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Search Publications by: William Rippard (Fed)

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Displaying 1 - 25 of 60

Mutual control of stochastic switching for two electrically coupled superparamagnetic tunnel junctions

August 19, 2021
Author(s)
Philippe Talatchian, Matthew Daniels, Advait Madhavan, Matthew Pufall, Emilie Jue, William Rippard, Jabez J. McClelland, Mark Stiles
Superparamagnetic tunnel junctions (SMTJs) are promising sources for the randomness required by some compact and energy-efficient computing schemes. Coupling them gives rise to collective behavior that could be useful for cognitive computing. We use a

Distance Computation Based on Coupled Spin-Torque Oscillators: Application to Image Processing

September 1, 2020
Author(s)
Minsuk Koo, Matthew Pufall, Yong Shim, Anthony B. Kos, Gyorgy Csaba, Wolfgang Porod , William Rippard, Kaushik Roy
Recent research on nano-oscillators has shown the possibility of using a coupled-oscillator network as a core-computing primitive for non-Boolean computation. The spin-torque oscillator (STO) is an attractive candidate because it is CMOS compatible, highly

Synaptic weighting in single flux quantum neuromorphic computing

January 22, 2020
Author(s)
Michael L. Schneider, Christine A. Donnelly, Ian W. Haygood, Alex Wynn, Stephen E. Russek, Manuel C. Castellanos Beltran, Paul D. Dresselhaus, Peter F. Hopkins, Matthew R. Pufall, William H. Rippard
Josephson junctions act as a natural spiking neuron-like device for neuromorphic computing. By leveraging the advances recently demonstrated in digital single flux quantum (SFQ) circuits and using recently demonstrated magnetic Josephson junction (MJJ)

Energy efficient single flux quantum based neuromorphic computing

November 8, 2018
Author(s)
Michael Schneider, Christine A. Donnelly, Stephen E. Russek, Burm Baek, Matthew Pufall, Pete Hopkins, William Rippard
Many neuromorphic hardware technologies are being explored for their potential to increase the efficiency of computing certain problems, and thus facilitate machine learning with greater energy efficiency and or with more complexity. Among the technologies

Anomalous Supercurrent Modulation in Josephson Junctions With Ni-Based Barriers

May 15, 2018
Author(s)
Burm Baek, Michael L. Schneider, Matthew R. Pufall, William H. Rippard
We investigate the supercurrent transport characteristics of Ni-barrier Josephson junctions with various barrier multilayer structures. Our device fabrication and magneto-electrical measurement methods provide high enough statistics and rigor necessary for

Asymmetric and partial injection locking of a three-terminal spin-torque oscillator

March 9, 2018
Author(s)
Emilie M. Jue, Matthew R. Pufall, William H. Rippard
We measure the injection locking of a three-terminal spin-torque oscillator (STO) excited by a spin-orbit torque. The device consists of a magnetic tunnel junction on top of a Pt wire. A DC and an AC current are applied through the Pt wire to respectively

Ultralow power artificial synapses using nanotextured magnetic Josephson junctions

January 28, 2018
Author(s)
Michael L. Schneider, Christine A. Donnelly, Stephen E. Russek, Burm Baek, Matthew R. Pufall, Peter F. Hopkins, Paul D. Dresselhaus, Samuel P. Benz, William H. Rippard
Neuromorphic computing is a promising avenue to dramatically improve the efficiency of certain computational tasks, such as perception and decision making. Neuromorphic systems are currently being developed for critical applications ranging from self

Stochastic Single Flux Quantum Neuromorphic Computing using Magnetically Tunable Josephson Junctions

October 16, 2016
Author(s)
Stephen E. Russek, Christine A. Donnelly, Michael Schneider, Burm Baek, Matthew Pufall, William Rippard, Pete Hopkins, Paul Dresselhaus, Samuel P. Benz
Abstract— Single flux quantum (SFQ) circuits form a natural neuromorphic technology with SFQ pulses and superconducting transmission lines simulating action potentials and axons, respectively. Here we present a new component, magnetic Josephson junctions

Physical implementation of coherently-coupled oscillator networks

August 13, 2015
Author(s)
Matthew R. Pufall, William H. Rippard, Gyorgy Csaba, Wolfgang Porod, George Bourianoff, Dmitri Nikonov
We present a combined experimental and simulation study of the physical implementation of coherently coupled oscillator networks composed of spin-torque oscillators (STOs). Based on published works and on our recent experiments, we review the behavior of

Nanoscale Spin Valve Josephson Junction Devices

April 14, 2015
Author(s)
Burm Baek, William H. Rippard, Matthew R. Pufall, Samuel P. Benz, Stephen E. Russek, Horst Rogalla, Paul D. Dresselhaus
Traditionally, superconductivity and magnetism have had a mutually exclusive relationship. However, the physics of superconductor-ferromagnet hybrid structures turned out to be far from being simply destructive, which has led to the hope of a new breed of

Spin-transfer torque switching observed in nanopillar superconducting-magnetic hybrid Josephson junctions

January 9, 2015
Author(s)
Burm Baek, William H. Rippard, Matthew R. Pufall, Samuel P. Benz, Stephen E. Russek, Horst Rogalla, Paul D. Dresselhaus
Combining superconducting and magnetic materials to create novel superconducting devices has been motivated by the discovery of the Josephson critical current (Ics) oscillations with magnetic layer thickness and the demonstration of devices with switchable

Correlation of anomalous write error rate and ferromagnetic resonance spectrum in spin-transfer-torque-magnetic-random-access-memory devices containing in-plane free layers

May 28, 2014
Author(s)
Eric R. Evarts, Ranko R. Heindl, William H. Rippard, Matthew R. Pufall
In a small fraction of magnetic-tunnel-junction-based MRAM devices with in-plane free layers, the write error rates (WERs) are higher than expected on the basis of the macrospin or quasi-uniform magnetization reversal models. In devices with increased WERs

Hybrid superconducting-magnetic memory device using competing order parameters

May 28, 2014
Author(s)
Burm Baek, William H. Rippard, Samuel P. Benz, Stephen E. Russek, Paul D. Dresselhaus
The quantum behavior of Josephson junctions is often exploited to produce superconducting devices with outstanding performance. Josephson junctions can also be used in circuits that perform logic operations in picoseconds and may enable high-performance

Time Required to Injection-Lock Spin Torque Nanoscale Oscillators

October 29, 2013
Author(s)
William H. Rippard, Matthew R. Pufall, Anthony B. Kos
We have injection-locked a spin-transfer oscillator to a second-harmonic electrical input signal and measured the relative phase and amplitude of the device output as a function of DC current under steady-state conditions. The relative phase of the device