## Tunnel Junction

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### Hideo Ohno - One of the best experts on this subject based on the ideXlab platform.

• ##### magnetization switching in a cofeb mgo magnetic Tunnel Junction by combining spin transfer torque and electric field effect
Applied Physics Letters, 2014
Co-Authors: Shun Kanai, Shoji Ikeda, H Sato, M Yamanouchi, F Matsukura, Yoshinobu Nakatani, Hideo Ohno
Abstract:

We propose and demonstrate a scheme for magnetization switching in magnetic Tunnel Junctions, in which two successive voltage pulses are applied to utilize both spin-transfer torque and electric field effect. Under this switching scheme, a CoFeB/MgO magnetic Tunnel Junction with perpendicular magnetic easy axis is shown to switch faster than by spin-transfer torque alone and more reliably than that by electric fields alone.

• ##### comprehensive study of cofeb mgo magnetic Tunnel Junction characteristics with single and double interface scaling down to 1x nm
International Electron Devices Meeting, 2013
Co-Authors: H Sato, Shoji Ikeda, Naoki Kasai, T Yamamoto, M Yamanouchi, Shunsuke Fukami, Keizo Kinoshita, F Matsukura, Hideo Ohno
Abstract:

We study characteristics of CoFeB-MgO magnetic Tunnel Junction with perpendicular easy-axis (p-MTJ) at a reduced dimension down to 1X nm fabricated by hard-mask process. CoFeB-MgO p-MTJ with double-interface shows higher thermal stability down to 1X nm than that with single-interface. Thermal stability factor of 58 and intrinsic critical current of 24 μA are obtained in the CoFeB-MgO magnetic Tunnel Junction with perpendicular easy-axis using double-interface structure at a diameter of 20 nmφ.

• ##### three terminal magnetic Tunnel Junction utilizing the spin hall effect of iridium doped copper
Applied Physics Letters, 2013
Co-Authors: M Yamanouchi, Shoji Ikeda, H Sato, Shunsuke Fukami, F Matsukura, Lin Chen, J Kim, Masamitsu Hayashi, Hideo Ohno
Abstract:

We show a three terminal magnetic Tunnel Junction (MTJ) with a 10-nm thick channel based on an interconnection material Cu with 10% Ir doping. By applying a current density of less than 1012 A m−2 to the channel, depending on the current direction, switching of a MTJ defined on the channel takes place. We show that spin transfer torque (STT) plays a critical role in determining the threshold current. By assuming the spin Hall effect in the channel being the source of the STT, the lower bound of magnitude of the spin Hall angle is evaluated to be 0.03.

• ##### magnetic Tunnel Junction for nonvolatile cmos logic
International Electron Devices Meeting, 2010
Co-Authors: Hideo Ohno, Tetsuo Endoh, Takahiro Hanyu, Naoki Kasai, Shoji Ikeda
Abstract:

Magnetic Tunnel Junction (MTJ) device, a nonvolatile spintronic device, is capable of fast-read/write with high endurance together with back-end-of-the-line (BEOL) compatibility, offering a possibility of constructing not only stand-alone RAMs and embedded RAMs that can be used in conventional VLSI circuits and systems but also low-power high-performance nonvolatile CMOS logic employing logic-in-memory architecture. The advantages of employing MTJs with CMOS circuits are discussed and the current status of the MTJ technology is presented along with its prospect and remaining challenges.

### Kaushik Roy - One of the best experts on this subject based on the ideXlab platform.

• ##### Magnetic Tunnel Junction as an On-Chip Temperature Sensor.
Scientific Reports, 2017
Co-Authors: Abhronil Sengupta, Chamika M. Liyanagedera, Byunghoo Jung, Kaushik Roy
Abstract:

Temperature sensors are becoming an increasingly important component in System-on-Chip (SoC) designs with increasing transistor scaling, power density and associated heating effects. This work explores a compact nanoelectronic temperature sensor based on a Magnetic Tunnel Junction (MTJ) structure. The MTJ switches probabilistically depending on the operating temperature in the presence of thermal noise. Performance evaluation of the proposed MTJ temperature sensor, based on experimentally measured device parameters, reveals that the sensor is able to achieve a conversion rate of 2.5K samples/s with energy consumption of 8.8 nJ per conversion (1-2 orders of magnitude lower than state-of-the-art CMOS sensors) for a linear sensing regime of 200-400 K.

