1
|
Chen X, Araujo FA, Riou M, Torrejon J, Ravelosona D, Kang W, Zhao W, Grollier J, Querlioz D. Forecasting the outcome of spintronic experiments with Neural Ordinary Differential Equations. Nat Commun 2022; 13:1016. [PMID: 35197449 PMCID: PMC8866480 DOI: 10.1038/s41467-022-28571-7] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2021] [Accepted: 01/19/2022] [Indexed: 11/09/2022] Open
Abstract
Deep learning has an increasing impact to assist research, allowing, for example, the discovery of novel materials. Until now, however, these artificial intelligence techniques have fallen short of discovering the full differential equation of an experimental physical system. Here we show that a dynamical neural network, trained on a minimal amount of data, can predict the behavior of spintronic devices with high accuracy and an extremely efficient simulation time, compared to the micromagnetic simulations that are usually employed to model them. For this purpose, we re-frame the formalism of Neural Ordinary Differential Equations to the constraints of spintronics: few measured outputs, multiple inputs and internal parameters. We demonstrate with Neural Ordinary Differential Equations an acceleration factor over 200 compared to micromagnetic simulations for a complex problem - the simulation of a reservoir computer made of magnetic skyrmions (20 minutes compared to three days). In a second realization, we show that we can predict the noisy response of experimental spintronic nano-oscillators to varying inputs after training Neural Ordinary Differential Equations on five milliseconds of their measured response to a different set of inputs. Neural Ordinary Differential Equations can therefore constitute a disruptive tool for developing spintronic applications in complement to micromagnetic simulations, which are time-consuming and cannot fit experiments when noise or imperfections are present. Our approach can also be generalized to other electronic devices involving dynamics.
Collapse
Affiliation(s)
- Xing Chen
- Fert Beijing Institute, MIIT Key Laboratory of Spintronics, School of Integrated Circuit Science and Engineering, Beihang University, 100191, Beijing, China.,Université Paris-Saclay, CNRS, Centre de Nanosciences et de Nanotechnologies, Palaiseau, France
| | - Flavio Abreu Araujo
- Institute of Condensed Matter and Nanosciences, Université catholique de Louvain, Place Croix du Sud 1, Louvain-la-Neuve, 1348, Belgium.,Unité Mixte de Physique, CNRS, Thales, Université Paris-Saclay, Palaiseau, France
| | - Mathieu Riou
- Unité Mixte de Physique, CNRS, Thales, Université Paris-Saclay, Palaiseau, France
| | - Jacob Torrejon
- Unité Mixte de Physique, CNRS, Thales, Université Paris-Saclay, Palaiseau, France
| | - Dafiné Ravelosona
- Université Paris-Saclay, CNRS, Centre de Nanosciences et de Nanotechnologies, Palaiseau, France
| | - Wang Kang
- Fert Beijing Institute, MIIT Key Laboratory of Spintronics, School of Integrated Circuit Science and Engineering, Beihang University, 100191, Beijing, China
| | - Weisheng Zhao
- Fert Beijing Institute, MIIT Key Laboratory of Spintronics, School of Integrated Circuit Science and Engineering, Beihang University, 100191, Beijing, China
| | - Julie Grollier
- Unité Mixte de Physique, CNRS, Thales, Université Paris-Saclay, Palaiseau, France
| | - Damien Querlioz
- Université Paris-Saclay, CNRS, Centre de Nanosciences et de Nanotechnologies, Palaiseau, France.
| |
Collapse
|
2
|
Rana B, Miura K, Takahashi H, Otani Y. Underlayer material dependent symmetric and asymmetric behavior of voltage-controlled magnetic anisotropy in CoFeB films. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2020; 32:414002. [PMID: 32503010 DOI: 10.1088/1361-648x/ab99eb] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/04/2020] [Accepted: 06/05/2020] [Indexed: 06/11/2023]
Abstract
Voltage-controlled magnetic anisotropy (VCMA), observed at the interfaces of ultrathin ferromagnetic metallic films and oxide layer, has proven to be a useful tool for the development of all-electric field controlled spintronics devices. Here, we have studied the symmetric and asymmetric behavior of VCMA in CoFeB/MgO heterostructures, grown on different underlayer materials, by measuring ferromagnetic resonance using spin pumping and inverse spin Hall effect technique. We observe symmetric behavior of VCMA in CoFeB films with Ta underlayer, whereas a systematic transformation from symmetric to asymmetric behavior of VCMA with decreasing CoFeB thickness is observed for Pt underlayer. We speculate that the increased interfacial roughness, defects and strain of ultrathin CoFeB films with Pt buffer layer probably leads to the complicated band structure at CoFeB/MgO interface resulting in asymmetric behavior of VCMA. The observed symmetric behavior of VCMA in control samples justifies the role of interfacial roughness, defects and discards the role of oxide overlayer on the observed asymmetric behavior of VCMA in ultrathin CoFeB films.
