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  • 1
    Online-Ressource
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    Domain wall-magnetic tunnel junction spin–orbit torque devices and circuits for in-memory computing
    AIP Publishing ; 2021
    In:  Applied Physics Letters Vol. 118, No. 11 ( 2021-03-15)
    Details
    In: Applied Physics Letters, AIP Publishing, Vol. 118, No. 11 ( 2021-03-15)
    Kurzfassung: There are pressing problems with traditional computing, especially for accomplishing data-intensive and real-time tasks, that motivate the development of in-memory computing devices to both store information and perform computation. Magnetic tunnel junction memory elements can be used for computation by manipulating a domain wall, a transition region between magnetic domains, but the experimental study of such devices has been limited by high current densities and low tunnel magnetoresistance. Here, we study prototypes of three-terminal domain wall-magnetic tunnel junction in-memory computing devices that can address data processing bottlenecks and resolve these challenges by using perpendicular magnetic anisotropy, spin–orbit torque switching, and an optimized lithography process to produce average device tunnel magnetoresistance TMR = 171% and average resistance-area product RA = 29 Ω μm2, close to the RA of the unpatterned film. Device initialization variation in switching voltage is shown to be curtailed to 7%–10% by controlling the domain wall initial position, which we show corresponds to 90%–96% accuracy in a domain wall-magnetic tunnel junction full adder simulation. Repeatability of writing and resetting the device is shown. A circuit shows an inverter operation between two devices, showing that a voltage window is large enough, compared to the variation noise, to repeatably operate a domain wall-magnetic tunnel junction circuit. These results make strides in using magnetic tunnel junctions and domain walls for in-memory and neuromorphic computing applications.
    Materialart: Online-Ressource
    ISSN: 0003-6951 , 1077-3118
    URL: Article
    DOI: 10.1063/5.0038521
    RVK:
    UA 1000
    Sprache: Englisch
    Verlag: AIP Publishing
    Publikationsdatum: 2021
    ZDB Id: 211245-0
    ZDB Id: 1469436-0
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  • 2
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    Focused surface acoustic wave induced nano-oscillator based reservoir computing
    AIP Publishing ; 2022
    In:  Applied Physics Letters Vol. 121, No. 10 ( 2022-09-05)
    Details
    In: Applied Physics Letters, AIP Publishing, Vol. 121, No. 10 ( 2022-09-05)
    Kurzfassung: We demonstrate using micromagnetic simulations that a nanomagnet array excited by surface acoustic waves (SAWs) can work as a reservoir. An input nanomagnet is excited with focused SAW and coupled to several nanomagnets, seven of which serve as output nanomagnets. To evaluate memory effect and computing capability, we study the short-term memory (STM) and parity check (PC) capacities, respectively. The SAW (4 GHz carrier frequency) amplitude is modulated to provide a sequence of sine and square waves of 100 MHz frequency. The responses of the selected output nanomagnets are processed by reading the envelope of their magnetization states, which is used to train the output weights using the regression method. For classification, a random sequence of 100 square and sine wave samples is used, of which 80% are used for training, and the rest are used for testing. We achieve 100% training and 100% testing accuracy. The average STM and PC are calculated to be ∼4.69 and ∼5.39 bits, respectively, which is indicative of the proposed acoustically driven nanomagnet oscillator array being well suited for physical reservoir computing applications. The energy dissipation is ∼2.5 times lower than a CMOS-based echo-state network. Furthermore, the reservoir is able to accurately predict Mackey-Glass time series up to several time steps ahead. Finally, the ability to use high frequency SAW makes the nanomagnet reservoir scalable to small dimensions, and the ability to modulate the envelope at a lower frequency (100 MHz) adds flexibility to encode different signals beyond the sine/square waves classification and Mackey-Glass predication tasks demonstrated here.
