Abstract The rise of three-dimensional topological insulators as an attractive playground for the observation and control of various spin-orbit effects has ushered in the field of topological spintronics. To fully exploit their potential as efficient spin-orbit torque generators, it is crucial to investigate the efficiency of spin injection and transport at various topological insulator/ferromagnet interfaces, as characterized by their spin-mixing conductances and interfacial spin transparencies. Here, we use all-optical time-resolved magneto-optical Kerr effect magnetometry to demonstrate efficient room-temperature spin pumping in Sub/BiSbTe 1.5 Se 1.5 (BSTS)/Co 20 Fe 60 B 20 (CoFeB)/SiO 2 thin films. From the modulation of Gilbert damping with BSTS and CoFeB thicknesses, the spin-mixing conductances of the BSTS/CoFeB interface and the spin diffusion length in BSTS are determined. For BSTS thicknesses far exceeding the spin diffusion length, in the so-called “perfect spin sink” regime, we obtain an interfacial spin transparency as high as 0.9, promoting such systems as scintillating candidates for spin-orbitronic devices.
三维拓扑绝缘体的兴起为观察和控制各种自旋轨道效应提供了一个有吸引力的平台，从而迎来了拓扑自旋电子学领域的发展。为了充分发挥其作为高效自旋轨道转矩发生器的潜力，研究自旋注入和输运在不同拓扑绝缘体/铁磁体界面上的效率是至关重要的，其特征是自旋混合电导和界面自旋透明度。在这里，我们使用全光时间分辨磁光克尔效应磁强计来证明在Sub/BiSbTe 1.5 Se 1.5 (BSTS)/Co 20 Fe 60 b20 (CoFeB)/ sio2薄膜中有效的室温自旋泵浦。通过BSTS和CoFeB厚度对Gilbert阻尼的调制，确定了BSTS/CoFeB界面的自旋混合电导和BSTS中的自旋扩散长度。当BSTS厚度远远超过自旋扩散长度时，在所谓的“完美自旋汇”机制下，我们获得了高达0.9的界面自旋透明度，促进了该系统成为自旋轨道电子器件的闪烁候点。
{"title":"All-optical observation of giant spin transparency at the topological insulator BiSbTe1.5Se1.5/Co20Fe60B20 interface","authors":"Suchetana Mukhopadhyay, Pratap Kumar Pal, Subhadeep Manna, Chiranjib Mitra, Anjan Barman","doi":"10.1038/s41427-023-00504-w","DOIUrl":"https://doi.org/10.1038/s41427-023-00504-w","url":null,"abstract":"Abstract The rise of three-dimensional topological insulators as an attractive playground for the observation and control of various spin-orbit effects has ushered in the field of topological spintronics. To fully exploit their potential as efficient spin-orbit torque generators, it is crucial to investigate the efficiency of spin injection and transport at various topological insulator/ferromagnet interfaces, as characterized by their spin-mixing conductances and interfacial spin transparencies. Here, we use all-optical time-resolved magneto-optical Kerr effect magnetometry to demonstrate efficient room-temperature spin pumping in Sub/BiSbTe 1.5 Se 1.5 (BSTS)/Co 20 Fe 60 B 20 (CoFeB)/SiO 2 thin films. From the modulation of Gilbert damping with BSTS and CoFeB thicknesses, the spin-mixing conductances of the BSTS/CoFeB interface and the spin diffusion length in BSTS are determined. For BSTS thicknesses far exceeding the spin diffusion length, in the so-called “perfect spin sink” regime, we obtain an interfacial spin transparency as high as 0.9, promoting such systems as scintillating candidates for spin-orbitronic devices.","PeriodicalId":19382,"journal":{"name":"Npg Asia Materials","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-10-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135566618","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract Highly efficient electrocatalysts for the hydrogen evolution reaction (HER) are essential for sustainable hydrogen energy. The controllable production of hydrogen energy by water decomposition depends heavily on the catalyst, and it is extremely important to seek sustainable and highly efficient water-splitting electrocatalysts for energy applications. Herein, bimetallic RuYO 2 − x nanoparticles (Ru: 8.84 at.% and Y: 13 at.%) with high densities and low loadings were synthesized and anchored on graphene through a simple solvothermal strategy by synthesizing hydrogen yttrium ketone (H x YO 2 − x ) serving as an inserted medium. Electron microscopy demonstrated that the RuYO 2 − x /C was composed of densely arranged particles and graphene flakes. Electrochemical results showed that the RuYO 2 − x /C had a remarkably low overpotential of η 10 = 56 mV at a current density of 10 mA cm −2 in alkaline media, a Tafel slope of 63.18 mV dec −1 , and 24 h of stability. The oxygen vacancies of RuYO 2 − x /C provided a large proton storage capacity and a strong tendency to bind hydrogen atoms. DFT calculations showed that RuYO 2 − x/ C catalysts with more Ru-O-Y bonds and V O dramatically decreased the energy barrier for breaking H-OH bonds. Moreover, the robust metal-support interactions provided optimized energies for hydrogen adsorption and desorption, which explained the high activity and favorable kinetics for RuYO 2 − x /C catalytic hydrogen precipitation in alkaline electrolyte reactions. This work presents a hydrogen insertion method for the preparation of low-loading, high-density, high-performance and stable water decomposition catalysts for hydrogen production.
