force microscope ,0210 nano-technology ,Nanoscopic scale - Abstract
Skyrmion imaging and electrical detection via topological Hall (TH) effect are two primary techniques for probing magnetic skyrmions, which hold promise for next-generation magnetic storage. However, these two kinds of complementary techniques have rarely been employed to investigate the same samples. We report the observation of nanoscale skyrmions in SrIrO3/SrRuO3 (SIO/SRO) bilayers in a wide temperature range from 10 to 100 K. The SIO/SRO bilayers exhibit a remarkable TH effect, which is up to 200% larger than the anomalous Hall (AH) effect at 5 K, and zero-field TH effect at 90 K. Using variable-temperature, high-field magnetic force microscopy (MFM), we imaged skyrmions as small as 10 nm, which emerge in the same field ranges as the TH effect. These results reveal a rich space for skyrmion exploration and tunability in oxide heterostructures.
- Published
- 2019
3. Local strain-dependent electronic structure and perpendicular magnetic anisotropy of a MnGaN 2D magnetic monolayer
- Author
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M. A. Barral, Arthur R. Smith, Tyler Erickson, Fengyuan Yang, V. Ferrari, Yingqiao Ma, Keng-Yuan Meng, and Diego Hunt
- Subjects
Materials science ,Physics and Astronomy (miscellaneous) ,Spintronics ,Condensed matter physics ,Spin polarization ,Scanning tunneling spectroscopy ,02 engineering and technology ,Electronic structure ,021001 nanoscience & nanotechnology ,01 natural sciences ,Condensed Matter::Materials Science ,Magnetic anisotropy ,Strain engineering ,0103 physical sciences ,Density of states ,General Materials Science ,010306 general physics ,0210 nano-technology ,Anisotropy - Abstract
Local strain-dependent spin-polarized electronic structure of a two-dimensional (2D) magnetic layer is an exciting property for practical applications. For example, it holds the promise for advanced ultrathin spintronic nanodevices with customized electronic and magnetic properties by local strain engineering. Here, we demonstrate that the spin-polarized electronic structure of a 2D manganese gallium nitride (MnGaN-2D) magnetic monolayer is sensitive to intrinsic local lattice strain, as proven by first-principles calculations and indicated by scanning tunneling spectroscopy measurements. Atomic resolution images reveal a highly non-Gaussian lattice spacing/strain distribution, while the spectroscopy reveals variations in the electronic density of states. Simulations of the MnGaN-2D monolayer based on first-principles calculations, including both isotropic and anisotropic strains, confirm a highly strain-dependent manganese partial density of states. Spin-orbit coupling is included which indicates either out-of-plane perpendicular magnetic anisotropy (PMA) or in-plane magnetic anisotropy, dependent on the type of strain whether compressive or tensile, suggesting that MnGaN-2D is magnetoelastic. The MnGaN-2D PMA is further supported by superconducting quantum interference device magnetometry measurements which reveal a high spin polarization of $\ensuremath{\sim}79$% at room temperature.
- Published
- 2020
4. Observation of Nanoscale Skyrmions in SrIrO
- Author
-
Keng-Yuan, Meng, Adam S, Ahmed, Mirko, Baćani, Andrada-Oana, Mandru, Xue, Zhao, Núria, Bagués, Bryan D, Esser, Jose, Flores, David W, McComb, Hans J, Hug, and Fengyuan, Yang
- Abstract
Skyrmion imaging and electrical detection via topological Hall (TH) effect are two primary techniques for probing magnetic skyrmions, which hold promise for next-generation magnetic storage. However, these two kinds of complementary techniques have rarely been employed to investigate the same samples. We report the observation of nanoscale skyrmions in SrIrO
- Published
- 2019
5. Exchange bias and exchange spring effects in Fe/CrN bilayers
- Author
-
Gregorio H. Cocoletzi, Andrew Foley, Fengyuan Yang, Keng-Yuan Meng, Noboru Takeuchi, R. Ponce-Pérez, Khan Alam, and Arthur R. Smith
- Subjects
010302 applied physics ,Materials science ,Acoustics and Ultrasonics ,Condensed matter physics ,Field (physics) ,Bilayer ,02 engineering and technology ,Spring (mathematics) ,Coercivity ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,chemistry.chemical_compound ,Exchange bias ,chemistry ,0103 physical sciences ,Thin film ,0210 nano-technology ,Chromium nitride ,Molecular beam epitaxy - Abstract
We studied exchange bias and exchange spring effects in magnetic bilayer thin films of Fe and CrN grown by molecular beam epitaxy. First, the relationships between exchange bias, coercivity, and blocking temperature and the Fe and CrN layers thicknesses are studied. Second, the exchange spring effect is observed and studied in all samples. The exchange spring breaks free at critical applied field strengths while creating planar domain walls at lower applied fields. First-principles calculations are performed to understand the magnetic interactions between the Fe and CrN layers at their interfaces. The calculations are key to understanding the experimental observations.