• ##### Magnetic Tunnel Junction Mimics Stochastic Cortical Spiking Neurons
Scientific Reports, 2016
Co-Authors: Abhronil Sengupta, Priyadarshini Panda, Parami Wijesinghe, Yusung Kim, Kaushik Roy
Abstract:

Brain-inspired computing architectures attempt to mimic the computations performed in the neurons and the synapses in the human brain in order to achieve its efficiency in learning and cognitive tasks. In this work, we demonstrate the mapping of the probabilistic spiking nature of pyramidal neurons in the cortex to the stochastic switching behavior of a Magnetic Tunnel Junction in presence of thermal noise. We present results to illustrate the efficiency of neuromorphic systems based on such probabilistic neurons for pattern recognition tasks in presence of lateral inhibition and homeostasis. Such stochastic MTJ neurons can also potentially provide a direct mapping to the probabilistic computing elements in Belief Networks for performing regenerative tasks.

• ##### probabilistic deep spiking neural systems enabled by magnetic Tunnel Junction
IEEE Transactions on Electron Devices, 2016
Co-Authors: Abhronil Sengupta, Maryam Parsa, Bing Han, Kaushik Roy
Abstract:

Deep spiking neural networks are becoming increasingly powerful tools for cognitive computing platforms. However, most of the existing studies on such computing models are developed with limited insights on the underlying hardware implementation, resulting in area and power expensive designs. Although several neuromimetic devices emulating neural operations have been proposed recently, their functionality has been limited to very simple neural models that may prove to be inefficient at complex recognition tasks. In this paper, we venture into the relatively unexplored area of utilizing the inherent device stochasticity of such neuromimetic devices to model complex neural functionalities in a probabilistic framework in the time domain. We consider the implementation of a deep spiking neural network capable of performing high-accuracy and low-latency classification tasks, where the neural computing unit is enabled by the stochastic switching behavior of a magnetic Tunnel Junction. The simulation studies indicate an energy improvement of $20 \times$ over a baseline CMOS design in 45-nm technology.

• ##### probabilistic deep spiking neural systems enabled by magnetic Tunnel Junction
arXiv: Emerging Technologies, 2016
Co-Authors: Abhronil Sengupta, Maryam Parsa, Bing Han, Kaushik Roy
Abstract:

Deep Spiking Neural Networks are becoming increasingly powerful tools for cognitive computing platforms. However, most of the existing literature on such computing models are developed with limited insights on the underlying hardware implementation, resulting in area and power expensive designs. Although several neuromimetic devices emulating neural operations have been proposed recently, their functionality has been limited to very simple neural models that may prove to be inefficient at complex recognition tasks. In this work, we venture into the relatively unexplored area of utilizing the inherent device stochasticity of such neuromimetic devices to model complex neural functionalities in a probabilistic framework in the time domain. We consider the implementation of a Deep Spiking Neural Network capable of performing high accuracy and low latency classification tasks where the neural computing unit is enabled by the stochastic switching behavior of a Magnetic Tunnel Junction. Simulation studies indicate an energy improvement of $20\times$ over a baseline CMOS design in $45nm$ technology.

### Shoji Ikeda - One of the best experts on this subject based on the ideXlab platform.

• ##### magnetization switching in a cofeb mgo magnetic Tunnel Junction by combining spin transfer torque and electric field effect
Applied Physics Letters, 2014
Co-Authors: Shun Kanai, Shoji Ikeda, H Sato, M Yamanouchi, F Matsukura, Yoshinobu Nakatani, Hideo Ohno
Abstract:

We propose and demonstrate a scheme for magnetization switching in magnetic Tunnel Junctions, in which two successive voltage pulses are applied to utilize both spin-transfer torque and electric field effect. Under this switching scheme, a CoFeB/MgO magnetic Tunnel Junction with perpendicular magnetic easy axis is shown to switch faster than by spin-transfer torque alone and more reliably than that by electric fields alone.