    Materialart: Online-Ressource
    ISSN: 0003-6951 , 1077-3118
    URL: Article
    DOI: 10.1063/5.0110769
    RVK:
    UA 1000
    Sprache: Englisch
    Verlag: AIP Publishing
    Publikationsdatum: 2022
    ZDB Id: 211245-0
    ZDB Id: 1469436-0
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  • 3
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    On the Burning Rate of Carbon Monoxide
    AIP Publishing ; 1956
    In:  The Journal of Chemical Physics Vol. 25, No. 3 ( 1956-09-01), p. 448-457
    Details
    In: The Journal of Chemical Physics, AIP Publishing, Vol. 25, No. 3 ( 1956-09-01), p. 448-457
    Kurzfassung: Burning velocity measurements of the CO–O2–N2–H2O system were made with the flat-flame burner technique. The plan of experimentation was to vary the H2O content, the equivalence ratio, and the pressure, while holding the flame temperature constant by controlling the proportion of N2 in the mixture. The results could be represented empirically by the relation: vu2=3.8×106(CO)u(H2O)u0.5(P/Patmos)−0.24e−11 130/Tb,where vu is burning velocity (cm/sec), (CO)u and (H2O)u are mole fractions in the unburned gas, P is pressure, and Tb is burned-gas temperature. The Zeldovich, Frank-Kamenetsky, and Semenov equation was used to obtain an ``over-all'' activation energy (20 kcal) and frequency factor for the process, and the CO oxidation rate in this type of flame was then compared with the rate at which the CO forming as an intermediate in a lean hydrocarbon-air flame is oxidized in the downstream portion of such a flame. The comparison showed that, at comparable conditions, the CO oxidized 5.6 times as fast in the CO flame as in the hydrocarbon flame. Temperature traverses in hydrocarbon-air flames to which large proportions of H2O have been added showed the rate of CO oxidation to be slightly increased thereby. Equilibrium concentrations of the species H, OH, and O in the burned gases were calculated for a variety of CO–O2–N2–H2O mixtures, all at the same flame temperature, and correlations with burning velocity were sought. The square of the burning velocity was found to be directly proportional to (OH)b(CO)b0.72; alternatively, the group (H)b(O2)b0.136 gave equally good correlation. A third successful grouping was [(H)b+0.15(OH)b]½. The writers are not convinced that correlations of this type reveal the burning mechanism.
    Materialart: Online-Ressource
    ISSN: 0021-9606 , 1089-7690
    URL: Article
    DOI: 10.1063/1.1742944
    Sprache: Englisch
    Verlag: AIP Publishing
    Publikationsdatum: 1956
    ZDB Id: 3113-6
    ZDB Id: 1473050-9
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  • 4
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    Nonlinear instability in simulations of Large Plasma Device turbulence
    AIP Publishing ; 2013
    In:  Physics of Plasmas Vol. 20, No. 5 ( 2013-05-01)
    Details
    In: Physics of Plasmas, AIP Publishing, Vol. 20, No. 5 ( 2013-05-01)
    Kurzfassung: Several simulations of turbulence in the Large Plasma Device (LAPD) [Gekelman et al., Rev. Sci. Instrum. 62, 2875 (1991)] are energetically analyzed and compared with each other and with the experiment. The simulations use the same model, but different axial boundary conditions. They employ either periodic, zero-value, zero-derivative, or sheath axial boundaries. The linear stability physics is different between the scenarios because the various boundary conditions allow the drift wave instability to access different axial structures, and the sheath boundary simulation contains a conducting wall mode instability which is just as unstable as the drift waves. Nevertheless, the turbulence in all the simulations is relatively similar because it is primarily driven by a robust nonlinear instability that is the same for all cases. The nonlinear instability preferentially drives k∥=0 potential energy fluctuations, which then three-wave couple to k∥≠0 potential energy fluctuations in order to access the adiabatic response to transfer their energy to kinetic energy fluctuations. The turbulence self-organizes to drive this nonlinear instability, which destroys the linear eigenmode structures, making the linear instabilities ineffective.