Collapse
Affiliation(s)
- Bivas Rana
- Center for Emergent Matter Science, RIKEN, 2-1 Hirosawa, Wako 351-0198, Japan
| | - Katsuya Miura
- Research and Development Group, Hitachi, Ltd., 1-280 Higashi-koigakubo, Kokubunji-shi, Tokyo 185-8601, Japan
| | - Hiromasa Takahashi
- Research and Development Group, Hitachi, Ltd., 1-280 Higashi-koigakubo, Kokubunji-shi, Tokyo 185-8601, Japan
| | - YoshiChika Otani
- Center for Emergent Matter Science, RIKEN, 2-1 Hirosawa, Wako 351-0198, Japan
- Institute for Solid State Physics, University of Tokyo, Kashiwa 277-8581, Japan
| |
Collapse
|
3
|
Nozaki T, Yamamoto T, Miwa S, Tsujikawa M, Shirai M, Yuasa S, Suzuki Y. Recent Progress in the Voltage-Controlled Magnetic Anisotropy Effect and the Challenges Faced in Developing Voltage-Torque MRAM. MICROMACHINES 2019; 10:E327. [PMID: 31096668 PMCID: PMC6562605 DOI: 10.3390/mi10050327] [Citation(s) in RCA: 60] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/24/2019] [Revised: 05/10/2019] [Accepted: 05/12/2019] [Indexed: 12/04/2022]
Abstract
The electron spin degree of freedom can provide the functionality of "nonvolatility" in electronic devices. For example, magnetoresistive random access memory (MRAM) is expected as an ideal nonvolatile working memory, with high speed response, high write endurance, and good compatibility with complementary metal-oxide-semiconductor (CMOS) technologies. However, a challenging technical issue is to reduce the operating power. With the present technology, an electrical current is required to control the direction and dynamics of the spin. This consumes high energy when compared with electric-field controlled devices, such as those that are used in the semiconductor industry. A novel approach to overcome this problem is to use the voltage-controlled magnetic anisotropy (VCMA) effect, which draws attention to the development of a new type of MRAM that is controlled by voltage (voltage-torque MRAM). This paper reviews recent progress in experimental demonstrations of the VCMA effect. First, we present an overview of the early experimental observations of the VCMA effect in all-solid state devices, and follow this with an introduction of the concept of the voltage-induced dynamic switching technique. Subsequently, we describe recent progress in understanding of physical origin of the VCMA effect. Finally, new materials research to realize a highly-efficient VCMA effect and the verification of reliable voltage-induced dynamic switching with a low write error rate are introduced, followed by a discussion of the technical challenges that will be encountered in the future development of voltage-torque MRAM.
Collapse
Affiliation(s)
- Takayuki Nozaki
- National Institute of Advanced Industrial Science and Technology (AIST), Spintronics Research Center, Tsukuba, Ibaraki 305-8568, Japan.
| | - Tatsuya Yamamoto
- National Institute of Advanced Industrial Science and Technology (AIST), Spintronics Research Center, Tsukuba, Ibaraki 305-8568, Japan.
| | - Shinji Miwa
- The Institute of Solid State Physics, The University of Tokyo, Kashiwa, Chiba 277-8531, Japan.
- Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka 560-8531, Japan.
| | - Masahito Tsujikawa
- Research Institute of Electrical Communication, Tohoku University, Sendai, Miyagi 980-8577, Japan.
| | - Masafumi Shirai
- Research Institute of Electrical Communication, Tohoku University, Sendai, Miyagi 980-8577, Japan.
| | - Shinji Yuasa
- National Institute of Advanced Industrial Science and Technology (AIST), Spintronics Research Center, Tsukuba, Ibaraki 305-8568, Japan.
| | - Yoshishige Suzuki
- National Institute of Advanced Industrial Science and Technology (AIST), Spintronics Research Center, Tsukuba, Ibaraki 305-8568, Japan.
- Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka 560-8531, Japan.
| |
Collapse
|
4
|
High velocity domain wall propagation using voltage controlled magnetic anisotropy. Sci Rep 2019; 9:7369. [PMID: 31089209 PMCID: PMC6517393 DOI: 10.1038/s41598-019-43843-x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2018] [Accepted: 04/27/2019] [Indexed: 11/08/2022] Open
Abstract
The use of voltage-controlled magnetic anisotropy (VCMA) via the creation of a sloped electric field has been hailed as an energy-efficient approach for domain wall (DW) propagation. However, this method suffers from a limitation of the nanowire length which the DW can propagate on. Here, we propose the use of multiplexed gate electrodes to propagate DWs on magnetic nanowires without having any length constraints. The multi-gate electrode configuration is demonstrated using micromagnetic simulations. This allows controllable voltages to be applied to neighboring gate electrodes, generating large strength of magnetic anisotropy gradients along the nanowire, and the results show that DW velocities higher than 300 m/s can be achieved. Analysis of the DW dynamics during propagation reveals that the tilt of the DW and the direction of slanted gate electrode greatly alters the steady state DW propagation. Our results show that chevron-shaped gate electrodes is an effective optimisation that leads to multi-DW propagation with high velocity. Moreover, a repeating series of high-medium-low magnetic anisotropy regions enables a deterministic VCMA-controlled high velocity DW propagation.
