Magnetochemistry

Editorial

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3 pages, 605 KiB

Open AccessEditorial

Advances in Antiferromagnetic Spintronics

by Atsufumi Hirohata

Magnetochemistry 2022, 8(4), 37; https://doi.org/10.3390/magnetochemistry8040037 - 28 Mar 2022

Viewed by 2594

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

Open AccessFeature PaperArticle

Deposition of Crystalline GdIG Samples Using Metal Organic Decomposition Method

by Hyeongyu Kim, Phuoc-Cao Van, Hyeonjung Jung, Jiseok Yang, Younghun Jo, Jung-Woo Yoo, Albert M. Park, Jong-Ryul Jeong and Kab-Jin Kim

Magnetochemistry 2022, 8(3), 28; https://doi.org/10.3390/magnetochemistry8030028 - 27 Feb 2022

Cited by 5 | Viewed by 3013

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

Open AccessFeature PaperArticle

Theory of Antiferromagnet-Based Detector of Terahertz Frequency Signals

by Ansar Safin, Sergey Nikitov, Andrei Kirilyuk, Vasyl Tyberkevych and Andrei Slavin

Magnetochemistry 2022, 8(2), 26; https://doi.org/10.3390/magnetochemistry8020026 - 12 Feb 2022

Cited by 11 | Viewed by 3176

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

Open AccessArticle

Manipulation of Time- and Frequency-Domain Dynamics by Magnon-Magnon Coupling in Synthetic Antiferromagnets

by Xing Chen, Cuixiu Zheng, Sai Zhou, Yaowen Liu and Zongzhi Zhang

Magnetochemistry 2022, 8(1), 7; https://doi.org/10.3390/magnetochemistry8010007 - 30 Dec 2021

Cited by 8 | Viewed by 2841

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

Open AccessArticle

Large Perpendicular Exchange Energy in Tb_xCo_100−x/Cu(t)/[Co/Pt]₂ Heterostructures

by Sina Ranjbar, Satoshi Sumi, Kenji Tanabe and Hiroyuki Awano

Magnetochemistry 2021, 7(11), 141; https://doi.org/10.3390/magnetochemistry7110141 - 25 Oct 2021

Cited by 3 | Viewed by 2500

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 Tb_xCo_100−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 Tb_xCo_100−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 < t_Cu < 0.3 (nm). We found that PEE reaches a maximum value (σ_Pw = 1 erg/cm²) at around x = 24%. We, therefore, realize the mechanism of PEE in the Tb_xCo_100−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 Tb_xCo_100−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

Open AccessArticle

Growth and Characterisation of Antiferromagnetic Ni₂MnAl Heusler Alloy Films

by Teodor Huminiuc, Oliver Whear, Andrew J. Vick, David C. Lloyd, Gonzalo Vallejo-Fernandez, Kevin O’Grady and Atsufumi Hirohata

Magnetochemistry 2021, 7(9), 127; https://doi.org/10.3390/magnetochemistry7090127 - 13 Sep 2021

Cited by 4 | Viewed by 2197

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

Open AccessFeature PaperArticle

Magnetoelectric Induced Switching of Perpendicular Exchange Bias Using 30-nm-Thick Cr₂O₃ Thin Film

by Yu Shiratsuchi, Yiran Tao, Kentaro Toyoki and Ryoichi Nakatani

Magnetochemistry 2021, 7(3), 36; https://doi.org/10.3390/magnetochemistry7030036 - 9 Mar 2021

Cited by 6 | Viewed by 2138

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 Cr₂O_3. 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

Open AccessReview

Recent Developments on MnN for Spintronic Applications

by Gonzalo Vallejo-Fernandez and Markus Meinert

Magnetochemistry 2021, 7(8), 116; https://doi.org/10.3390/magnetochemistry7080116 - 11 Aug 2021

Cited by 4 | Viewed by 2239

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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