{"title":"Implanting HxYO2−x sites into Ru-doped graphene and oxygen vacancies for low-overpotential alkaline hydrogen evolution","authors":"Xiang Li, Wei Deng, Yun Weng, Jingjing Zhang, Haifang Mao, Tiandong Lu, Wenqian Zhang, Renqiang Yang, Fei Jiang","doi":"10.1038/s41427-023-00501-z","DOIUrl":"https://doi.org/10.1038/s41427-023-00501-z","url":null,"abstract":"Abstract Highly efficient electrocatalysts for the hydrogen evolution reaction (HER) are essential for sustainable hydrogen energy. The controllable production of hydrogen energy by water decomposition depends heavily on the catalyst, and it is extremely important to seek sustainable and highly efficient water-splitting electrocatalysts for energy applications. Herein, bimetallic RuYO 2 − x nanoparticles (Ru: 8.84 at.% and Y: 13 at.%) with high densities and low loadings were synthesized and anchored on graphene through a simple solvothermal strategy by synthesizing hydrogen yttrium ketone (H x YO 2 − x ) serving as an inserted medium. Electron microscopy demonstrated that the RuYO 2 − x /C was composed of densely arranged particles and graphene flakes. Electrochemical results showed that the RuYO 2 − x /C had a remarkably low overpotential of η 10 = 56 mV at a current density of 10 mA cm −2 in alkaline media, a Tafel slope of 63.18 mV dec −1 , and 24 h of stability. The oxygen vacancies of RuYO 2 − x /C provided a large proton storage capacity and a strong tendency to bind hydrogen atoms. DFT calculations showed that RuYO 2 − x/ C catalysts with more Ru-O-Y bonds and V O dramatically decreased the energy barrier for breaking H-OH bonds. Moreover, the robust metal-support interactions provided optimized energies for hydrogen adsorption and desorption, which explained the high activity and favorable kinetics for RuYO 2 − x /C catalytic hydrogen precipitation in alkaline electrolyte reactions. This work presents a hydrogen insertion method for the preparation of low-loading, high-density, high-performance and stable water decomposition catalysts for hydrogen production.","PeriodicalId":19382,"journal":{"name":"Npg Asia Materials","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-10-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135566807","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-10-13DOI: 10.1038/s41427-023-00502-y
Dongjoon Shin, Seunghoon Chae, Seonghyun Park, Byungseok Seo, Wonjoon Choi
Abstract High-entropy oxides (HEOs) are promising conversion-type anode materials for Li-ion batteries (LIBs) owing to their excellent cycling stabilities and rate capabilities. However, the conventional syntheses and screening processes are time-consuming and complex and require phase and interfacial segregation of individual elements. Herein, we report a rational screening strategy for LIB anodes using precisely tunable HEOs fabricated by one-step combustion syntheses with different fuel-to-oxidizer ratios (φ). A slightly lean fuel mixture (φ-0.95) enabled a suitable temperature and non-reducing atmosphere for optimal HEO syntheses. This provided high crystallinity, perfectly homogeneous elemental distributions, and adequate pore structures without selective precipitation, whereas lower or higher fuel-to-oxidizer ratios resulted in excessively porous morphologies or elemental segregation. HEO-based anodes with φ-0.95 exhibited outstanding specific capacities (1165 mAh g −1 , 80.9% retention at 0.1 A g −1 , and 791 mAh g −1 even at 3 A g −1 ), excellent rate capabilities, and stable cycling lifetimes (1252 mAh g −1 , 80.9% retention after 100 cycles at 0.2 A g −1 ). This design strategy will provide fascinating HEO electrodes that cannot be prepared with conventional fabrication methods.
