A novel transverse read technique for domain-wall “racetrack” memories.

 Roxy, Kawsher, Sébastien Ollivier, Arifa Hoque, Stephen Longofono, Alex K. Jones, and Sanjukta Bhanja. "A novel transverse read technique for domain-wall “racetrack” memories." IEEE Transactions on Nanotechnology 19 (2020): 648-652.

 

Citation in bibtex

@ARTICLE{9158538,
  author={Roxy, Kawsher and Ollivier, Sébastien and Hoque, Arifa and Longofono, Stephen and Jones, Alex K. and Bhanja, Sanjukta},
  journal={IEEE Transactions on Nanotechnology}, 
  title={A Novel Transverse Read Technique for Domain-Wall “Racetrack” Memories}, 
  year={2020},
  volume={19},
  number={},
  pages={648-652},
  doi={10.1109/TNANO.2020.3014091}}

Abstract:

Domain-wall memory (DWM), an extension to spin transfer torque-magnetic random access memory (STT-MRAM), stores multiple bits, each bit in an individual domain within a nanowire. The access mechanism of a DWM is carried out with the help of an access point orthogonal to the nanowire, similar to a conventional magneto-tunnel junction (MTJ) of STT-MRAM. In this context, the MTJ free layer is one of the domains of the nanowire. Prior to an access, the desired bit is brought under the access point by shifting, and then its spin orientation is detected by a traditional sensing circuit or overwritten with a write current. However, the nanowire can also be viewed as a multi-level cell (MLC)-like device when tested with an end-to-end current. Based on this observation, we devised a novel transverse read (TR) technique to detect the number of `1's stored in a DWM without shifting any domains. TR is non-destructive and requires ultra-low power insomuch as the TR current is small compared to the shifting current. The TR has interesting applications in DWM such as a neuron in a neuromorphic engine, a multi-bit digital storage device, or as a fault tolerance tool for shifting reliability in DWM memories. In this work, we experimentally demonstrate the feasibility of TR in both perpendicular and in-plane magnetic anisotropy nanowires and determine the critical requirements of successful TR operation.

 

Patents

• Magnetic memory physically unclonable functions

  Patent number: 10536281

  Abstract: A magnetic random access memory (MRAM) physically unclonable function (PUF) device that uses the geometric variations in magnetic memory cells to generate a random PUF response is described herein. Within the MRAM, one or more magnetic memory cells can be used for the PUF. The PUF response is generated by destabilizing the one or more magnetic memory cells and then allowing them to relax. The MRAM PUF has also a relatively small footprint among all other silicon PUFs. Timing and control signals for the MRAM PUF are also described along with power and delay characteristics for use with field and spin transfer torque driven destabilization operations.

  Type: Grant

  Filed: May 28, 2015

  Date of Patent: January 14, 2020

  Assignee: University of South Florida

  Inventors: Jayita Das, Kevin P. Scott, Drew H. Burgett, Srinath Rajaram, Sanjukta Bhanja

• Materials and methods for detecting and monitoring edema and related conditions

  Patent number: 10517533

  Abstract: Provided is a Coupled Domain Sensor (CDS) that can be used to, for example, evaluate hydration and occlusion of blood in patients with edema using electrical and optical measurements. Advantageously, the CDS provides a quicker, more effective and accurate way of monitoring this medical condition.

  Type: Grant

  Filed: May 16, 2016

  Date of Patent: December 31, 2019

  Assignees: The Florida International University Board of Trustees, University of South Florida

  Inventors: Shekhar Bhansali, Karina Rincon, Jessica Ramella-Roman, Sanjukta Bhanja

• Magnetic coprocessor and method of use

  Patent number: 10198402

  Abstract: A magnetic system for solving one or more quadratic optimization problems by associating each of a plurality of variables of a quadratic optimization problem with a nanomagnet subset of a nanomagnet array, driving the nanomagnets of the nanomagnet subset to an excited state, allowing the nanomagnets of the nanomagnet subset to enter a relaxed state after being driven to an excited state, wherein the nanomagnets magnetically couple with one another in the relaxed state to minimize the total magnetic coupling energy of the nanomagnet array, and sensing a magnetic coupling of the nanomagnets of the nanomagnet subset to solve the quadratic optimization problem.

