Article
Chemistry, Multidisciplinary
Alejandro Schulman, Elvira Paz, Tim Bohnert, Alex Steven Jenkins, Ricardo Ferreira
Summary: Magnetic tunnel junctions (MTJs) and memristors are emerging nanotechnologies that have attracted significant attention for their potential applications in sensing, data storage, and computation. This study demonstrates the co-existence of magnetoresistance and memristive properties on MTJs, showing potential for multifunctional devices. Furthermore, doping the oxide barrier lowers the power consumption of the memristive behavior, enhancing the scalability potential. These findings pave the way for integrating memristors and spintronic devices in complex reprogrammable circuits.
ADVANCED FUNCTIONAL MATERIALS
(2023)
Article
Multidisciplinary Sciences
Suyogya Karki, Vivian Rogers, Priyamvada Jadaun, Daniel S. Marshall, Jean Anne C. Incorvia
Summary: The study suggests that scandium nitride could be a potential barrier material for spintronic devices, as it shows high magnetoresistance compared to magnesium oxide.
ADVANCED THEORY AND SIMULATIONS
(2021)
Article
Nanoscience & Nanotechnology
Trevor P. Almeida, Alvaro Palomino, Steven Lequeux, Victor Boureau, Olivier Fruchart, Ioan Lucian Prejbeanu, Bernard Dieny, David Cooper
Summary: This paper reviews recent work on perpendicular shape anisotropy and double magnetic tunnel junctions using advanced electron microscopy techniques, with a focus on the 3D and nanoscale nature of these structures. By directly imaging the magnetic configurations using off-axis electron holography and improving phase sensitivity, subtle variations and thermal stability can be observed. The experimental feasibility, advantages, and limitations of using electron holography for analyzing MRAM devices are discussed.
Article
Physics, Applied
Chexin Li, Xiaoguang Xu, Tanzhao Zhang, Zhiqiang Zhu, Qianbiao Liu, Linxuan Song, Yong Wu, Kangkang Meng, Jikun Chen, Wenhong Wang, Yong Jiang
Summary: The effect of 2D transition metal dichalcogenide MoS2 on the perpendicular magnetic anisotropy (PMA) and spin-orbit torque (SOT) of Pt/Co/Pt multilayer is revealed. MoS2 can enhance the PMA of Pt/Co/Pt multilayer and increase the SOT efficiency. Monolayer MoS2 is proved to be an ideal candidate for high-performance SOT devices.
APPLIED PHYSICS LETTERS
(2023)
Review
Physics, Applied
Ehsan Elahi, Ghulam Dastgeer, Pradeep Raj Sharma, Sobia Nisar, Muhammad Suleman, Muhammad Waqas Iqbal, Muhammad Imran, Muhammad Aslam, Ali Imran
Summary: This article reviews the progress of vertical magnetic tunnel junctions (MTJs) based on 2D materials in spin transport, analyzes the relationship between spin transportation characteristics and factors such as magnetic field and temperature, discusses the application of 2D ferromagnets in van der Waals junctions, and explores the challenges and prospects of improving spintronic devices.
JOURNAL OF PHYSICS D-APPLIED PHYSICS
(2022)
Article
Materials Science, Multidisciplinary
Z. Kurant, S. K. Jena, R. Gieniusz, U. Guzowska, M. Kisielewski, P. Mazalski, I Sveklo, A. Pietruczik, A. Lynnyk, A. Wawro, A. Maziewski
Summary: We studied the magnetic properties of epitaxial Pt/W(d(w))/Co(d(Co))/Pt layered films as a function of W(d(w)) and Co(d(Co)) layer thicknesses. The influence of the bottom W layer on magnetic anisotropy, spin reorientation transition, and magnetic polarization of the interface atoms was observed. Different magnetic states were observed with decreasing Co layer thickness. The transition from hard to soft magnetic material with out-of-plane magnetization was found with changing W layer thickness. The domain structures at the out-of-plane state were sensitive to both Co and W layer thicknesses as well as the external magnetic field. Dzyaloshinskii-Moriya interaction was inferred from the Brillouin light scattering measurements.
JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS
(2022)
Article
Physics, Applied
Pinkesh Kumar Mishra, Nareshkumar Halavath, Swapnil Bhuktare
Summary: This study investigates the improvement of the writing mechanism in magnetic memory by utilizing the stress and exchange bias provided by an antiferromagnetic material. The combination of the voltage controlled magnetic anisotropy effect and stress effect enables field-free switching, leading to a significant decrease in the write error rate.
JOURNAL OF APPLIED PHYSICS
(2023)
Article
Multidisciplinary Sciences
Maria Almeida, Apoorva Sharma, Patrick Matthes, Nicole Koehler, Sandra Busse, Matthias Mueller, Olav Hellwig, Alexander Horn, Dietrich R. T. Zahn, Georgeta Salvan, Stefan E. Schulz
Summary: This study investigates the method of locally triggered crystallization of 10 nm thick Co-Fe-B films by laser irradiation, which can achieve similar crystallization effects compared to furnace annealing, and laser annealing has the potential to locally enhance the TMR ratio, especially for MgO capping layers with lower laser intensity requirements.
SCIENTIFIC REPORTS
(2021)
Article
Chemistry, Multidisciplinary
Delin Zhang, Mukund Bapna, Wei Jiang, Duarte Sousa, Yu-Ching Liao, Zhengyang Zhao, Yang Lv, Protyush Sahu, Deyuan Lyu, Azad Naeemi, Tony Low, Sara A. Majetich, Jian-Ping Wang
Summary: In this study, the authors demonstrate a bipolar electric field effect switching using voltage-controlled exchange coupling, which shows potential applications in energy-efficient memory and logic devices. The results indicate that this type of switch has a lower switching current density, which could eliminate major obstacles in the development of spin memory devices.
Article
Chemistry, Multidisciplinary
Victor Zatko, Simon M. -M. Dubois, Florian Godel, Marta Galbiati, Julian Peiro, Anke Sander, Cecile Carretero, Aymeric Vecchiola, Sophie Collin, Karim Bouzehouane, Bernard Servet, Frederic Petroff, Jean-Christophe Charlier, Marie-Blandine Martin, Bruno Dlubak, Pierre Seneor
Summary: This study reports on the significant spin-filtering effects in epitaxial graphene-based spin valves, particularly enhanced in the case of multilayer graphene. The combination of chemical vapor deposited multilayer graphene with high-quality epitaxial Ni(111) ferromagnetic spin source led to the obtained results. Complete nanometric spin valve junctions were fabricated using a local probe indentation process, and spin properties were extracted from the graphene-protected ferromagnetic electrode using a reference Al2O3/Co spin analyzer. The study discusses the emerging physical picture of graphene-ferromagnet systems and provides insight into the efficient spin filtering effects and the interfacial matching of the graphene layers with the spin-polarized Ni surface, showcasing the potential of low Resistance-Area (RA) graphene interfaces in spin-based devices.
Article
Physics, Applied
Masaaki Tanaka, Motoharu Furuta, Tomoyuki Ichikawa, Masaya Morishita, Yu-Min Hung, Syuta Honda, Teruo Ono, Ko Mibu
Summary: This study demonstrated the generation of perpendicularly spin-polarized electronic currents using a tunnel spin-filtering effect through insulative Fe-rich cobalt ferrite CoxFe3-xO4+delta (I-CFO) barriers with perpendicular magnetic anisotropy (PMA). The combination of well-controlled compositions and lattice strains in spinel-type C-CFO and I-CFO films is applicable as a spin-injection source for spintronics devices when perpendicularly spin-polarized electronic currents are required.
APPLIED PHYSICS LETTERS
(2023)
Article
Chemistry, Physical
Duo Zhao, Mingming Wei, Feng Yang, Wei-xiao Ji, Jianguo Lu, Yu-Jia Zeng, Xiaopeng Yang
Summary: Based on first-principles calculations, this study shows that vdW materials VBr3 and VCl3 exhibit robust intrinsic half-metal properties and provide reliable guarantees for the performance of MTJ devices, and the coercivity of the magnetic electrodes can be tuned by adjusting the number of layers.