摘要:高熵氧化物(HEOs)具有良好的循环稳定性和倍率性能，是锂离子电池(LIBs)极有前途的转换型负极材料。然而，传统的合成和筛选过程耗时且复杂，并且需要对单个元素进行相分离和界面分离。在此，我们报告了一种合理的筛选策略，使用一步燃烧合成的具有不同燃料-氧化剂比(φ)的精确可调谐HEOs来筛选锂离子电池阳极。稍稀薄的燃料混合物(φ-0.95)为最佳的HEO合成提供了合适的温度和非还原气氛。这提供了高结晶度、完全均匀的元素分布和足够的孔隙结构，没有选择性沉淀，而较低或较高的燃料与氧化剂比会导致过度多孔形态或元素偏析。φ-0.95的heo基阳极具有出色的比容量(1165 mAh g−1，在0.1 A g−1下保持80.9%，在3 A g−1下保持791 mAh g−1)，优异的倍率能力和稳定的循环寿命(1252 mAh g−1，在0.2 A g−1下循环100次后保持80.9%)。这种设计策略将提供传统制造方法无法制备的令人着迷的HEO电极。
{"title":"Rational engineering of high-entropy oxides for Li-ion battery anodes with finely tuned combustion syntheses","authors":"Dongjoon Shin, Seunghoon Chae, Seonghyun Park, Byungseok Seo, Wonjoon Choi","doi":"10.1038/s41427-023-00502-y","DOIUrl":"https://doi.org/10.1038/s41427-023-00502-y","url":null,"abstract":"Abstract High-entropy oxides (HEOs) are promising conversion-type anode materials for Li-ion batteries (LIBs) owing to their excellent cycling stabilities and rate capabilities. However, the conventional syntheses and screening processes are time-consuming and complex and require phase and interfacial segregation of individual elements. Herein, we report a rational screening strategy for LIB anodes using precisely tunable HEOs fabricated by one-step combustion syntheses with different fuel-to-oxidizer ratios (φ). A slightly lean fuel mixture (φ-0.95) enabled a suitable temperature and non-reducing atmosphere for optimal HEO syntheses. This provided high crystallinity, perfectly homogeneous elemental distributions, and adequate pore structures without selective precipitation, whereas lower or higher fuel-to-oxidizer ratios resulted in excessively porous morphologies or elemental segregation. HEO-based anodes with φ-0.95 exhibited outstanding specific capacities (1165 mAh g −1 , 80.9% retention at 0.1 A g −1 , and 791 mAh g −1 even at 3 A g −1 ), excellent rate capabilities, and stable cycling lifetimes (1252 mAh g −1 , 80.9% retention after 100 cycles at 0.2 A g −1 ). This design strategy will provide fascinating HEO electrodes that cannot be prepared with conventional fabrication methods.","PeriodicalId":19382,"journal":{"name":"Npg Asia Materials","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-10-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135805511","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-10-13DOI: 10.1038/s41427-023-00500-0
Yangbo Dong, Danyang Feng, Wei Li, Rui Zhang, Shuzhen Dou, Luoqi Wang, Yan Yang, Li Wang, Yang Yang, Feng Wei, Zhen-An Qiao
Abstract Gradient porous structures enable the fast capillary-directed mass transport and enhance the chemical reaction rate with optimal efficiency and minimal energy consumption. Rational design and facile synthesis of functional mesoporous materials with sheet structure and gradient mesopores still face challenges of stacked structures and unadjustable pore sizes. Herein, an interfacial co-assembly strategy for gradient mesoporous hollow silica sheets is reported. The modulated oil-water interface allows the assembly of gradient mesoporous silica layers on the water-removable ammonium sulfate crystals. The obtained mesoporous silica layers possess narrow pore size distributions (~2.2 nm and ~6.6 nm). Owing to the good mono-dispersity, sheet structure and proper pore size, the designed gradient mesoporous hollow silica sheets can serve as flexible building blocks for fabricating nanoscale molecule filtration device. Experiments reveal that the obtained nanofiltration device shows remarkable gradient rejection rates (range from 23.5 to 99.9%) for molecules with different sizes (range from 1.2 to 4.4 nm).