    Materialart: Online-Ressource
    ISSN: 1070-664X , 1089-7674
    URL: Article
    DOI: 10.1063/1.4805084
    Sprache: Englisch
    Verlag: AIP Publishing
    Publikationsdatum: 2013
    ZDB Id: 1472746-8
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  • 5
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    Flame Structure Studies. III. Gas Sampling in a Low-Pressure Propane-Air Flame
    AIP Publishing ; 1955
    In:  The Journal of Chemical Physics Vol. 23, No. 10 ( 1955-10-01), p. 1875-1880
    Details
    In: The Journal of Chemical Physics, AIP Publishing, Vol. 23, No. 10 ( 1955-10-01), p. 1875-1880
    Kurzfassung: A previous investigation of this series showed that the temperature in a very lean, low-pressure propaneair flame continues rising for more than a centimeter downstream from the zone of blue luminosity. This suggested a two-stage combustion process: (I) the hydrocarbon oxidizes rapidly and luminously to carbon monoxide; (II) the carbon monoxide oxidizes more slowly to carbon dioxide. The current gas-sampling study has provided support for this hypothesis. Both water-cooled and uncooled probes have been used to obtain gas samples from the region of the flame just beyond the luminous zone. Tests were made to insure that reaction-quenching in the probe was effective and that flame disturbance was minimized. Gas analyses were performed both mass-spectrometrically and by a vacuum-freezing technique. Most of the samples were taken from a flame burning at 46 mm Hg abs pressure, with a mass air-propane ratio of 30. Substantial proportions of CO, and about 15 as much H2, were found as much as a centimeter downstream from the luminous zone, with probes of much less than a millimeter diam. The CO concentration decayed exponentially with distance; a kinetic analysis yielded a decay constant of 231 reciprocal seconds. (The flame temperature was 1605°K.) The H2/CO ratio was considerably less than that corresponding to water-gas equilibrium in the flame. No traces of hydrocarbons were found beyond the luminous zone.
    Materialart: Online-Ressource
    ISSN: 0021-9606 , 1089-7690
    URL: Article
    DOI: 10.1063/1.1740596
    Sprache: Englisch
    Verlag: AIP Publishing
    Publikationsdatum: 1955
    ZDB Id: 3113-6
    ZDB Id: 1473050-9
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  • 6
    Online-Ressource
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    Silicon double-injection electro-optic modulator with junction gate control
    AIP Publishing ; 1988
    In:  Journal of Applied Physics Vol. 63, No. 6 ( 1988-03-15), p. 1831-1839
    Details
    In: Journal of Applied Physics, AIP Publishing, Vol. 63, No. 6 ( 1988-03-15), p. 1831-1839
    Kurzfassung: Novel structures for carrier-induced electro-optical phase modulation in crystalline silicon are examined. A new dual-injection field-effect transistor structure for guided-wave light modulation at 1.3 μm is proposed and analyzed. It consists of an elongated cathode-anode-gate structure integrated in a rib waveguide. Dual-gate and single-gate control are considered. The overlap between the plasma charge density and the optical guided mode is computed. For a cathode-anode voltage of 0.32 V, the effective refractive index of the waveguide mode changes by ΔN=1×10−3 when the gate voltage is altered by 12 V. Numerical estimates of the bias current, pinchoff voltage, interaction length, and modulator speed are given.
    Materialart: Online-Ressource
    ISSN: 0021-8979 , 1089-7550
    URL: Article
    DOI: 10.1063/1.339878
    Sprache: Englisch
    Verlag: AIP Publishing
    Publikationsdatum: 1988
    ZDB Id: 220641-9
    ZDB Id: 3112-4
    ZDB Id: 1476463-5
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  • 7
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    Skyrmion logic clocked via voltage-controlled magnetic anisotropy
    AIP Publishing ; 2021
    In:  Applied Physics Letters Vol. 118, No. 19 ( 2021-05-10)
    Details
    In: Applied Physics Letters, AIP Publishing, Vol. 118, No. 19 ( 2021-05-10)
    Kurzfassung: Magnetic skyrmions are exciting candidates for energy-efficient computing due to their nonvolatility, detectability, and mobility. A recent proposal within the paradigm of reversible computing enables large-scale circuits composed of directly cascaded skyrmion logic gates, but it is limited by the manufacturing difficulty and energy costs associated with the use of notches for skyrmion synchronization. To overcome these challenges, we, therefore, propose a skyrmion logic synchronized via modulation of voltage-controlled magnetic anisotropy (VCMA). In addition to demonstrating the principle of VCMA synchronization through micromagnetic simulations, we also quantify the impacts of current density, skyrmion velocity, and anisotropy barrier height on skyrmion motion. Further micromagnetic results demonstrate the feasibility of cascaded logic circuits in which VCMA synchronizers enable clocking and pipelining, illustrating a feasible pathway toward energy-efficient large-scale computing systems based on magnetic skyrmions.