• ##### comprehensive study of cofeb mgo magnetic Tunnel Junction characteristics with single and double interface scaling down to 1x nm
International Electron Devices Meeting, 2013
Co-Authors: H Sato, Shoji Ikeda, Naoki Kasai, T Yamamoto, M Yamanouchi, Shunsuke Fukami, Keizo Kinoshita, F Matsukura, Hideo Ohno
Abstract:

We study characteristics of CoFeB-MgO magnetic Tunnel Junction with perpendicular easy-axis (p-MTJ) at a reduced dimension down to 1X nm fabricated by hard-mask process. CoFeB-MgO p-MTJ with double-interface shows higher thermal stability down to 1X nm than that with single-interface. Thermal stability factor of 58 and intrinsic critical current of 24 μA are obtained in the CoFeB-MgO magnetic Tunnel Junction with perpendicular easy-axis using double-interface structure at a diameter of 20 nmφ.

• ##### three terminal magnetic Tunnel Junction utilizing the spin hall effect of iridium doped copper
Applied Physics Letters, 2013
Co-Authors: M Yamanouchi, Shoji Ikeda, H Sato, Shunsuke Fukami, F Matsukura, Lin Chen, J Kim, Masamitsu Hayashi, Hideo Ohno
Abstract:

We show a three terminal magnetic Tunnel Junction (MTJ) with a 10-nm thick channel based on an interconnection material Cu with 10% Ir doping. By applying a current density of less than 1012 A m−2 to the channel, depending on the current direction, switching of a MTJ defined on the channel takes place. We show that spin transfer torque (STT) plays a critical role in determining the threshold current. By assuming the spin Hall effect in the channel being the source of the STT, the lower bound of magnitude of the spin Hall angle is evaluated to be 0.03.

• ##### magnetic Tunnel Junction for nonvolatile cmos logic
International Electron Devices Meeting, 2010
Co-Authors: Hideo Ohno, Tetsuo Endoh, Takahiro Hanyu, Naoki Kasai, Shoji Ikeda
Abstract:

Magnetic Tunnel Junction (MTJ) device, a nonvolatile spintronic device, is capable of fast-read/write with high endurance together with back-end-of-the-line (BEOL) compatibility, offering a possibility of constructing not only stand-alone RAMs and embedded RAMs that can be used in conventional VLSI circuits and systems but also low-power high-performance nonvolatile CMOS logic employing logic-in-memory architecture. The advantages of employing MTJs with CMOS circuits are discussed and the current status of the MTJ technology is presented along with its prospect and remaining challenges.

• ##### a perpendicular anisotropy cofeb mgo magnetic Tunnel Junction
Nature Materials, 2010
Co-Authors: Shoji Ikeda, K Miura, Hiroyuki Yamamoto, K Mizunuma, Huadong Gan, M Endo, Shun Kanai, Jun Hayakawa
Abstract:

Materials with perpendicular anisotropy receive considerable attention owing to their potential in being employed in efficient memory devices. It is now shown that a type of magnetic Tunnel Junction widely studied for in-plane magnetic anisotropy has all the properties necessary to realize stable and efficient devices based on perpendicular magnetic anisotropy.

### Gilles Gaudin - One of the best experts on this subject based on the ideXlab platform.

• ##### Spin-orbit torque magnetization switching of a three-terminal perpendicular magnetic Tunnel Junction
Applied Physics Letters, 2014
Co-Authors: M. Cubukcu, Berthold Ocker, Olivier Boulle, Marc Drouard, Kevin Garello, Can Onur Avci, Ioan Mihai Miron, Juergen Langer, Pietro Gambardella, Gilles Gaudin
Abstract:

We report on the current-induced magnetization switching of a three-terminal perpendicular magnetic Tunnel Junction by spin-orbit torque and its read-out using the Tunnelling magnetoresistance (TMR) effect. The device is composed of a perpendicular Ta/FeCoB/MgO/FeCoB stack on top of a Ta current line. The magnetization of the bottom FeCoB layer can be switched reproducibly by the injection of current pulses with density 5 × 1011 A/m2 in the Ta layer in the presence of an in-plane bias magnetic field, leading to the full-scale change of the TMR signal. Our work demonstrates the proof of concept of a perpendicular spin-orbit torque magnetic memory cell.