{"title":"Interfacial co-assembly strategy towards gradient mesoporous hollow sheet for molecule filtration","authors":"Yangbo Dong, Danyang Feng, Wei Li, Rui Zhang, Shuzhen Dou, Luoqi Wang, Yan Yang, Li Wang, Yang Yang, Feng Wei, Zhen-An Qiao","doi":"10.1038/s41427-023-00500-0","DOIUrl":"https://doi.org/10.1038/s41427-023-00500-0","url":null,"abstract":"Abstract Gradient porous structures enable the fast capillary-directed mass transport and enhance the chemical reaction rate with optimal efficiency and minimal energy consumption. Rational design and facile synthesis of functional mesoporous materials with sheet structure and gradient mesopores still face challenges of stacked structures and unadjustable pore sizes. Herein, an interfacial co-assembly strategy for gradient mesoporous hollow silica sheets is reported. The modulated oil-water interface allows the assembly of gradient mesoporous silica layers on the water-removable ammonium sulfate crystals. The obtained mesoporous silica layers possess narrow pore size distributions (~2.2 nm and ~6.6 nm). Owing to the good mono-dispersity, sheet structure and proper pore size, the designed gradient mesoporous hollow silica sheets can serve as flexible building blocks for fabricating nanoscale molecule filtration device. Experiments reveal that the obtained nanofiltration device shows remarkable gradient rejection rates (range from 23.5 to 99.9%) for molecules with different sizes (range from 1.2 to 4.4 nm).","PeriodicalId":19382,"journal":{"name":"Npg Asia Materials","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-10-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135806023","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-10-06DOI: 10.1038/s41427-023-00496-7
Guangyang Dai, Yating Jia, Bo Gao, Yi Peng, Jianfa Zhao, Yanming Ma, Changfeng Chen, Jinlong Zhu, Quan Li, Runze Yu, Changqing Jin
Abstract Recently, topological insulators (TIs) KHgX (X = As, Sb, Bi) with hourglass-shaped dispersion have attracted great interest. Different from the TIs protected by either time-reversal or mirror crystal symmorphic symmetry tested in previous experiments, these materials were proposed as the first material class whose band topology relies on nonsymmorphic symmetries. As a result, KHgX shows many exotic properties, such as hourglass-shaped electronic channels and three-dimensional doubled quantum spin Hall effects. To date, high-pressure experimental studies on these nonsymmorphic TIs are minimal. Here, we carried out high-pressure electrical measurements up to 55 GPa, together with high-pressure X-ray diffraction measurements and high-pressure structure prediction on KHgAs. We found a pressure-induced semiconductor-metal transition between ~16 and 20 GPa, followed by the appearance of superconductivity with a T c of ~3.5 K at approximately 21 GPa. The superconducting transition temperature was enhanced to a maximum of ~6.6 K at 31.8 GPa and then slowly decreased until 55 GPa. Furthermore, three high-pressure phases within 55 GPa were observed, and their crystal structures were established. Our results showed the high-pressure phase diagram of KHgAs and determined the pressure-induced superconductivity in nonsymmorphic TIs. Thus, our study can be used to facilitate further research on superconductivity and topologically nontrivial features protected by nonsymmorphic symmetries.