- Published
- 2020
6. Coexistence of Low Damping and Strong Magnetoelastic Coupling in Epitaxial Spinel Ferrite Thin Films
- Author
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Alpha T. N'Diaye, Matthew Gray, Krishnamurthy Mahalingam, Madelyn Hill, Yuri Suzuki, Maxwell Schmitt, Nian X. Sun, Joseph Peoples, Elke Arenholz, Brandon M. Howe, Benjamin Gray, Pallavi Dhagat, Greg Haugstad, Dongyao Li, Hyung Min Jeon, Albrecht Jander, Fengyuan Yang, Urusa S. Alaan, Keng-Yuan Meng, Sushant Mahat, Michael E. McConney, Padraic Shafer, Alexander C. Bornstein, Satoru Emori, and David G. Cahill
- Subjects
010302 applied physics ,Magnetization dynamics ,Materials science ,Condensed matter physics ,Spintronics ,Condensed Matter::Other ,Mechanical Engineering ,Magnetostriction ,02 engineering and technology ,021001 nanoscience & nanotechnology ,01 natural sciences ,Ferromagnetic resonance ,Condensed Matter::Materials Science ,Mechanics of Materials ,0103 physical sciences ,Magnetic damping ,Ferrite (magnet) ,Condensed Matter::Strongly Correlated Electrons ,General Materials Science ,Thin film ,0210 nano-technology ,Anisotropy - Abstract
Low-loss magnetization dynamics and strong magnetoelastic coupling are generally mutually exclusive properties due to opposing dependencies on spin-orbit interactions. So far, the lack of low-damping, magnetostrictive ferrite films has hindered the development of power-efficient magnetoelectric and acoustic spintronic devices. Here, magnetically soft epitaxial spinel NiZnAl-ferrite thin films with an unusually low Gilbert damping parameter (
- Published
- 2017
7. Strong Modulation of Spin Currents in Bilayer Graphene by Static and Fluctuating Proximity Exchange Fields
- Author
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Tianyu Liu, Jack Brangham, Jyoti Katoch, Roland Kawakami, Keng-Yuan Meng, Simranjeet Singh, Fengyuan Yang, Tiancong Zhu, and Michael E. Flatté
- Subjects
Condensed Matter - Materials Science ,Spin pumping ,Materials science ,Condensed Matter - Mesoscale and Nanoscale Physics ,Condensed matter physics ,Spin polarization ,Spintronics ,Graphene ,Materials Science (cond-mat.mtrl-sci) ,FOS: Physical sciences ,General Physics and Astronomy ,Spin engineering ,02 engineering and technology ,021001 nanoscience & nanotechnology ,01 natural sciences ,law.invention ,Magnetization ,Ferromagnetism ,law ,Mesoscale and Nanoscale Physics (cond-mat.mes-hall) ,0103 physical sciences ,Condensed Matter::Strongly Correlated Electrons ,010306 general physics ,0210 nano-technology ,Bilayer graphene - Abstract
Two dimensional (2D) materials provide a unique platform to explore the full potential of magnetic proximity driven phenomena, which can be further used for applications in next generation spintronic devices. Of particular interest is to understand and control spin currents in graphene by the magnetic exchange field of a nearby ferromagnetic material in graphene/ferromagnetic-insulator (FMI) heterostructures. Here, we present the experimental study showing the strong modulation of spin currents in graphene layers by controlling the direction of the exchange field due to FMI magnetization. Owing to clean interfaces, a strong magnetic exchange coupling leads to the experimental observation of complete spin modulation at low externally applied magnetic fields in short graphene channels. Additionally, we discover that the graphene spin current can be fully dephased by randomly fluctuating exchange fields. This is manifested as an unusually strong temperature dependence of the non-local spin signals in graphene, which is due to spin relaxation by thermally-induced transverse fluctuations of the FMI magnetization.
