More Like this

1. CMOS-Free Magnetic Domain Wall Leaky Integrate-and-Fire Neurons with Intrinsic Lateral Inhibition

   https://doi.org/10.1109/ISCAS45731.2020.9180510  

   Hassan, Naimul; Brigner, Wesley H.; Hu, Xuan; Akinola, Otitoaleke G.; Bennett, Christopher H.; Marinella, Matthew J.; Garcia-Sanchez, Felipe; Incorvia, Jean Anne; Friedman, Joseph S. (October 2020, IEEE International Symposium on Circuits and Systems)

   null (Ed.)

   Spintronic devices, especially those based on motion of a domain wall (DW) through a ferromagnetic track, have received a significant amount of interest in the field of neuromorphic computing because of their non-volatility and intrinsic current integration capabilities. Many spintronic neurons using this technology have already been proposed, but they also require external circuitry or additional device layers to implement other important neuronal behaviors. Therefore, they result in an increase in fabrication complexity and/or energy consumption. In this work, we discuss three neurons that implement these functions without the use of additional circuitry or material layers. 

   more » « less
2. Semi-supervised learning and inference in domain-wall magnetic tunnel junction (DW-MTJ) neural networks

   https://doi.org/10.1117/12.2530308  

   Bennett, Christopher H.; Hassan, Naimul; Hu, Xuan; Incornvia, Jean Anne; Friedman, Joseph S.; Marinella, Matthew M. (September 2019, SPIE Spintronics XII)

   Advances in machine intelligence have sparked interest in hardware accelerators to implement these algorithms, yet embedded electronics have stringent power, area budgets, and speed requirements that may limit nonvolatile memory (NVM) integration. In this context, the development of fast nanomagnetic neural networks using minimal training data is attractive. Here, we extend an inference-only proposal using the intrinsic physics of domain-wall MTJ (DW-MTJ) neurons for online learning to implement fully unsupervised pattern recognition operation, using winner-take-all networks that contain either random or plastic synapses (weights). Meanwhile, a read-out layer trains in a supervised fashion. We find our proposed design can approach state-of-the-art success on the task relative to competing memristive neural network proposals, while eliminating much of the area and energy overhead that would typically be required to build the neuronal layers with CMOS devices. 

   more » « less
3. Unexpected Giant Microwave Conductivity in a Nominally Silent BiFeO ₃ Domain Wall

   https://doi.org/10.1002/adma.201905132  

   Huang, Yen‐Lin; Zheng, Lu; Chen, Peng; Cheng, Xiaoxing; Hsu, Shang‐Lin; Yang, Tiannan; Wu, Xiaoyu; Ponet, Louis; Ramesh, Ramamoorthy; Chen, Long‐Qing; et al (January 2020, Advanced Materials)

   Abstract Nanoelectronic devices based on ferroelectric domain walls (DWs), such as memories, transistors, and rectifiers, have been demonstrated in recent years. Practical high‐speed electronics, on the other hand, usually demand operation frequencies in the gigahertz (GHz) regime, where the effect of dipolar oscillation is important. Herein, an unexpected giant GHz conductivity on the order of 10³S m⁻¹is observed in certain BiFeO₃DWs, which is about 100 000 times greater than the carrier‐induced direct current (dc) conductivity of the same walls. Surprisingly, the nominal configuration of the DWs precludes the alternating current (ac) conduction under an excitation electric field perpendicular to the surface. Theoretical analysis shows that the inclined DWs are stressed asymmetrically near the film surface, whereas the vertical walls in a control sample are not. The resultant imbalanced polarization profile can then couple to the out‐of‐plane microwave fields and induce power dissipation, which is confirmed by the phase‐field modeling. Since the contributions from mobile‐carrier conduction and bound‐charge oscillation to the ac conductivity are equivalent in a microwave circuit, the research on local structural dynamics may open a new avenue to implement DW nano‐devices for radio‐frequency applications. 

   more » « less
4. Magnetic domain wall neuron with intrinsic leaking and lateral inhibition capability

   https://doi.org/10.1117/12.2528218  

   Brigner, Wesley H.; Hassan, Naimul; Hu, Xuan; Jiang-Wei, Lucian; Akinola, Otitoaleke G.; Garcia-Sanchez, Felipe; Pasquale, Massimo; Bennett, Christopher H.; Incorvia, Jean Anne; Friedman, Joseph S. (September 2019, SPIE Spintronics XII)

   The challenge of developing an efficient artificial neuron is impeded by the use of external CMOS circuits to perform leaking and lateral inhibition. The proposed leaky integrate-and-fire neuron based on the three terminal magnetic tunnel junction (3T-MTJ) performs integration by pushing its domain wall (DW) with spin-transfer or spin-orbit torque. The leaking capability is achieved by pushing the neurons’ DWs in the direction opposite of integration using a stray field from a hard ferromagnet or a non-uniform energy landscape resulting from shape or anisotropy variation. Firing is performed by the MTJ stack. Finally, analog lateral inhibition is achieved by dipolar field repulsive coupling from each neuron. An integrating neuron thus pushes slower neighboring neurons’ DWs in the direction opposite of integration. Applying this lateral inhibition to a ten-neuron output layer within a neuromorphic crossbar structure enables the identification of handwritten digits with 94% accuracy. 

   more » « less
5. Concerns in the Blurred Divisions Between Medical and Consumer Neurotechnology

   https://doi.org/10.1109/JSYST.2020.3032609  

   Paek, Andrew Y.; Brantley, Justin A.; Evans, Barbara J.; Contreras-Vidal, Jose L. (December 2020, IEEE Systems Journal)

   null (Ed.)

   Neurotechnology has traditionally been central to the diagnosis and treatment of neurological disorders. While these devices have initially been utilized in clinical and research settings, recent advancements in neurotechnology have yielded devices that are more portable, user friendly, and less expensive. These improvements allow laypeople to monitor their brain waves and interface their brains with external devices. Such improvements have led to the rise of wearable neurotechnology that is marketed to the consumer. While many of the consumer devices are marketed for innocuous applications, such as use in video games, there is potential for them to be repurposed for medical uses. How do we manage neurotechnologies that skirt the line between medical and consumer applications and what can be done to ensure consumer safety? Here, we characterize neurotechnology based on medical and consumer applications and summarize currently marketed uses of consumer-grade wearable headsets. We lay out concerns that may arise due to the similar claims associated with both medical and consumer devices, the possibility of consumer devices being repurposed for medical uses, and the potential for medical uses of neurotechnology to influence commercial markets related to employment and self-enhancement. 

   more » « less