| 1. |
- Arora, Monika, et al.
(författare)
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Magnetic Damping in Polycrystalline Thin-Film Fe-V Alloys
- 2021
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Ingår i: Physical Review Applied. - : American Physical Society. - 2331-7019. ; 15:5
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Tidskriftsartikel (refereegranskat)abstract
- We report on the magnetic damping properties of polycrystalline Fe-V alloy thin films that are deposited at room temperature. By varying the concentration of V in the alloy, the saturation magnetization can be adjusted from that of Fe to near zero. We show that exceptionally low values of the damping parameter can be maintained over the majority of this range, with a minimum damping at approximately 15%-20% V concentration. Such a minimum is qualitatively reproduced with ab initio calculations of the damping parameter, although at a concentration closer to 10% V. The measured intrinsic damping has a minimum value of (1.53 +/- 0.08) x 10-3, which is approximately a factor of 3 higher than our calculated value of 0.48 x 10-3. From first-principles theory, we outline the factors that are mainly responsible for the trend of the damping parameter in these alloys. In particular, the band structure and resulting damping mechanism is shown to change at V concentrations greater than approximately 35% V content.
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| 2. |
- Chen, K., et al.
(författare)
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Observation of a Chirality-Induced Exchange-Bias Effect
- 2019
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Ingår i: Physical Review Applied. - : AMER PHYSICAL SOC. - 2331-7019. ; 12:2
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Tidskriftsartikel (refereegranskat)abstract
- Chiral magnetism that manifests in the existence of skyrmions or chiral domain walls offers an alternative way for creating anisotropies in magnetic materials that might have large potential for application in future spintronic devices. Here we show experimental evidence for an alternative type of in-plane exchange-bias effect present at room temperature that is created from a chiral 90 degrees domain wall at the interface of a ferrimagnetic-ferromagnetic Dy-Co/Ni-Fe bilayer system. The chiral interfacial domain wall forms due to the exchange coupling of Ni-Fe and Dy-Co at the interface and the presence of Dzyaloshinskii-Moriya interaction in the Dy-Co layer. As a consequence of the preferred chirality of the interfacial domain wall, the sign of the exchange-bias effect can be reversed by changing the perpendicular orientation of the Dy-Co magnetization. The chirality-created tunable exchange bias in Dy-Co/Ni-Fe is very robust against high in-plane magnetic fields (mu H-0 <= 6 T) and does not show any aging effects. Therefore, it overcomes the limitations of conventional exchange-bias systems.
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| 3. |
- Feliciano, Gustavo T., et al.
(författare)
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Capacitive DNA Detection Driven by Electronic Charge Fluctuations in a Graphene Nanopore
- 2015
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Ingår i: Physical Review Applied. - 2331-7019. ; 3:3
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Tidskriftsartikel (refereegranskat)abstract
- The advent of parallelized automated methods for rapid whole-genome analysis has led to an exponential drop in costs, thus greatly accelerating biomedical research and discovery. Third-generation sequencing techniques, which would utilize the characteristic electrical conductance of the four different nucleotides, could facilitate longer base read lengths and an even lower price per genome. In this work, we propose and apply a quantum-classical hybrid methodology to quantitatively determine the influence of the solvent on the dynamics of DNA and the resulting electron transport properties of a prototypic sequencing device utilizing a graphene nanopore through which the nucleic-acid chain is threaded. Our results show that charge fluctuations in the nucleotides are responsible for characteristic conductance modulations in this system, which can be regarded as a field-effect transistor tuned by the dynamic aqueous environment.
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| 4. |
- Gandhi, Hemi H., et al.
