Magnetic and Spin Devices, 3rd Edition

A special issue of Micromachines (ISSN 2072-666X). This special issue belongs to the section "D:Materials and Processing".

Deadline for manuscript submissions: 20 October 2024 | Viewed by 2512

Special Issue Editor


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Guest Editor
Institute for Microelectronics, Vienna University of Technology, 1040 Vienna, Austria
Interests: digital spintronics; spin-transfer torque devices; spin-orbit torque devices; in-memory computing
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Special Issue Information

Dear Colleagues,

As the scaling of electronic semiconductor devices results in saturation, the main research focus is the search for computing paradigms which employ new physics principles. Electron spinning, the intrinsic angular momentum of an electron, offers additional functionality to electron charge-based microelectronic devices. Electron spinning is characterized by two well-defined projections on a given axis and is, therefore, perfectly suited for digital data processing. Several fundamental problems, including spin injection, spin propagation, and relaxation, as well as spin manipulation using the gate voltage, have successfully been resolved to produce spin-based reprogrammable semiconductor devices. Ferromagnetic electrodes are employed to produce and inject spin-polarized currents. Devices employing magnetic contacts are non-volatile as they can preserve the information stored in the magnetization orientation without consuming external power. Spin-polarized currents can be used to change the magnetization orientation and, therefore, write digital information. As this information is recorded and read purely electrically by charge currents without magnetic fields, new non-volatile devices and memories possess excellent scalability. In addition, they also have a simple structure and offer superior endurance and data retention rates. Placing non-volatile memory elements close to CMOS helps to mitigate the Von Neumann performance bottleneck due to the data transfer between the central processing unit and the memory. It also offers a prospect of data processing in the nonvolatile segment, where the same devices can be used to store and to process information. This introduces perspectives for conceptually new low-power in-memory computing paradigms within the artificial intelligence of things.

This Special Issue focuses on all topics related to spintronic devices, such as spin-based switches, magnetoresistive memories, energy-harvesting devices, and sensors, which can be employed in in-memory computing concepts as well as the artificial intelligence of things paradigm.

Dr. Viktor Sverdlov
Guest Editor

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Keywords

  • digital spintronics
  • spin-transfer torque (STT)
  • spin-orbit torque (SOT)
  • magnetoresistive random access memory (MRAM)
  • in-memory computing
  • magnetic sensors
  • energy harvesting magnetic devices
  • artificial intelligence of things

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Published Papers (3 papers)