- Published
- 2017
8. In Situ Lorentz Differential Phase Contrast STEM Characterization of Rashba Interaction on Skyrmion Thin Films
- Author
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Mohit Randeria, Bryan D. Esser, Adam Ahmed, James Rowland, David W. McComb, Keng-Yuan Meng, Roland Kawakami, and Fengyuan Yang
- Subjects
0301 basic medicine ,In situ ,Materials science ,Condensed matter physics ,Skyrmion ,Lorentz transformation ,02 engineering and technology ,021001 nanoscience & nanotechnology ,Characterization (materials science) ,03 medical and health sciences ,symbols.namesake ,030104 developmental biology ,symbols ,Thin film ,0210 nano-technology ,Differential phase contrast ,Instrumentation - Published
- 2018
9. Large spin-orbit torque observed in epitaxial SrIrO3 thin films
- Author
-
Fengyuan Yang, Justin T. Hou, Jiahao Han, Luqiao Liu, Hailong Wang, Joseph Finley, Pengxiang Zhang, and Keng-Yuan Meng
- Subjects
010302 applied physics ,Spin pumping ,Materials science ,Chemical substance ,Physics and Astronomy (miscellaneous) ,Condensed matter physics ,02 engineering and technology ,021001 nanoscience & nanotechnology ,Epitaxy ,01 natural sciences ,Transition metal ,Ferromagnetism ,Sputtering ,0103 physical sciences ,Thin film ,0210 nano-technology ,Spin-½ - Abstract
Semimetallic iridate compound SrIrO3 epitaxial films have been deposited by off-axis sputtering, exhibiting excellent crystalline quality as well as smooth surfaces. By performing second-harmonic Hall measurements on a series of SrIrO3/Co1−xTbx bilayers, we quantitatively determined the spin-to-charge interconversion efficiency θ SH of SrIrO3 and discovered a systematic temperature and film thickness dependent evolution behavior. Notably, the measured θ SH reaches a remarkably large number of ∼1.1 at room temperature, which is significantly larger than the value of 5d transition metals and comparable to the values reported in some topological material systems. Our findings are further corroborated by ferromagnetic resonance-driven spin pumping studies in SrIrO3/Py bilayers, highlighting the significant opportunities offered by the iridate compounds in designing next-generation energy-efficient multifunctional spin Hall devices.