  Type: Grant

  Filed: July 31, 2017

  Date of Patent: February 5, 2019

  Assignee: University of South Florida

  Inventors: Sanjukta Bhanja, Sudeep Sarkar, Ravi Panchumarthy, Dinuka K. Karunaratne

• Magnetic coprocessor and method of use

  Patent number: 9720599

  Abstract: A magnetic system for solving a quadratic optimization problem by associating each of a plurality of variables of a quadratic optimization problem with a nanomagnet of a nanomagnet array, driving the nanomagnets of the nanomagnet array to an excited state, allowing the nanomagnets of the nanomagnet array to enter a relaxed state after being driven to an excited state, wherein the nanomagnets magnetically couple with one another in the relaxed state to minimize the total magnetic coupling energy of the nanomagnet array, and sensing a magnetic coupling of the nanomagnets of the nanomagnet array to solve the quadratic optimization problem.

  Type: Grant

  Filed: June 24, 2016

  Date of Patent: August 1, 2017

  Assignee: University of South Florida

  Inventors: Sanjukta Bhanja, Sudeep Sarkar, Ravi Panchumarthy, Dinuka K. Karunaratne

• MAGNETIC MEMORY PHYSICALLY UNCLONABLE FUNCTIONS

  Publication number: 20170214532

  Abstract: A magnetic random access memory (MRAM) physically unclonable function (PUF) device that uses the geometric variations in magnetic memory cells to generate a random PUF response is described herein. Within the MRAM, one or more magnetic memory cells can be used for the PUF. The PUF response is generated by destabilizing the one or more magnetic memory cells and then allowing them to relax. The MRAM PUF has also a relatively small foot-print among all other silicon PUFs. Timing and control signals for the MRAM PUF are also described along with power and delay characteristics for use with with field and spin transfer torque driven destabilization operations.

  Type: Application

  Filed: May 28, 2015

  Publication date: July 27, 2017

  Applicant: University of South Florida

  Inventors: JAYITA DAS, KEVIN P. SCOTT, DREW H. BURGETT, SRINATH RAJARAM, SANJUKTA BHANJA

• MAGNETIC COPROCESSOR AND METHOD OF USE

  Publication number: 20170060417

  Abstract: A magnetic system for solving a quadratic optimization problem by associating each of a plurality of variables of a quadratic optimization problem with a nanomagnet of a nanomagnet array, driving the nanomagnets of the nanomagnet array to an excited state, allowing the nanomagnets of the nanomagnet array to enter a relaxed state after being driven to an excited state, wherein the nanomagnets magnetically couple with one another in the relaxed state to minimize the total magnetic coupling energy of the nanomagnet array, and sensing a magnetic coupling of the nanomagnets of the nanomagnet array to solve the quadratic optimization problem.

  Type: Application

  Filed: June 24, 2016

  Publication date: March 2, 2017

  Applicant: University of South Florida

  Inventors: Sanjukta Bhanja, Sudeep Sarkar, Ravi Panchumarthy, Dinuka K. Karunaratne

• MATERIALS AND METHODS FOR DETECTING AND MONITORING EDEMA AND RELATED CONDITIONS

  Publication number: 20160331314

  Abstract: The subject invention provides a Coupled Domain Sensor (CDS) that can be used to, for example, evaluate hydration and occlusion of blood in patients with edema using electrical and optical measurements. Advantageously, the CDS provides a quicker, more effective and accurate way of monitoring this medical condition.

  Type: Application

  Filed: May 16, 2016

  Publication date: November 17, 2016

  Applicants: The Florida International University Board of Trustees, University of South Florida

  Inventors: Shekhar BHANSALI, Karina RINCON, Jessica RAMELLA-ROMAN, Sanjukta BHANJA

• System and method for estimating the magnetization states of a nanomagnet array

  Patent number: 9286687

  Abstract: A system and method for image-processing that will facilitate automatically analyzing and estimating atomic force microscopy (AFM) images and magnetic force microscopy (MFM) images of fabricated nanomagnetic arrays to identify the magnetization states of the nanomagnets in the array. The system and method will automatically estimate the magnetization states of nanomagnetics disks into one of a plurality of energy minimum magnetization state configurations and provide an annotated image of the results of the estimation.