SURFACES AND INTERFACES
(2022)
Article
Chemistry, Analytical
Marcio A. Correa, Andrey V. Svalov, Armando Ferreira, Matheus Gamino, Edimilson F. da Silva, Felipe Bohn, Filipe Vaz, Danniel F. de Oliveira, Galina V. Kurlyandskaya
Summary: Thermoelectric phenomena are promising for sensor applications in renewable energy. This study reveals the mechanism of how Pt enhances the thermoelectric response in flexible electronic materials and designs a flexible thermopile without the lithography process.
Article
Materials Science, Multidisciplinary
Sk. Ziaur Rahaman, Yao-Jen Chang, Yu-Chen Hsin, Shan-Yi Yang, Hsin-Han Lee, I. -Jung Wang, Guan-Long Chen, Yi-Hui Su, Jeng-Hua Wei, Shyh-Shyuan Sheu, Wei -Chung Lo, Duan-Li Deng, Shih-Chieh Chang
Summary: The generation of torques in heavy metal and ferromagnet heterostructures in SOT-MRAM makes them attractive for magnetic memory technology. However, the current manufacturing tools present major challenges for etching in SOT-MRAM. In this study, we experimentally investigated two different etching recipes, CF-Etch and NH-Etch, and their effects on the performance of Ta/CoFeB/MgO/Ta magnetic film stacks for SOT-MRAM development.
JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS
(2023)
Article
Nanoscience & Nanotechnology
Birui Wu, Menghao Jin, Yongming Luo, Xiuyuan Xu, Haodong Fan, Haixia Huang, Zhongshu Feng, Yanshan Zhuang, Changqiu Yu, Tiejun Zhou
Summary: It has been found that in the presence of the in situ field, a small in-plane bias field and field-free switching of perpendicular magnetization can be observed. Furthermore, the damping-like fields are much enhanced.
ACS APPLIED MATERIALS & INTERFACES
(2022)
Article
Engineering, Electrical & Electronic
M. Niwa, K. Kimura, T. Naijo, A. Oshurahunov, S. Nagamachi, H. Inoue, H. Honjo, S. Ikeda, T. Endoh
Summary: The study successfully observed the microstructure of nano-scale CoFeB-MgO-based magnetic tunnel junctions, identified the root cause of resistance changes, determined the composition of the altered region inside the MTJ, and confirmed the effectiveness of STEM tomography in failure analysis.
IEEE TRANSACTIONS ON MAGNETICS
(2021)
Article
Engineering, Electrical & Electronic
Hiroki Koike, Takaho Tanigawa, Toshinari Watanabe, Takashi Nasuno, Yasuo Noguchi, Mitsuo Yasuhira, Toru Yoshiduka, Yitao Ma, Hiroaki Honjo, Koichi Nishioka, Sadahiko Miura, Hirofumi Inoue, Shoji Ikeda, Tetsuo Endoh
Summary: The development of STT-MRAM technology is ongoing and faces challenges such as further device scaling. A new circuit proposed in the study using an averaged reference voltage generator successfully reduced the fail bit rate. Through simulations and design of a 128 Mb STT-MRAM chip, the operation of the proposed device-variation tolerant array architecture was demonstrated successfully for the first time.
IEEE TRANSACTIONS ON MAGNETICS
(2021)
Article
Nanoscience & Nanotechnology
H. Honjo, H. Naganuma, T. V. A. Nguyen, H. Inoue, M. Yasuhira, S. Ikeda, T. Endoh
Summary: The study showed that applying SMT to the bottom Pt layer increased the PMA of the overlying Co/Pt multilayer, leading to better thermal tolerance and magnetic properties of the MTJs with a Co/Pt synthetic ferrimagnetic coupling reference layer.
Article
Nanoscience & Nanotechnology
K. Nishioka, H. Honjo, H. Naganuma, T. V. A. Nguyen, M. Yasuhira, S. Ikeda, T. Endoh
Summary: The research shows that the thickness of the W insertion layer affects the magnetic coupling energy and effective perpendicular magnetic anisotropy in conventional double-MTJs. There is a trade-off relationship between J(cpl) and K(eff)t(*), but adding a ferromagnetic bridge layer can improve J(cpl) while maintaining the maximum value of K(eff)t(*).