{"title":"Pressure-induced superconductivity in the nonsymmorphic topological insulator KHgAs","authors":"Guangyang Dai, Yating Jia, Bo Gao, Yi Peng, Jianfa Zhao, Yanming Ma, Changfeng Chen, Jinlong Zhu, Quan Li, Runze Yu, Changqing Jin","doi":"10.1038/s41427-023-00496-7","DOIUrl":"https://doi.org/10.1038/s41427-023-00496-7","url":null,"abstract":"Abstract Recently, topological insulators (TIs) KHgX (X = As, Sb, Bi) with hourglass-shaped dispersion have attracted great interest. Different from the TIs protected by either time-reversal or mirror crystal symmorphic symmetry tested in previous experiments, these materials were proposed as the first material class whose band topology relies on nonsymmorphic symmetries. As a result, KHgX shows many exotic properties, such as hourglass-shaped electronic channels and three-dimensional doubled quantum spin Hall effects. To date, high-pressure experimental studies on these nonsymmorphic TIs are minimal. Here, we carried out high-pressure electrical measurements up to 55 GPa, together with high-pressure X-ray diffraction measurements and high-pressure structure prediction on KHgAs. We found a pressure-induced semiconductor-metal transition between ~16 and 20 GPa, followed by the appearance of superconductivity with a T c of ~3.5 K at approximately 21 GPa. The superconducting transition temperature was enhanced to a maximum of ~6.6 K at 31.8 GPa and then slowly decreased until 55 GPa. Furthermore, three high-pressure phases within 55 GPa were observed, and their crystal structures were established. Our results showed the high-pressure phase diagram of KHgAs and determined the pressure-induced superconductivity in nonsymmorphic TIs. Thus, our study can be used to facilitate further research on superconductivity and topologically nontrivial features protected by nonsymmorphic symmetries.","PeriodicalId":19382,"journal":{"name":"Npg Asia Materials","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-10-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135303754","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract Nd-Fe-B-based permanent magnets are widely used for energy conversion applications. However, their usage at elevated temperatures is difficult due to the relatively low coercivity ( H c ) with respect to the anisotropy field ( H A ) of the Nd 2 Fe 14 B compound, which is typically 0.2 H A . In this work, we found that the coercivity of an (Nd 0.8 Dy 0.2 )-Fe-B sintered magnet could reach 0.4 H A , which was twice as high as the H c / H A of its Dy-free counterpart. Detailed microstructural characterizations, density functional theory and micromagnetic simulations showed that the large value of coercivity, H c = 0.4 H A , originated not only from the enhanced H A of the main phase (intrinsic factor) but also from the reduced magnetization of the thin intergranular phase (extrinsic factor). The latter was attributed to the dissolution of 4 at.% Dy in the intergranular phase that anti-ferromagnetically coupled with Fe. The reduction in the magnetization of the intergranular phase resulted in a change in the angular dependence of coercivity from the Kondorsky type for the Dy-free magnet to the Stoner–Wohlfarth-like shape for the Dy-containing magnet, indicating that the typical pinning-controlled coercivity mechanism began to show nucleation features as the magnetization of the intergranular phase was reduced by Dy substitution.