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Research

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14 pages, 960 KiB  
Article
Advanced Modeling and Simulation of Multilayer Spin–Transfer Torque Magnetoresistive Random Access Memory with Interface Exchange Coupling
by Mario Bendra, Roberto Lacerda de Orio, Siegfried Selberherr, Wolfgang Goes and Viktor Sverdlov
Micromachines 2024, 15(5), 568; https://doi.org/10.3390/mi15050568 - 26 Apr 2024
Viewed by 570
Abstract
In advancing the study of magnetization dynamics in STT-MRAM devices, we employ the spin drift–diffusion model to address the back-hopping effect. This issue manifests as unwanted switching either in the composite free layer or in the reference layer in synthetic antiferromagnets—a challenge that [...] Read more.
In advancing the study of magnetization dynamics in STT-MRAM devices, we employ the spin drift–diffusion model to address the back-hopping effect. This issue manifests as unwanted switching either in the composite free layer or in the reference layer in synthetic antiferromagnets—a challenge that becomes more pronounced with device miniaturization. Although this miniaturization aims to enhance memory density, it inadvertently compromises data integrity. Parallel to this examination, our investigation of the interface exchange coupling within multilayer structures unveils critical insights into the efficacy and dependability of spintronic devices. We particularly scrutinize how exchange coupling, mediated by non-magnetic layers, influences the magnetic interplay between adjacent ferromagnetic layers, thereby affecting their magnetic stability and domain wall movements. This investigation is crucial for understanding the switching behavior in multi-layered structures. Our integrated methodology, which uses both charge and spin currents, demonstrates a comprehensive understanding of MRAM dynamics. It emphasizes the strategic optimization of exchange coupling to improve the performance of multi-layered spintronic devices. Such enhancements are anticipated to encourage improvements in data retention and the write/read speeds of memory devices. This research, thus, marks a significant leap forward in the refinement of high-capacity, high-performance memory technologies. Full article
(This article belongs to the Special Issue Magnetic and Spin Devices, 3rd Edition)
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16 pages, 5257 KiB  
Article
In Situ Study of the Magnetic Field Gradient Produced by a Miniature Bi-Planar Coil for Chip-Scale Atomic Devices
by Yao Chen, Jiyang Wang, Ning Zhang, Jing Wang, Yintao Ma, Mingzhi Yu, Yanbin Wang, Libo Zhao and Zhuangde Jiang
Micromachines 2023, 14(11), 1985; https://doi.org/10.3390/mi14111985 - 26 Oct 2023
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Abstract
The miniaturization of quantum sensors is a popular trend for the development of quantum technology. One of the key components of these sensors is a coil which is used for spin modulation and manipulation. The bi-planar coils have the advantage of producing three-dimensional [...] Read more.
The miniaturization of quantum sensors is a popular trend for the development of quantum technology. One of the key components of these sensors is a coil which is used for spin modulation and manipulation. The bi-planar coils have the advantage of producing three-dimensional magnetic fields with only two planes of current confinement, whereas the traditional Helmholtz coils require three-dimensional current distribution. Thus, the bi-planar coils are compatible with the current micro-fabrication process and are quite suitable for the compact design of the chip-scale atomic devices that require stable or modulated magnetic fields. This paper presents a design of a miniature bi-planar coil. Both the magnetic fields produced by the coils and their inhomogeneities were designed theoretically. The magnetic field gradient is a crucial parameter for the coils, especially for generating magnetic fields in very small areas. We used a NMR (Nuclear Magnetic Resonance) method based on the relaxation of 131Xe nuclear spins to measure the magnetic field gradient in situ. This is the first time that the field inhomogeneities of the field of such small bi-planar coils have been measured. Our results indicate that the designed gradient caused error is 0.08 for the By and the Bx coils, and the measured gradient caused error using the nuclear spin relaxation method is 0.09±0.02, suggesting that our method is suitable for measuring gradients. Due to the poor sensitivity of our magnetometer under a large Bz bias field, we could not measure the Bz magnetic field gradient. Our method also helps to improve the gradients of the miniature bi-planar coil design, which is critical for chip-scale atomic devices. Full article
(This article belongs to the Special Issue Magnetic and Spin Devices, 3rd Edition)
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Review

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20 pages, 2278 KiB  
Review
Progress in Spin Logic Devices Based on Domain-Wall Motion
by Bob Bert Vermeulen, Bart Sorée, Sebastien Couet, Kristiaan Temst and Van Dai Nguyen
Micromachines 2024, 15(6), 696; https://doi.org/10.3390/mi15060696 - 24 May 2024
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Abstract
Spintronics, utilizing both the charge and spin of electrons, benefits from the nonvolatility, low switching energy, and collective behavior of magnetization. These properties allow the development of magnetoresistive random access memories, with magnetic tunnel junctions (MTJs) playing a central role. Various spin logic [...] Read more.
Spintronics, utilizing both the charge and spin of electrons, benefits from the nonvolatility, low switching energy, and collective behavior of magnetization. These properties allow the development of magnetoresistive random access memories, with magnetic tunnel junctions (MTJs) playing a central role. Various spin logic concepts are also extensively explored. Among these, spin logic devices based on the motion of magnetic domain walls (DWs) enable the implementation of compact and energy-efficient logic circuits. In these devices, DW motion within a magnetic track enables spin information processing, while MTJs at the input and output serve as electrical writing and reading elements. DW logic holds promise for simplifying logic circuit complexity by performing multiple functions within a single device. Nevertheless, the demonstration of DW logic circuits with electrical writing and reading at the nanoscale is still needed to unveil their practical application potential. In this review, we discuss material advancements for high-speed DW motion, progress in DW logic devices, groundbreaking demonstrations of current-driven DW logic, and its potential for practical applications. Additionally, we discuss alternative approaches for current-free information propagation, along with challenges and prospects for the development of DW logic. Full article
(This article belongs to the Special Issue Magnetic and Spin Devices, 3rd Edition)
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