Article
Engineering, Electrical & Electronic
Masanori Natsui, Akira Tamakoshi, Hiroaki Honjo, Toshinari Watanabe, Takashi Nasuno, Chaoliang Zhang, Takaho Tanigawa, Hirofumi Inoue, Masaaki Niwa, Toru Yoshiduka, Yasuo Noguchi, Mitsuo Yasuhira, Yitao Ma, Hui Shen, Shunsuke Fukami, Hideo Sato, Shoji Ikeda, Hideo Ohno, Tetsuo Endoh, Takahiro Hanyu
Summary: The article introduces a nonvolatile memory technology called SOT-MRAM based on spin-orbit torque, which has read-disturbance-free characteristic and implements a new read-energy reduction technique. The measurement results demonstrate that under a magnetic-field-free condition, SOT-MRAM achieves high-speed write and read operations.
IEEE JOURNAL OF SOLID-STATE CIRCUITS
(2021)
Article
Multidisciplinary Sciences
Raghav Sharma, Rahul Mishra, Tung Ngo, Yong-Xin Guo, Shunsuke Fukami, Hideo Sato, Hideo Ohno, Hyunsoo Yang
Summary: This study demonstrates the electrical synchronization of four non-vortex uniformly-magnetized STOs using a single common current source in both parallel and series configurations, resolving the frequency-area quandary for designing on-chip communication systems based on STOs. Additionally, by integrating the electrically connected eight STOs, the researchers successfully demonstrate a wireless and battery-free energy harvesting system.
NATURE COMMUNICATIONS
(2021)
Article
Physics, Applied
Kerem Y. Camsari, Mustafa Mert Torunbalci, William A. Borders, Hideo Ohno, Shunsuke Fukami
Summary: The study introduces a novel MTJ design with two circular disk-shaped free layers, enabling random resistance fluctuations over a wide range of bias values. This design can be manufactured using present-day MRAM technology and serves as a hardware accelerator in energy-efficient computing schemes.
PHYSICAL REVIEW APPLIED
(2021)
Article
Materials Science, Multidisciplinary
A. K. Dhiman, T. Dohi, W. Dobrogowski, Z. Kurant, I Sveklo, S. Fukami, H. Ohno, A. Maziewski
Summary: Magnetization processes and magnetic domain structures in Ta/CoFeB/MgO stacks were studied, showing a magnetization reorientation from out-of-plane to in-plane as the CoFeB thickness increased. The thickness dependence of magnetic anisotropy and the identification of an easy-cone magnetization region were important findings in the study.
JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS
(2021)
Article
Multidisciplinary Sciences
Rajeswari Roy Chowdhury, Samik DuttaGupta, Chandan Patra, Oleg A. Tretiakov, Sudarshan Sharma, Shunsuke Fukami, Hideo Ohno, Ravi Prakash Singh
Summary: This study investigates the effect of Co-doping on the magnetic and magnetotransport properties of Fe3GeTe2, revealing a considerable modification on the Hall effect behavior, possibly due to the underlying complex spin textures. These results provide important clues for the development of spintronic devices based on 2D vdW magnetic materials.