    Materialart: Online-Ressource
    ISSN: 0003-6951 , 1077-3118
    URL: Article
    DOI: 10.1063/5.0049024
    RVK:
    UA 1000
    Sprache: Englisch
    Verlag: AIP Publishing
    Publikationsdatum: 2021
    ZDB Id: 211245-0
    ZDB Id: 1469436-0
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  • 8
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    Electron attachment to propargyl chloride, 305–540 K
    AIP Publishing ; 2010
    In:  The Journal of Chemical Physics Vol. 133, No. 15 ( 2010-10-21)
    Details
    In: The Journal of Chemical Physics, AIP Publishing, Vol. 133, No. 15 ( 2010-10-21)
    Kurzfassung: Electron attachment to propargyl chloride (HC≡C–CH2Cl) was studied in a flowing-afterglow Langmuir-probe apparatus from 305 to 540 K. The sole ion product in this temperature range is Cl−. Electron attachment is very inefficient, requiring correction for a competing process of electron recombination with molecular cations produced in reaction between Ar+ and propargyl chloride and subsequent ion-molecule reactions. The electron attachment rate coefficient was measured to be 1.6×10−10 cm3 s−1 at 305 K and increased to 1.1×10−9 cm3 s−1 at 540 K.
    Materialart: Online-Ressource
    ISSN: 0021-9606 , 1089-7690
    URL: Article
    DOI: 10.1063/1.3505144
    Sprache: Englisch
    Verlag: AIP Publishing
    Publikationsdatum: 2010
    ZDB Id: 3113-6
    ZDB Id: 1473050-9
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  • 9
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    High-speed CMOS-free purely spintronic asynchronous recurrent neural network
    AIP Publishing ; 2023
    In:  APL Machine Learning Vol. 1, No. 1 ( 2023-03-01)
    Details
    In: APL Machine Learning, AIP Publishing, Vol. 1, No. 1 ( 2023-03-01)
    Kurzfassung: The exceptional capabilities of the human brain provide inspiration for artificially intelligent hardware that mimics both the function and the structure of neurobiology. In particular, the recent development of nanodevices with biomimetic characteristics promises to enable the development of neuromorphic architectures with exceptional computational efficiency. In this work, we propose biomimetic neurons comprised of domain wall-magnetic tunnel junctions that can be integrated into the first trainable CMOS-free recurrent neural network with biomimetic components. This paper demonstrates the computational effectiveness of this system for benchmark tasks and its superior computational efficiency relative to alternative approaches for recurrent neural networks.
    Materialart: Online-Ressource
    ISSN: 2770-9019
    URL: Article
    DOI: 10.1063/5.0129006
    Sprache: Englisch
    Verlag: AIP Publishing
    Publikationsdatum: 2023
    ZDB Id: 3161950-2
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  • 10
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    Magnetic domain wall neuron with lateral inhibition
    AIP Publishing ; 2018
    In:  Journal of Applied Physics Vol. 124, No. 15 ( 2018-10-21)
    Details
    In: Journal of Applied Physics, AIP Publishing, Vol. 124, No. 15 ( 2018-10-21)
    Kurzfassung: The development of an efficient neuromorphic computing system requires the use of nanodevices that intrinsically emulate the biological behavior of neurons and synapses. While numerous artificial synapses have been shown to store weights in a manner analogous to biological synapses, the challenge of developing an artificial neuron is impeded by the necessity to include leaking, integrating, firing, and lateral inhibition features. In particular, previous proposals for artificial neurons have required the use of external circuits to perform lateral inhibition, thereby decreasing the efficiency of the resulting neuromorphic computing system. This work therefore proposes a leaky integrate-and-fire neuron that intrinsically provides lateral inhibition, without requiring any additional circuitry. The proposed neuron is based on the previously proposed domain-wall magnetic tunnel junction devices, which have been proposed as artificial synapses and experimentally demonstrated for non-volatile logic. Single-neuron micromagnetic simulations are provided that demonstrate the ability of this neuron to implement the required leaking, integrating, and firing. These simulations are then extended to pairs of adjacent neurons to demonstrate, for the first time, lateral inhibition between neighboring artificial neurons. Finally, this intrinsic lateral inhibition is applied to a ten-neuron crossbar structure and trained to identify handwritten digits and shown via direct large-scale micromagnetic simulation for 100 digits to correctly identify the proper signal for 94% of the digits.
    Materialart: Online-Ressource
    ISSN: 0021-8979 , 1089-7550
    URL: Article
    DOI: 10.1063/1.5042452
    Sprache: Englisch
    Verlag: AIP Publishing
    Publikationsdatum: 2018
    ZDB Id: 220641-9
    ZDB Id: 3112-4
    ZDB Id: 1476463-5
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