(författare)
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Gold-Hyperdoped Germanium with Room-Temperature Sub-Band-Gap Optoelectronic Response
- 2020
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Ingår i: Physical Review Applied. - : AMER PHYSICAL SOC. - 2331-7019. ; 14:6
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Tidskriftsartikel (refereegranskat)abstract
- Short-wavelength-infrared (SWIR; 1.4-3.0 mu m) photodetection is important for various applications. Inducing a low-cost silicon-compatible material, such as germanium, to detect SWIR light would be advantageous for SWIR applications compared with using conventional (III-V or II-VI) SWIR materials. Here, we present a scalable nonequilibrium method for hyperdoping germanium with gold for dopant-mediated SWIR photodetection. Using ion implantation followed by nanosecond pulsed laser melting, we obtain a single-crystal material with a peak gold concentration of 3 x 10(19) cm(-3) (10(3) times the solubility limit). This hyperdoped germanium has fundamentally different optoelectronic properties from those of intrinsic and conventionally doped germanium. This material exhibits sub-band-gap absorption of light up to wavelengths of at least 3 mu m, with a sub-band-gap optical absorption coefficient comparable to that of commercial SWIR photodetection materials. We show that germanium hyperdoped with gold exhibits sub-band-gap SWIR photodetection at room temperature, in contrast with previous doped-germanium photodetector studies, which only show a low-temperature response. This material is a potential pathway to low-cost room-temperature silicon-compatible SWIR photodetection.
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| 5. |
- Gregefalk, Anton, et al.
(författare)
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Transitionless quantum driving in spin echo
- 2022
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Ingår i: Physical Review Applied. - : American Physical Society. - 2331-7019. ; 17
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Tidskriftsartikel (refereegranskat)abstract
- Spin echo can be used to refocus random dynamical phases caused by inhomogeneities in control fields and thereby retain the purity of a spatial distribution of quantum spins. This technique for accurate spin control is an essential ingredient in many applications, such as nuclear magnetic resonance, magnetic resonance imaging, and quantum information processing. Here, we show how all the elements of a spin echo sequence can be performed at high speed by means of transitionless quantum driving. This technique promises accurate control of rapid quantum spin evolution. We apply the scheme to universal nonadiabatic geometric single- and two-qubit gates in a nuclear magnetic resonance setting.
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| 6. |
- Holeňák, Radek, et al.
(författare)
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Assessing trajectory-dependent electronic energy loss of keV ions by a binary collision approximation code
- 2024
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Ingår i: Physical Review Applied. - : American Physical Society. - 2331-7019. ; 21:2
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Tidskriftsartikel (refereegranskat)abstract
- The inelastic energy deposition of energetic ions is a decisive quantity for numerous industrial-scale applications, such as sputtering and ion implantation, yet the underlying physics being governed by dynamic many-particle processes is commonly only qualitatively understood. Recently, transmission experiments on single-crystalline targets (Phys. Rev. Lett. 124, 096601 & Phys. Rev. A 102, 062803) revealed a complex energy scaling of the inelastic energy loss of low-energy ions heavier than protons along different trajectories. We use a Monte Carlo like binary collision approximation code equipped with an impact-parameter-dependent modeling of the inelastic energy losses to assess the role of local contributions to electronic excitations in these cases. We compare angular intensity distributions of calculated trajectories with experimental results for 50-keV 4He and 100-keV 29Si ions transmitted in a time-of-flight setup through single-crystalline silicon (001) foils with nominal thicknesses of 200 and 50 nm, respectively. In these calculations, we employ different models of electronic energy loss, i.e., local and nonlocal forms for light and heavy projectiles. We find that the vast number of projectiles are eventually channeled along their trajectories, regardless of the alignment of the crystal with respect to the incident beam. It is, however, only when local electronic energy loss is considered that the simulated two-dimensional maps and energy distributions show excellent agreement with the experimental results, where channeling leads to significantly reduced stopping, especially for heavier projectiles. We demonstrate the relevance of these effects for ion implantations by assessing the nonlinear and nonmonotonic scaling of the ion range with the thickness of a random surface layer.
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| 7. |
- Huang, Shuo, et al.