SCIENTIFIC REPORTS
(2021)
Article
Engineering, Electrical & Electronic
H. Honjo, H. Naganuma, K. Nishioka, T. V. A. Nguyen, M. Yasuhira, S. Ikeda, T. Endoh
Summary: We investigated the effects of sputtering conditions for the deposition of an Iridium (Ir) layer on the magnetic properties and tunnel magnetoresistance ratio (TMR ratio) of magnetic tunnel junctions (MTJs) stacks. the exchange coupling field (H-ex) of Ir-SyF was improved by reducing the energy of Ir recoil ions and two times larger than that with Ru-SyF. Energy dispersive X-ray (EDX) spectrometry line analysis revealed greater interlayer diffusion in Ir when Ir was sputtered by using a conditions with large recoiled energy. Despite the larger H-ex, the TMR ratio of the MTJ with Ir-SyF is smaller than that with Ru-SyF. The m-H curve of MTJ with Ru-SyF showed a large plateau region around zero magnetic field, whereas that with Ir-SyF did not. These results indicated the degradation of perpendicular magnetic anisotropy (PMA) in the top part of the Co/Pt multilayer with CoFeB reference layer and a large biquadratic coupling effect in the thin Ir layer. This causes the deterioration of the TMR ratio of the MTJ with Ir-SyF. TEM image of the Co/Pt layer in the MTJ with Ir shows some lattice defects. The EDX line analysis revealed that a large amount of Pt in the top Co/Pt layer diffused toward CoFeB reference layer in the Ir-SyF, resulting in the degradation of PMA. The structural analysis by X-ray diffraction showed the lattice spacing of CoPt (111) in Ir-SyF to be larger than that in Ru-SyF, indicating the occurrence of strain relaxation at the Co/Pt interface. These crystallographic changes in Ir-SyF might be related to a larger Pt diffusion. Suppression of Pt diffusion as well as low damage Ir deposition in the reference layer is crucial to utilize Ir-SyF.
IEEE TRANSACTIONS ON MAGNETICS
(2022)
Article
Engineering, Electrical & Electronic
H. Honjo, K. Nishioka, S. Miura, H. Naganuma, T. Watanabe, Y. Noguchi, T. V. A. Nguyen, M. Yasuhira, S. Ikeda, T. Endoh
Summary: Perpendicular magnetic tunnel junctions (MTJs) with four synthetic anti-ferromagnetically coupled Co/Pt layers were developed and showed higher tunnel magnetoresistance ratio and stability at high temperatures compared to conventional double-SyF. In contrast, conventional double-SyF exhibited magnetization direction flipping and back-hopping under external magnetic fields.
IEEE TRANSACTIONS ON MAGNETICS
(2022)
Article
Engineering, Electrical & Electronic
K. Nishioka, S. Miura, H. Honjo, H. Naganuma, T. V. A. Nguyen, T. Watanabe, S. Ikeda, T. Endoh
Summary: The effect of magnetic coupling on the thermal stability factor Delta in magnetic tunnel junctions (MTJs) was investigated. It was found that increasing the energy constant J(cpl) of magnetic coupling can enhance Delta, but saturates when J(cpl) exceeds a critical value J(cpl_c). The magnetic static coupling constant J(stat) was much smaller than J(cpl_c), and an interlayer exchange coupling constant J(ex_c) is required to cover the difference between J(cpl_c) and J(stat). Experimental results were in good agreement with calculations, showing that Delta can be enhanced by adjusting the stiffness constant As.
IEEE TRANSACTIONS ON MAGNETICS
(2022)
Article
Nanoscience & Nanotechnology
Hiroshi Naganuma, Hiroaki Honjo, Chioko Kaneta, Koichi Nishioka, Shoji Ikeda, Tetsuo Endoh
Summary: The influence of sidewall damage on the thermal stability factor of quad-interface magnetic tunnel junctions is investigated through micromagnetic simulation. Sidewall damage causes a split in the energy barrier, resulting in decreased thermal stability.
Article
Materials Science, Multidisciplinary
Takaaki Dohi, Shunsuke Fukami, Hideo Ohno
Summary: The study reveals the critical influence of domain wall anisotropy on the current-induced hysteresis loop shift scheme for determining the magnitude of the Dzyaloshinskii-Moriya effective field. It shows quantitative agreement between the hysteresis loop shift and other techniques for small DMI systems, while also highlighting the nonlinearity in spin-orbit torque efficiency in large DMI systems due to the domain wall anisotropy.
Article
Materials Science, Multidisciplinary
Shun Kanai, Keisuke Hayakawa, Hideo Ohno, Shunsuke Fukami
Summary: By theoretically investigating the switching dynamics of stochastic nanomagnets, we uncover distinct mechanisms and reveal the impact of various factors on the relaxation time. Our work introduces the concept of entropy into understanding the dynamics, and provides insights into the material/device design for achieving shorter relaxation times.
