Advances in Antiferromagnetic Spintronics

A special issue of Magnetochemistry (ISSN 2312-7481). This special issue belongs to the section "Spin Crossover and Spintronics".

Deadline for manuscript submissions: closed (20 November 2021) | Viewed by 20685

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Special Issue Editor

Center for Science and Innovation in Spintronics, Tohoku University, Sendai 980-8577, Japan
Interests: spintronics; half-metallic ferromagnets; quantum nanoelectronics; nano-spintronic devices
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Special Issue Information

Dear Colleagues,

Antiferromagnetic spintronics is one of the emerging topics in spintronics due to a wide range of advantages, including terahertz operation, no stray field, and highly efficient spin generation. The discussion of this topic covers aspects ranging from the development of new antiferromagnetic materials to the applications of these materials in devices. Traditionally, antiferromagnets were treated as less common magnetic materials for fundamental studies and applications. However, recent miniaturisation and high-frequency operation have revealed them to be advantageous over the conventional ferromagnets. This Special Issue reviews the current status and future perspectives of antiferromagnetic spintronics.

Prof. Dr. Atsufumi Hirohata
Guest Editor

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Keywords

  • Antiferromagnets 
  • Compensated ferrimagnets 
  • Spintronics 
  • Spin current 
  • Spin Hall effect 
  • Spin caloritronics

Published Papers (8 papers)

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Editorial

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3 pages, 605 KiB  
Editorial
Advances in Antiferromagnetic Spintronics
Magnetochemistry 2022, 8(4), 37; https://doi.org/10.3390/magnetochemistry8040037 - 28 Mar 2022
Viewed by 2420
Abstract
Magnetoresistance (MR) controls signal-to-noise ratios and the corresponding size of conventional spintronic devices [...] Full article
(This article belongs to the Special Issue Advances in Antiferromagnetic Spintronics)
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Research