- Published
- 2019
10. Thickness dependence of spin Hall angle of Au grown onY3Fe5O12epitaxial films
- Author
-
Bryan D. Esser, P. Chris Hammel, Keng-Yuan Meng, Jack Brangham, Sisheng Yu, James C. Gallagher, Fengyuan Yang, Angela S. Yang, David W. McComb, and Shane P. White
- Subjects
Spin pumping ,Materials science ,Condensed matter physics ,Conductance ,02 engineering and technology ,Spin current ,021001 nanoscience & nanotechnology ,Epitaxy ,01 natural sciences ,Sputtering ,0103 physical sciences ,Spin diffusion ,Condensed Matter::Strongly Correlated Electrons ,010306 general physics ,0210 nano-technology ,Layer (electronics) ,Spin-½ - Abstract
We measure the spin Hall angle in Au layers of 5--100 nm thicknesses by spin pumping from ${\mathrm{Y}}_{3}\mathrm{F}{\mathrm{e}}_{5}{\mathrm{O}}_{12}$ epitaxial films grown by ultrahigh vacuum, off-axis sputtering. We observe a striking increase in the spin Hall angle for Au layers thinner than the measured spin diffusion length of 12.6 nm. In particular, the 5 nm Au layer shows a large spin Hall angle of 0.087, compared to those of 0.016 and 0.017 for the 50 and 100 nm Au layers, respectively, suggesting that the top surface plays a dominant role in spin Hall physics when the spin current is able to reach it. Other spin pumping related parameters, including Gilbert damping enhancement, interfacial spin mixing conductance, and spin current are also determined for Au layers of various thicknesses. Given the pervasive role of ultrathin films in electrical and spin transport applications, this result emphasizes the importance of considering the impact of the top surface and reveals the possibility of tuning critical spin parameters by film thickness.
- Published
- 2016
11. Robust Zero-Field Skyrmion Formation in FeGe Epitaxial Thin Films
- Author
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Keng-Yuan Meng, Bryan D. Esser, Fengyuan Yang, Hailong Wang, Jack Brangham, Dave W. McComb, and James C. Gallagher
- Subjects
Condensed Matter - Materials Science ,Materials science ,Condensed matter physics ,Field (physics) ,Skyrmion ,Epitaxial thin film ,General Physics and Astronomy ,Materials Science (cond-mat.mtrl-sci) ,FOS: Physical sciences ,02 engineering and technology ,021001 nanoscience & nanotechnology ,Epitaxy ,Condensed Matter::Mesoscopic Systems and Quantum Hall Effect ,01 natural sciences ,Magnetic field ,Condensed Matter::Materials Science ,Quality (physics) ,Hall effect ,Phase (matter) ,0103 physical sciences ,010306 general physics ,0210 nano-technology - Abstract
B20 phase magnetic materials, such as FeGe, have been of significant interests in recent years because they enable magnetic skyrmions, which can potentially lead to low energy cost spintronic applications. One major effort in this emerging field is the stabilization of skyrmions at room temperature and zero external magnetic field. We report the growth of phase-pure FeGe epitaxial thin films on Si(111) substrates by ultrahigh vacuum off-axis sputtering. The high crystalline quality of the FeGe films was confirmed by x-ray diffraction and scanning transmission electron microscopy. Hall effect measurements reveal strong topological Hall effect after subtracting out the ordinary and anomalous Hall effects, demonstrating the formation of high density skyrmions in FeGe films between 5 and 275 K. In particular, substantial topological Hall effect was observed at zero magnetic field, showing a robust skyrmion phase without the need of an external magnetic field.
- Published
- 2016
12. Controlling and patterning the effective magnetization in Y3Fe5O12 thin films using ion irradiation
- Author
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S. P. White, Jack Brangham, Fengyuan Yang, P. C. Hammel, William Ruane, Keng-Yuan Meng, and Denis V. Pelekhov
- Subjects
Materials science ,Condensed matter physics ,General Physics and Astronomy ,Resonance ,02 engineering and technology ,021001 nanoscience & nanotechnology ,01 natural sciences ,Focused ion beam ,Ferromagnetic resonance ,lcsh:QC1-999 ,Ion ,Magnetization ,Ferrimagnetism ,Magnet ,0103 physical sciences ,Thin film ,010306 general physics ,0210 nano-technology ,lcsh:Physics - Abstract
We report an approach to controlling the effective magnetization (Meff), a combination of the saturation magnetization and uniaxial anisotropy, of the ferrimagnet Y3Fe5O12 (YIG) using different species of ions: He+ and Ga+. The effective magnetization can be tuned as a function of the fluence, with He + providing the largest effect. We quantified the change in effective magnetization through an angular dependence of the ferromagnetic resonance before and after irradiation. Increases in 4πMeff were observed to be as much as 400 G with only a 15% increase in Gilbert damping, α (from 8.2e-4 to 9.4e-4). This result was combined with a method for accurate ion pattering, a focused ion beam, providing a mechanism for shaping the magnetic environment with submicron precision. We observe resonance modes localized by ion patterning of micron-sized dots, whose resonances match well with micromagnetic simulations. This technique offers a flexible tool for precision nanoscale control and characterization of the magnetic properties of YIG.