• ##### spin orbit torque magnetization switching of a three terminal perpendicular magnetic Tunnel Junction
arXiv: Materials Science, 2013
Co-Authors: M. Cubukcu, Berthold Ocker, Olivier Boulle, Marc Drouard, Kevin Garello, Can Onur Avci, Ioan Mihai Miron, Juergen Langer, Pietro Gambardella, Gilles Gaudin
Abstract:

We report on the current-induced magnetization switching of a three-terminal perpendicular magnetic Tunnel Junction by spin-orbit torque and the read-out using the Tunnelling magnetoresistance (TMR) effect. The device is composed of a perpendicular Ta/FeCoB/MgO/FeCoB stack on top of a Ta current line. The magnetization of the bottom FeCoB layer can be switched reproducibly by the injection of current pulses with density $5\times10^{11}$ A/m$^2$ in the Ta layer in the presence of an in-plane bias magnetic field, leading to the full-scale change of the TMR signal. Our work demonstrates the proof of concept of a perpendicular spin-orbit torque magnetic memory cell.

### Berthold Ocker - One of the best experts on this subject based on the ideXlab platform.

• ##### Spin-orbit torque magnetization switching of a three-terminal perpendicular magnetic Tunnel Junction
Applied Physics Letters, 2014
Co-Authors: M. Cubukcu, Berthold Ocker, Olivier Boulle, Marc Drouard, Kevin Garello, Can Onur Avci, Ioan Mihai Miron, Juergen Langer, Pietro Gambardella, Gilles Gaudin
Abstract:

We report on the current-induced magnetization switching of a three-terminal perpendicular magnetic Tunnel Junction by spin-orbit torque and its read-out using the Tunnelling magnetoresistance (TMR) effect. The device is composed of a perpendicular Ta/FeCoB/MgO/FeCoB stack on top of a Ta current line. The magnetization of the bottom FeCoB layer can be switched reproducibly by the injection of current pulses with density 5 × 1011 A/m2 in the Ta layer in the presence of an in-plane bias magnetic field, leading to the full-scale change of the TMR signal. Our work demonstrates the proof of concept of a perpendicular spin-orbit torque magnetic memory cell.

• ##### spin orbit torque magnetization switching of a three terminal perpendicular magnetic Tunnel Junction
arXiv: Materials Science, 2013
Co-Authors: M. Cubukcu, Berthold Ocker, Olivier Boulle, Marc Drouard, Kevin Garello, Can Onur Avci, Ioan Mihai Miron, Juergen Langer, Pietro Gambardella, Gilles Gaudin
Abstract:

We report on the current-induced magnetization switching of a three-terminal perpendicular magnetic Tunnel Junction by spin-orbit torque and the read-out using the Tunnelling magnetoresistance (TMR) effect. The device is composed of a perpendicular Ta/FeCoB/MgO/FeCoB stack on top of a Ta current line. The magnetization of the bottom FeCoB layer can be switched reproducibly by the injection of current pulses with density $5\times10^{11}$ A/m$^2$ in the Ta layer in the presence of an in-plane bias magnetic field, leading to the full-scale change of the TMR signal. Our work demonstrates the proof of concept of a perpendicular spin-orbit torque magnetic memory cell.

• ##### Tunneling magnetothermopower in magnetic Tunnel Junction nanopillars
Physical Review Letters, 2011
Co-Authors: N Liebing, S Serranoguisan, Karsten Rott, Gunter Reiss, J Langer, Berthold Ocker, H W Schumacher
Abstract:

We study Tunneling magnetothermopower (TMTP) in CoFeB/MgO/CoFeB magnetic Tunnel Junction nanopillars. Thermal gradients across the Junctions are generated by an electric heater line. Thermopower voltages up to a few tens of μV between the top and bottom contact of the nanopillars are measured which scale linearly with the applied heating power and hence the thermal gradient. The thermopower signal varies by up to 10  μV upon reversal of the relative magnetic configuration of the two CoFeB layers from parallel to antiparallel. This signal change corresponds to a large spin-dependent Seebeck coefficient of the order of 100  μV/K and a large TMTP change of the Tunnel Junction of up to 90%.