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8 pages, 3676 KiB  
Article
Deposition of Crystalline GdIG Samples Using Metal Organic Decomposition Method
Magnetochemistry 2022, 8(3), 28; https://doi.org/10.3390/magnetochemistry8030028 - 27 Feb 2022
Cited by 4 | Viewed by 2814
Abstract
Fabrication of high quality ferrimagnetic insulators is an essential step for ultrafast magnonics, which utilizes antiferromagnetic exchange of the ferrimagnetic materials. In this work, we deposit high-quality GdIG thin films on a (111)-oriented GGG substrate using the Metal Organic Decomposition (MOD) method, a [...] Read more.
Fabrication of high quality ferrimagnetic insulators is an essential step for ultrafast magnonics, which utilizes antiferromagnetic exchange of the ferrimagnetic materials. In this work, we deposit high-quality GdIG thin films on a (111)-oriented GGG substrate using the Metal Organic Decomposition (MOD) method, a simple and high throughput method for depositing thin film materials. We postannealed samples at various temperatures and examined the effect on structural properties such as crystallinity and surface morphology. We found a transition in the growth mode that radically changes the morphology of the film as a function of annealing temperature and obtained an optimal annealing temperature for a uniform thin film with high crystallinity. Optimized GdIG has a high potential for spin wave applications with a low damping parameter in the order of 10−3, which persists down to cryogenic temperatures. Full article
(This article belongs to the Special Issue Advances in Antiferromagnetic Spintronics)
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11 pages, 484 KiB  
Article
Theory of Antiferromagnet-Based Detector of Terahertz Frequency Signals
Magnetochemistry 2022, 8(2), 26; https://doi.org/10.3390/magnetochemistry8020026 - 12 Feb 2022
Cited by 11 | Viewed by 2924
Abstract
We present a theory of a detector of terahertz-frequency signals based on an antiferromagnetic (AFM) crystal. The conversion of a THz-frequency electromagnetic signal into the DC voltage is realized using the inverse spin Hall effect in an antiferromagnet/heavy metal bilayer. An additional bias [...] Read more.
We present a theory of a detector of terahertz-frequency signals based on an antiferromagnetic (AFM) crystal. The conversion of a THz-frequency electromagnetic signal into the DC voltage is realized using the inverse spin Hall effect in an antiferromagnet/heavy metal bilayer. An additional bias DC magnetic field can be used to tune the antiferromagnetic resonance frequency. We show that if a uniaxial AFM is used, the detection of linearly polarized signals is possible only for a non-zero DC magnetic field, while circularly polarized signals can be detected in a zero DC magnetic field. In contrast, a detector based on a biaxial AFM can be used without a bias DC magnetic field for the rectification of both linearly and circularly polarized signals. The sensitivity of a proposed AFM detector can be increased by increasing the magnitude of the bias magnetic field, or by by decreasing the thickness of the AFM layer. We believe that the presented results will be useful for the practical development of tunable, sensitive and portable spintronic detectors of THz-frequency signals based of the antiferromagnetic resonance (AFMR). Full article
(This article belongs to the Special Issue Advances in Antiferromagnetic Spintronics)
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10 pages, 5499 KiB  
Article
Manipulation of Time- and Frequency-Domain Dynamics by Magnon-Magnon Coupling in Synthetic Antiferromagnets
Magnetochemistry 2022, 8(1), 7; https://doi.org/10.3390/magnetochemistry8010007 - 30 Dec 2021
Cited by 8 | Viewed by 2623
Abstract
Magnons (the quanta of spin waves) could be used to encode information in beyond Moore computing applications. In this study, the magnon coupling between acoustic mode and optic mode in synthetic antiferromagnets (SAFs) is investigated by micromagnetic simulations. For a symmetrical SAF system, [...] Read more.
Magnons (the quanta of spin waves) could be used to encode information in beyond Moore computing applications. In this study, the magnon coupling between acoustic mode and optic mode in synthetic antiferromagnets (SAFs) is investigated by micromagnetic simulations. For a symmetrical SAF system, the time-evolution magnetizations of the two ferromagnetic layers oscillate in-phase at the acoustic mode and out-of-phase at the optic mode, showing an obvious crossing point in their antiferromagnetic resonance spectra. However, the symmetry breaking in an asymmetrical SAF system by the thickness difference, can induce an anti-crossing gap between the two frequency branches of resonance modes and thereby a strong magnon-magnon coupling appears between the resonance modes. The magnon coupling induced a hybridized resonance mode and its phase difference varies with the coupling strength. The maximum coupling occurs at the bias magnetic field at which the two ferromagnetic layers oscillate with a 90° phase difference. Besides, we show how the resonance modes in SAFs change from the in-phase state to the out-of-phase state by slightly tuning the magnon-magnon coupling strength. Our work provides a clear physical picture for the understanding of magnon-magnon coupling in a SAF system and may provide an opportunity to handle the magnon interaction in synthetic antiferromagnetic spintronics. Full article
(This article belongs to the Special Issue Advances in Antiferromagnetic Spintronics)
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9 pages, 1641 KiB  
Article
Large Perpendicular Exchange Energy in TbxCo100−x/Cu(t)/[Co/Pt]2 Heterostructures
Magnetochemistry 2021, 7(11), 141; https://doi.org/10.3390/magnetochemistry7110141 - 25 Oct 2021
Cited by 3 | Viewed by 2316
Abstract
In order to realize a perpendicular exchange bias for applications, a robust and tunable exchange bias is required for spintronic applications. Here, we show the perpendicular exchange energy (PEE) in the TbxCo100−x/Cu/[Co/Pt]2 heterostructures. The structure consists of amorphous [...] Read more.