nd - fe -b基永磁体广泛应用于能量转换领域。然而，由于相对于nd2fe14b化合物的各向异性场(H A)，它们的矫顽力(H c)相对较低，通常为0.2 H A，因此在高温下使用它们是困难的。在这项工作中，我们发现(Nd 0.8 Dy 0.2)-Fe-B烧结磁体的矫顽力可以达到0.4 H A，这是其无Dy对应物的H c / H A的两倍。详细的显微组织表征、密度泛函理论和微磁模拟表明，矫顽力的大值(H c = 0.4 H A)不仅源于主相的H A增强(内在因素)，也源于薄晶间相磁化强度的降低(外在因素)。后者归因于4 at的溶解。% Dy在与Fe反铁磁耦合的晶间相中。晶间相磁化强度的降低导致矫顽力的角依赖性从无Dy磁体的Kondorsky型转变为含Dy磁体的stoner - wohlfarth型，表明随着Dy取代降低了晶间相的磁化强度，典型的钉钉控制矫顽力机制开始呈现成核特征。
{"title":"Unveiling the origin of the large coercivity in (Nd, Dy)-Fe-B sintered magnets","authors":"Xin Tang, Jiangnan Li, Hossein Sepehri-Amin, Anton Bolyachkin, Andres Martin-Cid, Shintaro Kobayashi, Yoshinori Kotani, Motohiro Suzuki, Asako Terasawa, Yoshihiro Gohda, Tadakatsu Ohkubo, Tetsuya Nakamura, Kazuhiro Hono","doi":"10.1038/s41427-023-00498-5","DOIUrl":"https://doi.org/10.1038/s41427-023-00498-5","url":null,"abstract":"Abstract Nd-Fe-B-based permanent magnets are widely used for energy conversion applications. However, their usage at elevated temperatures is difficult due to the relatively low coercivity ( H c ) with respect to the anisotropy field ( H A ) of the Nd 2 Fe 14 B compound, which is typically 0.2 H A . In this work, we found that the coercivity of an (Nd 0.8 Dy 0.2 )-Fe-B sintered magnet could reach 0.4 H A , which was twice as high as the H c / H A of its Dy-free counterpart. Detailed microstructural characterizations, density functional theory and micromagnetic simulations showed that the large value of coercivity, H c = 0.4 H A , originated not only from the enhanced H A of the main phase (intrinsic factor) but also from the reduced magnetization of the thin intergranular phase (extrinsic factor). The latter was attributed to the dissolution of 4 at.% Dy in the intergranular phase that anti-ferromagnetically coupled with Fe. The reduction in the magnetization of the intergranular phase resulted in a change in the angular dependence of coercivity from the Kondorsky type for the Dy-free magnet to the Stoner–Wohlfarth-like shape for the Dy-containing magnet, indicating that the typical pinning-controlled coercivity mechanism began to show nucleation features as the magnetization of the intergranular phase was reduced by Dy substitution.","PeriodicalId":19382,"journal":{"name":"Npg Asia Materials","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-09-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135132513","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-09-29DOI: 10.1038/s41427-023-00499-4
Sudip Majumder, J. L. Drobitch, Supriyo Bandyopadhyay, Anjan Barman
Abstract We observed strong tripartite magnon-phonon-magnon coupling in a two-dimensional periodic array of magnetostrictive nanomagnets deposited on a piezoelectric substrate, forming a 2D magnetoelastic “crystal”; the coupling occurred between two Kittel-type spin wave (magnon) modes and a (non-Kittel) magnetoelastic spin wave mode caused by a surface acoustic wave (SAW) (phonons). The strongest coupling occurred when the frequencies and wavevectors of the three modes matched, leading to perfect phase matching. We achieved this condition by carefully engineering the frequency of the SAW, the nanomagnet dimensions and the bias magnetic field that determined the frequencies of the two Kittel-type modes. The strong coupling (cooperativity factor exceeding unity) led to the formation of a new quasi-particle, called a binary magnon-polaron, accompanied by nearly complete (~100%) transfer of energy from the magnetoelastic mode to the two Kittel-type modes. This coupling phenomenon exhibited significant anisotropy since the array did not have rotational symmetry in space. The experimental observations were in good agreement with the theoretical simulations.