Collapse
|
5
|
Goto M, Wakatake Y, Oji UK, Miwa S, Strelkov N, Dieny B, Kubota H, Yakushiji K, Fukushima A, Yuasa S, Suzuki Y. Microwave amplification in a magnetic tunnel junction induced by heat-to-spin conversion at the nanoscale. NATURE NANOTECHNOLOGY 2019; 14:40-43. [PMID: 30478277 DOI: 10.1038/s41565-018-0306-9] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/30/2018] [Accepted: 10/18/2018] [Indexed: 06/09/2023]
Abstract
Heat-driven engines are hard to realize in nanoscale machines because of efficient heat dissipation1. However, in the realm of spintronics, heat has been employed successfully-for example, heat current has been converted into a spin current in a NiFe|Pt bilayer system2, and Joule heating has enabled selective writing in magnetic memory arrays3. Here, we use Joule heating in nanoscale magnetic tunnel junctions to create a giant spin torque due to a magnetic anisotropy change. Efficient conversion from heat dynamics to spin dynamics is obtained because of a large interfacial thermal resistance at an FeB|MgO interface. The heat-driven spin torque is equivalent to a voltage-controlled magnetic anisotropy4,5 of approximately 300 fJ V-1 m-1, which is more than twice the value reported in a (Co)FeB|MgO system6,7. We demonstrate an electric microwave amplification gain of 20% in a d.c. biased magnetic tunnel junction as a result of this spin torque. While electric d.c. power amplification in spintronic devices has been realized previously8, the microwave amplification was limited to relatively small amplification gains (G = radiofrequency output voltage/radiofrequency input voltage) and has never exceeded 1 (refs 9-13). A magnetic tunnel junction driven by radiofrequency spin transfer torque using ferromagnetic resonance enabled a relatively large gain of G ≈ 0.55 (ref. 12). Furthermore, radiofrequency spin waves were tuned by the spin transfer effect14,15. The heat-driven giant spin torque in the FeB|MgO16,17 magnetic tunnel junction, which shows a large magnetization precession and resistance oscillation under a d.c. bias, overcomes the above limitations and provides a gain larger than 1.
Collapse
Affiliation(s)
- Minori Goto
- Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka, Japan
- Center for Spintronics Research Network (CSRN), Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka, Japan
| | - Yosuke Wakatake
- Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka, Japan
| | | | - Shinji Miwa
- Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka, Japan
- Center for Spintronics Research Network (CSRN), Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka, Japan
- The Institute for Solid State Physics, The University of Tokyo, Kashiwa, Chiba, Japan
| | - Nikita Strelkov
- Grenoble Alpes University, CEA, CNRS, Grenoble INP, INAC, SPINTEC, Grenoble, France
- Department of Physics, Moscow Lomonosov State University, Moscow, Russia
| | - Bernard Dieny
- Grenoble Alpes University, CEA, CNRS, Grenoble INP, INAC, SPINTEC, Grenoble, France
| | - Hitoshi Kubota
- National Institute of Advanced Industrial Science and Technology (AIST), Spintronics Research Center, Tsukuba, Ibaraki, Japan
| | - Kay Yakushiji
- National Institute of Advanced Industrial Science and Technology (AIST), Spintronics Research Center, Tsukuba, Ibaraki, Japan
| | - Akio Fukushima
- National Institute of Advanced Industrial Science and Technology (AIST), Spintronics Research Center, Tsukuba, Ibaraki, Japan
| | - Shinji Yuasa
- National Institute of Advanced Industrial Science and Technology (AIST), Spintronics Research Center, Tsukuba, Ibaraki, Japan
| | - Yoshishige Suzuki
- Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka, Japan.
- Center for Spintronics Research Network (CSRN), Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka, Japan.
| |
Collapse
|
6
|
Voltage-Controlled Magnetic Anisotropy in Fe 1-xCo x/Pd/MgO system. Sci Rep 2018; 8:10362. [PMID: 29985395 PMCID: PMC6037784 DOI: 10.1038/s41598-018-28445-3] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2018] [Accepted: 06/22/2018] [Indexed: 11/18/2022] Open
Abstract
Voltage-controlled magnetic anisotropy (VCMA) in an epitaxially grown Fe/Fe1−xCox/Pd/MgO system was investigated using spin-wave spectroscopy. The spin-wave resonant frequency linearly depended on the bias-voltage. The resonant-frequency shift increased with the Co fraction in Fe1−xCox/Pd. We achieved a VCMA of approximately 250 fJ/Vm at the Co/Pd/MgO region.
Collapse
|