  Type: Grant

  Filed: August 25, 2014

  Date of Patent: March 15, 2016

  Assignee: University of South Florida

  Inventors: Ravi Panchumarthy, Dinuka K. Karunaratne, Sudeep Sarkar, Sanjukta Bhanja

MatlabHTM: A sequence memory model of neocortical layers for anomaly detection

Bautista, I., Sarkar, S., & Bhanja, S. (2020). MatlabHTM: A sequence memory model of neocortical layers for anomaly detection. SoftwareX, 11, 100491.

Abstract

Many models based on the operation of the neocortex, which is the center of brain intelligence, are emerging. The Hierarchical Temporal Memory (HTM) model is a unique intermediate level model of the neocortex’s layered substructures. The hypothesis is that these layers build temporal models of sequences of observations and/or motor signals, i.e., build a sequence memory. Implementations of this model exist in Python, C++ and Java. However, those implementations are quite cumbersome to use, as they depend on many other packages. This paper presents a lean, standalone, easy to modify MATLAB implementation. The performance results from processing the Numenta Anomaly Benchmark (NAB) demonstrate the fidelity of matlabHTM.

Spin–Orbit Torque and Dipole Coupling for Nanomagnetic Array Programmability

Nance, J. A., Roxy, K. A., Bhanja, S., & Carman, G. P. (2020). Spin-Orbit Torque and Dipole Coupling for Nanomagnetic Array Programmability. IEEE Transactions on Magnetics.

Abstract: Computational architectures that rely on an array of dipole-coupled nanomagnetic elements require an energy-efficient method of programming individual elements within the array. As a low-energy, selective method of controlling magnetization, spin–orbit torque (SOT) represents a promising solution. Here, a finite-difference micromagnetic model is used to characterize the dipole coupling between adjacent CoFeB nanodisks and to determine the critical SOT current required to switch these disks. Additionally, a phase plot showing disk dimensions at which both vortex and single-domain in-plane magnetic states are stable is produced. A dipole-coupled array’s response to dynamic application of SOT current is also simulated. The results show that the rate of applying SOT current to one element in the array strongly influences the stable states of adjacent elements and that the SOT current amplitude required for this influence is an order of magnitude lower than the previously determined critical switching current. This indicates that SOT current dynamics play a significant role in the behavior of a dipole-coupled array. Finally, an architecture to achieve programmability in nanomagnetic computational platforms with SOT is presented. 

Spin–Orbit Torque and Dipole Coupling for Nanomagnetic Array Programmability

 Nance, John A., Kawsher A. Roxy, Sanjukta Bhanja, and Greg P. Carman. "Spin–Orbit Torque and Dipole Coupling for Nanomagnetic Array Programmability." IEEE Transactions on Magnetics 56, no. 7 (2020): 1-8.

 Keywords:

• Array programmability ,
• dipole coupling ,
• spin–orbit torque (SOT) ,
• spintronics

Abstract:

Computational architectures that rely on an array of dipole-coupled nanomagnetic elements require an energy-efficient method of programming individual elements within the array. As a low-energy, selective method of controlling magnetization, spin-orbit torque (SOT) represents a promising solution. Here, a finite-difference micromagnetic model is used to characterize the dipole coupling between adjacent CoFeB nanodisks and to determine the critical SOT current required to switch these disks. Additionally, a phase plot showing disk dimensions at which both vortex and single-domain in-plane magnetic states are stable is produced. A dipole-coupled array's response to dynamic application of SOT current is also simulated. The results show that the rate of applying SOT current to one element in the array strongly influences the stable states of adjacent elements and that the SOT current amplitude required for this influence is an order of magnitude lower than the previously determined critical switching current. This indicates that SOT current dynamics play a significant role in the behavior of a dipole-coupled array. Finally, an architecture to achieve programmability in nanomagnetic computational platforms with SOT is presented.

 

@ARTICLE{9095323,
  author={Nance, John A. and Roxy, Kawsher A. and Bhanja, Sanjukta and Carman, Greg P.},
  journal={IEEE Transactions on Magnetics}, 
  title={Spin–Orbit Torque and Dipole Coupling for Nanomagnetic Array Programmability}, 
  year={2020},
  volume={56},
  number={7},
  pages={1-8},
  doi={10.1109/TMAG.2020.2995514}}