- Published
- 2018
13. Magnetostrictive iron gallium thin films grown onto antiferromagnetic manganese nitride: Structure and magnetism
- Author
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David C. Ingram, Arthur R. Smith, Andrada-Oana Mandru, James C. Gallagher, A. L. Richard, Fengyuan Yang, Joseph Corbett, and Keng-Yuan Meng
- Subjects
Materials science ,Physics and Astronomy (miscellaneous) ,Magnetic domain ,Magnetism ,chemistry.chemical_element ,02 engineering and technology ,Substrate (electronics) ,Manganese ,Nitride ,01 natural sciences ,law.invention ,Condensed Matter::Materials Science ,Nuclear magnetic resonance ,law ,Condensed Matter::Superconductivity ,0103 physical sciences ,010302 applied physics ,Condensed matter physics ,equipment and supplies ,021001 nanoscience & nanotechnology ,Magnetic shape-memory alloy ,chemistry ,Condensed Matter::Strongly Correlated Electrons ,Magnetic force microscope ,Scanning tunneling microscope ,0210 nano-technology ,human activities - Abstract
We report structural and magnetic properties of magnetostrictive Fe100−xGax (x ≈ 15) alloys when deposited onto antiferromagnetic manganese nitride and non-magnetic magnesium oxide substrates. From X-ray diffraction measurements, we find that the FeGa films are single crystalline. Scanning tunneling microscopy imaging reveals that the surface morphologies are dictated by the growth temperature, composition, and substrate. The magnetic properties can be tailored by the substrate, as found by magnetic force microscopy imaging and vibrating sample magnetometry measurements. In addition to pronounced tetragonal deformations, depositing FeGa onto manganese nitride leads to the formation of stripe-like magnetic domain patterns and to the appearance of perpendicular magnetic anisotropy.
- Published
- 2016
14. Exceptionally high magnetization of stoichiometric Y3Fe5O12 epitaxial films grown on Gd3Ga5O12
- Author
-
Bryan D. Esser, Shane P. White, Rohan Adur, William Ruane, Keng-Yuan Meng, Sarah Dunsiger, Jack Brangham, James C. Gallagher, Sisheng Yu, Fengyuan Yang, Michael R. Page, David W. McComb, Angela S. Yang, and P. Chris Hammel
- Subjects
Materials science ,Valence (chemistry) ,Physics and Astronomy (miscellaneous) ,Condensed matter physics ,Magnetometer ,02 engineering and technology ,Sputter deposition ,021001 nanoscience & nanotechnology ,Epitaxy ,Magnetic hysteresis ,01 natural sciences ,Ferromagnetic resonance ,law.invention ,Condensed Matter::Materials Science ,Magnetization ,law ,Condensed Matter::Superconductivity ,0103 physical sciences ,010306 general physics ,0210 nano-technology ,Single crystal - Abstract
The saturation magnetization of Y3Fe5O12 (YIG) epitaxial films 4 to 250 nm in thickness has been determined by complementary measurements including the angular and frequency dependencies of the ferromagnetic resonance fields as well as magnetometry measurements. The YIG films exhibit state-of-the-art crystalline quality, proper stoichiometry, and pure Fe3+ valence state. The values of YIG magnetization obtained from all the techniques significantly exceed previously reported values for single crystal YIG and the theoretical maximum. This enhancement of magnetization, not attributable to off-stoichiometry or other defects in YIG, opens opportunities for tuning magnetic properties in epitaxial films of magnetic insulators.