In order to realize a perpendicular exchange bias for applications, a robust and tunable exchange bias is required for spintronic applications. Here, we show the perpendicular exchange energy (PEE) in the TbxCo100−x/Cu/[Co/Pt]2 heterostructures. The structure consists of amorphous ferrimagnetic Tb–Co alloy films and ferromagnetic Co/Pt multilayers. The dependence of the PEE on the interlayer thickness of Cu and the composition of Tb–Co were analyzed. We demonstrate that the PEE can be controlled by changing the Cu interlayer thickness of 0.2 < tCu < 0.3 (nm). We found that PEE reaches a maximum value (σPw = 1 erg/cm2) at around x = 24%. We, therefore, realize the mechanism of PEE in the TbxCo100−x/Cu/[Co/Pt]2 heterostructures. We observe two competing mechanisms—one leading to an increase and the other to a decrease—which corresponds to the effect of Tb content on saturation magnetization and the coercivity of heterostructures. Sequentially, our findings show possibilities for both pinned layers in spintronics and memory device applications by producing large PEE and controlled PEE by Cu thickness, based on TbxCo100−x/Cu/[Co/Pt]2 heterostructures. Full article
(This article belongs to the Special Issue Advances in Antiferromagnetic Spintronics)
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9 pages, 1954 KiB  
Article
Growth and Characterisation of Antiferromagnetic Ni2MnAl Heusler Alloy Films
Magnetochemistry 2021, 7(9), 127; https://doi.org/10.3390/magnetochemistry7090127 - 13 Sep 2021
Cited by 3 | Viewed by 1993
Abstract
Recent rapid advancement in antiferromagnetic spintronics paves a new path for efficient computing with THz operation. To date, major studies have been performed with conventional metallic, e.g., Ir-Mn and Pt-Mn, and semiconducting, e.g., CuMnAs, antiferromagnets, which may suffer from their elemental criticality and [...] Read more.
Recent rapid advancement in antiferromagnetic spintronics paves a new path for efficient computing with THz operation. To date, major studies have been performed with conventional metallic, e.g., Ir-Mn and Pt-Mn, and semiconducting, e.g., CuMnAs, antiferromagnets, which may suffer from their elemental criticality and high resistivity. In order to resolve these obstacles, new antiferromagnetic films are under intense development for device operation above room temperature. Here, we report the structural and magnetic properties of an antiferromagnetic Ni2MnAl Heusler alloy with and without Fe and Co doping in thin film form, which has significant potential for device applications. Full article
(This article belongs to the Special Issue Advances in Antiferromagnetic Spintronics)
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10 pages, 2004 KiB  
Article
Magnetoelectric Induced Switching of Perpendicular Exchange Bias Using 30-nm-Thick Cr2O3 Thin Film
Magnetochemistry 2021, 7(3), 36; https://doi.org/10.3390/magnetochemistry7030036 - 09 Mar 2021
Cited by 6 | Viewed by 1994
Abstract
Magnetoelectric (ME) effect is a result of the interplay between magnetism and electric field and now, it is regarded as a principle that can be applied to the technique of controlling the antiferromagnetic (AFM) domain state. The ME-controlled AFM domain state can be [...] Read more.
Magnetoelectric (ME) effect is a result of the interplay between magnetism and electric field and now, it is regarded as a principle that can be applied to the technique of controlling the antiferromagnetic (AFM) domain state. The ME-controlled AFM domain state can be read out by the magnetization of the adjacent ferromagnetic layer coupled with the ME AFM layer via exchange bias. In this technique, the reduction in the ME layer thickness is an ongoing challenge. In this paper, we demonstrate the ME-induced switching of exchange bias polarity using the 30-nm thick ME Cr2O3 thin film. Two typical switching processes, the ME field cooling (MEFC) and isothermal modes, are both explored. The required ME field for the switching in the MEFC mode suggests that the ME susceptibility (α33) is not deteriorated at 30 nm thickness regime. The isothermal change of the exchange bias shows the hysteresis with respect to the electric field, and there is an asymmetry of the switching field depending on the switching direction. The quantitative analysis of this asymmetry yields α33 at 273 K of 3.7 ± 0.5 ps/m, which is comparable to the reported value for the bulk Cr2O3. Full article
(This article belongs to the Special Issue Advances in Antiferromagnetic Spintronics)
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Review

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10 pages, 2127 KiB  
Review
Recent Developments on MnN for Spintronic Applications
Magnetochemistry 2021, 7(8), 116; https://doi.org/10.3390/magnetochemistry7080116 - 11 Aug 2021
Cited by 4 | Viewed by 2096
Abstract
There is significant interest worldwide to identify new antiferromagnetic materials suitable for device applications. Key requirements for such materials are: relatively high magnetocrystalline anisotropy constant, low cost, high corrosion resistance and the ability to induce a large exchange bias, i.e., loop shift, when [...] Read more.
There is significant interest worldwide to identify new antiferromagnetic materials suitable for device applications. Key requirements for such materials are: relatively high magnetocrystalline anisotropy constant, low cost, high corrosion resistance and the ability to induce a large exchange bias, i.e., loop shift, when grown adjacent to a ferromagnetic layer. In this article, a review of recent developments on the novel antiferromagnetic material MnN is presented. This material shows potential as a replacement for the commonly used antiferromagnet of choice, i.e., IrMn. Although the results so far look promising, further work is required for the optimization of this material. Full article
(This article belongs to the Special Issue Advances in Antiferromagnetic Spintronics)
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