Rectification in Spin-Orbit Materials Using Low-Energy-Barrier Magnets

Recently there has been increasing activity to build dedicated Ising Machines to accelerate the solution of combinatorial optimization problems by expressing these problems as a ground-state search of the Ising model. A common theme of such Ising Machines is to tailor the physics of underlying hardware to the mathematics of the Ising model to improve some aspect of performance that is measured in speed to solution, energy consumption per solution or area footprint of the adopted hardware. One such approach to build an Ising spin, or a binary stochastic neuron (BSN), is a compact mixed-signal unit based on a low-barrier nanomagnet based design that uses a single magnetic tunnel junction (MTJ) and three transistors (3T-1MTJ) where the MTJ functions as a stochastic resistor (1SR). Such a compact unit can drastically reduce the area footprint of BSNs while promising massive scalability by leveraging the existing Magnetic RAM (MRAM) technology that has integrated 1T-1MTJ cells in ∼ Gbit densities. The 3T-1SR design however can be realized using different materials or devices that provide naturally fluctuating resistances. Extending previous work, we evaluate hardware BSNs from this general perspective by classifying necessary and sufficient conditions to design a fast and energy-efficient BSN that can be used in scaled Ising Machine implementations. We connect our device analysis to systems-level metrics by emphasizing hardware-independent figures-of-merit such as flips per second and dissipated energy per random bit that can be used to classify any Ising Machine.

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“…The expressions for correlation time and biasing current can be found in ref. 32,54,55,81 , in this appendix we derive the bias field.…”

Section: Discussionmentioning

confidence: 99%

Quantitative Evaluation of Hardware Binary Stochastic Neurons

Hassan

Datta

2021

Phys. Rev. Applied

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“…[2,3]) mechanisms, logic devices (see, e.g., Refs. [4,5]) for beyond conventional computing, spin battery [6], flexible electronics [7], metallic rectifier [8], etc. Over the past decade, a large number of materials have been studied as possible elements of the spin-charge interconversion including topological insulators (TI) [9][10][11][12][13][14], semiconductors [15,16], transition metals [3,[17][18][19][20][21][22][23][24], semimetals [25], oxides [26][27][28][29], antiferromagnets [30], superconductor [31], etc.…”

Section: Introductionmentioning

confidence: 99%

Unified Framework for Charge-Spin Interconversion in Spin-Orbit Materials

et al. 2021

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Materials with spin-orbit coupling are of great current interest for various spintronics applications due to the efficient electrical generation and detection of electron spins. Over the past decade, a large number of materials have been studied including topological insulators, transition metals, Kondo insulators, semimetals, semiconductors, oxide interfaces, etc., however, there is no unifying physical framework for understanding the physics and therefore designing a material system and devices with the desired properties. We present a model that binds together the experimental data observed on the wide variety of materials in a unified manner. We show that, in a material with a given spin orbit coupling, the density of states plays a key role in determining the spin-charge interconversion efficiency and a simple inverse relationship can be obtained. Remarkably, experimental data on spin voltage, obtained over the last decade on many different material systems closely follow such inverse relationship. Based on such analytical relationship, we further deduce two figure of merits of great current interest: the spin-orbit torque efficiency (for the direct effect) and the inverse Rashba-Edelstein effect length (for the inverse effect), which statistically show good agreement with the existing experimental data on wide varieties of materials.

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Spin–orbit torque rectifier for weak RF energy harvesting

Sayed

Salahuddin

Yablonovitch

2021

Applied Physics Letters

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We propose a rectifier concept, simultaneously utilizing the Hall effect and the spin–orbit-torque, that is well matched to the low impedance of antennas. This rectifier is promising for general radio detection and, particularly, for harvesting ambient weak radio signals, where conventional rectification fails to operate. The Hall effect and spin–orbit-torque are both proportional to current density, which improves inversely with the device cross-sectional area, providing a large signal at the nanoscale. A single device made using existing materials can provide 200 μV DC from 500 nW of radio frequency (RF) power. A series array of such devices can efficiently enhance the DC voltage to 300 mV while matching the receiver antenna impedance. Such magnetic devices can convert weak RF power into DC power with substantial efficiency at low voltage and low impedance where conventional semiconductor rectifiers fail.

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Rectification in Spin-Orbit Materials Using Low-Energy-Barrier Magnets

Cited by 3 publications

References 41 publications

Quantitative Evaluation of Hardware Binary Stochastic Neurons

Quantitative Evaluation of Hardware Binary Stochastic Neurons

Unified Framework for Charge-Spin Interconversion in Spin-Orbit Materials

Spin–orbit torque rectifier for weak RF energy harvesting

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