{"title":"Formation of binary magnon polaron in a two-dimensional artificial magneto-elastic crystal","authors":"Sudip Majumder, J. L. Drobitch, Supriyo Bandyopadhyay, Anjan Barman","doi":"10.1038/s41427-023-00499-4","DOIUrl":"https://doi.org/10.1038/s41427-023-00499-4","url":null,"abstract":"Abstract We observed strong tripartite magnon-phonon-magnon coupling in a two-dimensional periodic array of magnetostrictive nanomagnets deposited on a piezoelectric substrate, forming a 2D magnetoelastic “crystal”; the coupling occurred between two Kittel-type spin wave (magnon) modes and a (non-Kittel) magnetoelastic spin wave mode caused by a surface acoustic wave (SAW) (phonons). The strongest coupling occurred when the frequencies and wavevectors of the three modes matched, leading to perfect phase matching. We achieved this condition by carefully engineering the frequency of the SAW, the nanomagnet dimensions and the bias magnetic field that determined the frequencies of the two Kittel-type modes. The strong coupling (cooperativity factor exceeding unity) led to the formation of a new quasi-particle, called a binary magnon-polaron, accompanied by nearly complete (~100%) transfer of energy from the magnetoelastic mode to the two Kittel-type modes. This coupling phenomenon exhibited significant anisotropy since the array did not have rotational symmetry in space. The experimental observations were in good agreement with the theoretical simulations.","PeriodicalId":19382,"journal":{"name":"Npg Asia Materials","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-09-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135132931","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-09-22DOI: 10.1038/s41427-023-00497-6
Tumesh Kumar Sahu, Saroj Pratap Sahu, K. P. S. S. Hembram, Jae-Kap Lee, Vasudevanpillai Biju, Prashant Kumar
Abstract Two-dimensional gallium nitride (2D GaN) with a large direct bandgap of ~5.3 eV, a high melting temperature of ~2500 °C, and a large Young’s modulus ~20 GPa developed for miniaturized interactive electronic gadgets can function at high thermal and mechanical loading conditions. Having various electronic, optoelectronic, spintronic, energy storage devices and sensors in perspective and the robust nature of 2D GaN, it is highly imperative to explore new pathways for its synthesis. Moreover, free-standing sheets will be desirable for large-area applications. We report our discovery of the synthesis of free-standing 2D GaN atomic sheets employing sonochemical exfoliation and the modified Hummers method. Exfoliated 2D GaN atomic sheets exhibit hexagonal and striped phases with microscale lateral dimensions and excellent chemical phase purity, confirmed by Raman and X-ray photoelectron spectroscopy. 2D GaN is highly stable, as confirmed by TGA measurements. While photodiode, FET, spintronics, and SERS-based molecular sensing, IRS element in 6G wireless communication applications of 2D GaN have been demonstrated, its nanocomposite with PVDF exhibits an excellent thermoplastic and piezoelectric behavior.
{"title":"Free-standing 2D gallium nitride for electronic, excitonic, spintronic, piezoelectric, thermoplastic, and 6G wireless communication applications","authors":"Tumesh Kumar Sahu, Saroj Pratap Sahu, K. P. S. S. Hembram, Jae-Kap Lee, Vasudevanpillai Biju, Prashant Kumar","doi":"10.1038/s41427-023-00497-6","DOIUrl":"https://doi.org/10.1038/s41427-023-00497-6","url":null,"abstract":"Abstract Two-dimensional gallium nitride (2D GaN) with a large direct bandgap of ~5.3 eV, a high melting temperature of ~2500 °C, and a large Young’s modulus ~20 GPa developed for miniaturized interactive electronic gadgets can function at high thermal and mechanical loading conditions. Having various electronic, optoelectronic, spintronic, energy storage devices and sensors in perspective and the robust nature of 2D GaN, it is highly imperative to explore new pathways for its synthesis. Moreover, free-standing sheets will be desirable for large-area applications. We report our discovery of the synthesis of free-standing 2D GaN atomic sheets employing sonochemical exfoliation and the modified Hummers method. Exfoliated 2D GaN atomic sheets exhibit hexagonal and striped phases with microscale lateral dimensions and excellent chemical phase purity, confirmed by Raman and X-ray photoelectron spectroscopy. 2D GaN is highly stable, as confirmed by TGA measurements. While photodiode, FET, spintronics, and SERS-based molecular sensing, IRS element in 6G wireless communication applications of 2D GaN have been demonstrated, its nanocomposite with PVDF exhibits an excellent thermoplastic and piezoelectric behavior.","PeriodicalId":19382,"journal":{"name":"Npg Asia Materials","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-09-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136010416","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-09-15DOI: 10.1038/s41427-023-00495-8