- Published
- 2016
15. Magnetostrictive iron gallium thin films grown onto antiferromagnetic manganese nitride: Structure and magnetism.
- Author
-
Mandru, Andrada-Oana, Corbett, Joseph P., Richard, Andrea L., Gallagher, James, Keng-Yuan Meng, Ingram, David C., Fengyuan Yang, and Smith, Arthur R.
- Subjects
IRON ,GALLIUM ,THIN films ,ANTIFERROMAGNETIC materials ,MANGANESE nitrides ,MAGNETISM - Abstract
We report structural and magnetic properties of magnetostrictive Fe
100-x Gax (x ≈ 15) alloys when deposited onto antiferromagnetic manganese nitride and non-magnetic magnesium oxide substrates. From X-ray diffraction measurements, we find that the FeGa films are single crystalline. Scanning tunneling microscopy imaging reveals that the surface morphologies are dictated by the growth temperature, composition, and substrate. The magnetic properties can be tailored by the substrate, as found by magnetic force microscopy imaging and vibrating sample magnetometry measurements. In addition to pronounced tetragonal deformations, depositing FeGa onto manganese nitride leads to the formation of stripe-like magnetic domain patterns and to the appearance of perpendicular magnetic anisotropy. [ABSTRACT FROM AUTHOR]- Published
- 2016
- Full Text
- View/download PDF
16. Exceptionally high magnetization of stoichiometric Y3Fe5O12 epitaxial films grown on Gd3Ga5O12.
- Author
-
Gallagher, James C., Yang, Angela S., Brangham, Jack T., Esser, Bryan D., White, Shane P., Page, Michael R., Keng-Yuan Meng, Sisheng Yu, Adur, Rohan, Ruane, William, Dunsiger, Sarah R., McComb, David W., Fengyuan Yang, and Hammel, P. Chris
- Subjects
MAGNETIZATION ,FERROMAGNETIC resonance ,CRYSTALLINE polymers ,STOICHIOMETRY ,MAGNETIC insulators - Abstract
The saturation magnetization of Y
3 Fe5 O12 (YIG) epitaxial films 4 to 250 nm in thickness has been determined by complementary measurements including the angular and frequency dependencies of the ferromagnetic resonance fields as well as magnetometry measurements. The YIG films exhibit state-of-the-art crystalline quality, proper stoichiometry, and pure Fe3+ valence state. The values of YIG magnetization obtained from all the techniques significantly exceed previously reported values for single crystal YIG and the theoretical maximum. This enhancement of magnetization, not attributable to off-stoichiometry or other defects in YIG, opens opportunities for tuning magnetic properties in epitaxial films of magnetic insulators. [ABSTRACT FROM AUTHOR]- Published
- 2016
- Full Text
- View/download PDF
17. Exchange bias and exchange spring effects in Fe/CrN bilayers.
- Author
-
Khan Alam, Keng-Yuan Meng, Rodrigo Ponce-Pérez, Gregorio H Cocoletzi, Noboru Takeuchi, Andrew Foley, Fengyuan Yang, and Arthur R Smith
- Subjects
- *
MOLECULAR beam epitaxy , *DOMAIN walls (String models) , *EXCHANGE , *SPRING break , *THIN films - Abstract
We studied exchange bias and exchange spring effects in magnetic bilayer thin films of Fe and CrN grown by molecular beam epitaxy. First, the relationships between exchange bias, coercivity, and blocking temperature and the Fe and CrN layers thicknesses are studied. Second, the exchange spring effect is observed and studied in all samples. The exchange spring breaks free at critical applied field strengths while creating planar domain walls at lower applied fields. First-principles calculations are performed to understand the magnetic interactions between the Fe and CrN layers at their interfaces. The calculations are key to understanding the experimental observations. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