(författare)
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Strengthening Induced by MagnetoChemical Transition in Al-Doped Fe-Cr-Co-Ni High-Entropy Alloys
- 2018
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Ingår i: Physical Review Applied. - : American Physical Society. - 2331-7019. ; 10:6
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Tidskriftsartikel (refereegranskat)abstract
- Alloys with adjustable mechanical performance are of fundamental interest in material designs. Here, we investigate the magnetic- and chemical-ordering behavior of the ferromagnetic Fe-Cr-Co-Ni-Al-x (1 <= x <= 2.5) high-entropy alloys with the help of first-principle alloy theory. The lattice constants and the single- and polycrystalline elastic parameters for partially ordered and random structures are considered. In contrast to the trend found for the completely disordered phase, we demonstrate that ordering driven primarily by Al results in an enhanced Young's modulus, especially at high-Al concentrations, which is in line with the observed increase of the hardness for systems with a body-centered-cubic underlying lattice. The results suggest that outstanding strength and ductility can be realized by proper control of the ordering level in single- and multiphase high-entropy alloys.
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| 8. |
- Jacewicz, Marek, et al.
(författare)
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Temperature-Dependent Field Emission and Breakdown Measurements Using a Pulsed High-Voltage Cryosystem
- 2020
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Ingår i: Physical Review Applied. - College Park USA : American Physical Society (APS). - 2331-7019. ; 14:6
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Tidskriftsartikel (refereegranskat)abstract
- A variable-temperature pulsed high-voltage system has been constructed and a series of high-field measurements on copper electrodes have been carried out. The measurements are made at ambient to cryogenic temperatures and include conditioning, breakdown threshold, and field emission. A significant, up to 50%, increase in the breakdown threshold and remarkable stability of field emission are observed when cooled to cryogenic temperatures compared to room temperature. These results provide important experimental input for the development of quantitative theories and models of high-field processes as well as practical input for cryogenic radio-frequency systems.
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| 9. |
- Jiang, Sheng, et al.
(författare)
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Using Magnetic Droplet Nucleation to Determine the Spin Torque Efficiency and Asymmetry in Co-x(Ni,Fe)(1-x) Thin Films
- 2018
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Ingår i: Physical Review Applied. - : AMER PHYSICAL SOC. - 2331-7019. ; 10:5
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Tidskriftsartikel (refereegranskat)abstract
- We demonstrate how to extract the material-dependent spin-torque efficiency (epsilon) and asymmetry (lambda) from the field-current nucleation boundaries of magnetic droplet solitons in orthogonal nano-contact spintorque oscillators with Co-x(Ni80Fe20)(1-x), (x = 0 -1), fixed layers. As the perpendicular component of the fixed-layer magnetization plays a central role in governing droplet nucleation, the nucleation boundaries exhibit monotonic shifts towards higher perpendicular magnetic fields when the fixed-layer magnetization mu M-0(s, p) is tuned from 1.04 to 1.7 T. We then extract epsilon and lambda from fits to the nucleation boundaries and find that while epsilon does not vary with composition,lambda increases from 1.5 to 3 with increasing Co content. The analysis of droplet nucleation boundaries is hence a useful tool for the systematic study of both epsilon and lambda as functions of material composition.
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| 10. |
- Konishi, K., et al.
(författare)
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Intrinsic Mobility of Low-Density Electrons in Photoexcited Diamond
- 2022
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Ingår i: Physical Review Applied. - : American Physical Society. - 2331-7019. ; 17:3
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Extending the limit of charge-carrier mobility in semiconductors has been a long-standing pursuit in material science and its applications. Herein, we investigate the electron mobility via cyclotron resonance in undoped diamond under continuous-wave photoexcitation, whereby the density of charge carriers can be reduced to 108cm−3 or 1/10 of the previous detection limit [K. Konishi et al., Appl. Phys. Lett. 117, 212102 (2020)]. For low-density electrons, which obviate the effects of carrier-carrier scattering as a broadening mechanism, we observe an extraordinarily narrow cyclotron resonance spectrum. After correcting for the microwave power broadening, the highest intrinsic mobility value of 100×106 cm2V−1s−1 is obtained at 3 K, which is a 16-fold increase of the mobility compared with the previous record in diamond. Our result is beneficial for the design and application of diamond radiation detectors implemented for their practical use at cryogenic temperatures.
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