Keonhee Kim, Jae Gwang Lim, Su Man Hu, Yeonjoo Jeong, Jaewook Kim, Suyoun Lee, Joon Young Kwak, Jongkil Park, Gyu Weon Hwang, Kyeong-Seok Lee, Seongsik Park, Wook-Seong Lee, Byeong-Kwon Ju, Jong Keuk Park, Inho Kim
Abstract Various memristive devices have been proposed for use in neuromorphic computing systems as artificial synapses. Analog synaptic devices with linear conductance updates during training are efficiently essential to train neural networks. Although many different analog memristors have been proposed, a more reliable approach to implement analog synaptic devices is needed. In this study, we propose the memristor of a Cu/SiO x /implanted a-SiGe x /p ++ c-Si structure containing an a-Si layer with properly controlled conductance through Ge implantation. The a-SiGe x layer plays a multifunctional role in device operation by limiting the current overshoot, confining the heat generated during operation and preventing the silicide formation reaction between the active metal (Cu) and the Si bottom electrode. Thus, the a-SiGe x interface layer enables the formation of multi-weak filaments and induces analog switching behaviors. The TEM observation shows that the insertion of the a-SiGe x layer between SiO x and c-Si remarkably suppresses the formation of copper silicide, and reliable set/reset operations are secured. The origin of the analog switching behaviors is discussed by analyzing current-voltage characteristics and electron microscopy images. Finally, the memristive-neural network simulations show that our developed memristive devices provide high learning accuracy and are promising in future neuromorphic computing hardware.
{"title":"Multifilamentary switching of Cu/SiOx memristive devices with a Ge-implanted a-Si underlayer for analog synaptic devices","authors":"Keonhee Kim, Jae Gwang Lim, Su Man Hu, Yeonjoo Jeong, Jaewook Kim, Suyoun Lee, Joon Young Kwak, Jongkil Park, Gyu Weon Hwang, Kyeong-Seok Lee, Seongsik Park, Wook-Seong Lee, Byeong-Kwon Ju, Jong Keuk Park, Inho Kim","doi":"10.1038/s41427-023-00495-8","DOIUrl":"https://doi.org/10.1038/s41427-023-00495-8","url":null,"abstract":"Abstract Various memristive devices have been proposed for use in neuromorphic computing systems as artificial synapses. Analog synaptic devices with linear conductance updates during training are efficiently essential to train neural networks. Although many different analog memristors have been proposed, a more reliable approach to implement analog synaptic devices is needed. In this study, we propose the memristor of a Cu/SiO x /implanted a-SiGe x /p ++ c-Si structure containing an a-Si layer with properly controlled conductance through Ge implantation. The a-SiGe x layer plays a multifunctional role in device operation by limiting the current overshoot, confining the heat generated during operation and preventing the silicide formation reaction between the active metal (Cu) and the Si bottom electrode. Thus, the a-SiGe x interface layer enables the formation of multi-weak filaments and induces analog switching behaviors. The TEM observation shows that the insertion of the a-SiGe x layer between SiO x and c-Si remarkably suppresses the formation of copper silicide, and reliable set/reset operations are secured. The origin of the analog switching behaviors is discussed by analyzing current-voltage characteristics and electron microscopy images. Finally, the memristive-neural network simulations show that our developed memristive devices provide high learning accuracy and are promising in future neuromorphic computing hardware.","PeriodicalId":19382,"journal":{"name":"Npg Asia Materials","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-09-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135354161","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：