18. Thickness dependence of spin Hall angle of Au grown on Y3Fe5O12 epitaxial films.
- Author
-
Brangham, Jack T., Keng-Yuan Meng, Yang, Angela S., Gallagher, James C., Esser, Bryan D., White, Shane P., Sisheng Yu, McComb, David W., Hammel, P. Chris, and Fengyuan Yang
- Subjects
- *
EPITAXY , *SPIN Hall effect , *SILVER - Abstract
We measure the spin Hall angle in Au layers of 5-100 nm thicknesses by spin pumping from Y3Fe5O12 epitaxial films grown by ultrahigh vacuum, off-axis sputtering. We observe a striking increase in the spin Hall angle for Au layers thinner than the measured spin diffusion length of 12.6 nm. In particular, the 5 nm Au layer shows a large spin Hall angle of 0.087, compared to those of 0.016 and 0.017 for the 50 and 100 nm Au layers, respectively, suggesting that the top surface plays a dominant role in spin Hall physics when the spin current is able to reach it. Other spin pumping related parameters, including Gilbert damping enhancement, interfacial spin mixing conductance, and spin current are also determined for Au layers of various thicknesses. Given the pervasive role of ultrathin films in electrical and spin transport applications, this result emphasizes the importance of considering the impact of the top surface and reveals the possibility of tuning critical spin parameters by film thickness. [ABSTRACT FROM AUTHOR]
- Published
- 2016
- Full Text
- View/download PDF
19. Exceptionally high magnetization of stoichiometric Y3Fe5O12 epitaxial films grown on Gd3Ga5O12.
- Author
-
Gallagher, James C., Yang, Angela S., Brangham, Jack T., Esser, Bryan D., White, Shane P., Page, Michael R., Keng-Yuan Meng, Sisheng Yu, Adur, Rohan, Ruane, William, Dunsiger, Sarah R., McComb, David W., Fengyuan Yang, and Hammel, P. Chris
- Subjects
- *
MAGNETIZATION , *FERROMAGNETIC resonance , *CRYSTALLINE polymers , *STOICHIOMETRY , *MAGNETIC insulators - Abstract
The saturation magnetization of Y3Fe5O12 (YIG) epitaxial films 4 to 250 nm in thickness has been determined by complementary measurements including the angular and frequency dependencies of the ferromagnetic resonance fields as well as magnetometry measurements. The YIG films exhibit state-of-the-art crystalline quality, proper stoichiometry, and pure Fe3+ valence state. The values of YIG magnetization obtained from all the techniques significantly exceed previously reported values for single crystal YIG and the theoretical maximum. This enhancement of magnetization, not attributable to off-stoichiometry or other defects in YIG, opens opportunities for tuning magnetic properties in epitaxial films of magnetic insulators. [ABSTRACT FROM AUTHOR]
- Published
- 2016
- Full Text
- View/download PDF
20. Strong Modulation of Spin Currents in Bilayer Graphene by Static and Fluctuating Proximity Exchange Fields.
- Author
-
Singh, Simranjeet, Katoch, Jyoti, Tiancong Zhu, Keng-Yuan Meng, Tianyu Liu, Brangham, Jack T., Fengyuan Yang, Flatté, Michael E., and Kawakami, Roland K.
- Subjects
- *
FERROMAGNETIC materials , *GRAPHENE , *FLUCTUATIONS (Physics) - Abstract
Two-dimensional materials provide a unique platform to explore the full potential of magnetic proximity-driven phenomena, which can be further used for applications in next-generation spintronic devices. Of particular interest is to understand and control spin currents in graphene by the magnetic exchange field of a nearby ferromagnetic material in graphene-ferromagnetic-insulator (FMI) heterostructures. Here, we present the experimental study showing the strong modulation of spin currents in graphene layers by controlling the direction of the exchange field due to FMI magnetization. Owing to clean interfaces, a strong magnetic exchange coupling leads to the experimental observation of complete spin modulation at low externally applied magnetic fields in short graphene channels. Additionally, we discover that the graphene spin current can be fully dephased by randomly fluctuating exchange fields. This is manifested as an unusually strong temperature dependence of the nonlocal spin signals in graphene, which is due to spin relaxation by thermally induced transverse fluctuations of the FMI magnetization. [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
- View/download PDF
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