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":"46 1","pages":"0"},"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":"23 1","pages":"0"},"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":"15 1","pages":"0"},"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":"50 1","pages":"0"},"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}
Pub Date : 2023-09-08DOI: 10.1038/s41427-023-00493-w
Masato Wakeda, T. Ichitsubo
{"title":"Atomistic study of liquid fragility and spatial heterogeneity of glassy solids in model binary alloys","authors":"Masato Wakeda, T. Ichitsubo","doi":"10.1038/s41427-023-00493-w","DOIUrl":"https://doi.org/10.1038/s41427-023-00493-w","url":null,"abstract":"","PeriodicalId":19382,"journal":{"name":"Npg Asia Materials","volume":" ","pages":"1-13"},"PeriodicalIF":9.7,"publicationDate":"2023-09-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43973492","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 : 2023-09-08DOI: 10.1038/s41427-023-00494-9
Mingqi Dong, Weiwei Zhou, Suxia Guo, N. Nomura
{"title":"Ultrafine-bubble-water-promoted nanoceramic decoration of metal powders for additive manufacturing","authors":"Mingqi Dong, Weiwei Zhou, Suxia Guo, N. Nomura","doi":"10.1038/s41427-023-00494-9","DOIUrl":"https://doi.org/10.1038/s41427-023-00494-9","url":null,"abstract":"","PeriodicalId":19382,"journal":{"name":"Npg Asia Materials","volume":" ","pages":"1-8"},"PeriodicalIF":9.7,"publicationDate":"2023-09-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46540504","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 : 2023-08-25DOI: 10.1038/s41427-023-00492-x
Wenqiang Zhang, Jingzhuo Zhou, Yanwen Jia, Juzheng Chen, Yiru Pu, Rong Fan, F. Meng, Qi Ge, Yang Lu
{"title":"Magnetoactive microlattice metamaterials with highly tunable stiffness and fast response rate","authors":"Wenqiang Zhang, Jingzhuo Zhou, Yanwen Jia, Juzheng Chen, Yiru Pu, Rong Fan, F. Meng, Qi Ge, Yang Lu","doi":"10.1038/s41427-023-00492-x","DOIUrl":"https://doi.org/10.1038/s41427-023-00492-x","url":null,"abstract":"","PeriodicalId":19382,"journal":{"name":"Npg Asia Materials","volume":" ","pages":"1-8"},"PeriodicalIF":9.7,"publicationDate":"2023-08-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46566773","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 : 2023-08-04DOI: 10.1038/s41427-023-00489-6
Zhen Song, You-Shan Zhang, Jinghua Shen, B. Lin, Jie Wu, P. Xiang, C. Duan, R. He
{"title":"Realizing metallicity in Sr_2IrO_4 thin films by high-pressure oxygen annealing","authors":"Zhen Song, You-Shan Zhang, Jinghua Shen, B. Lin, Jie Wu, P. Xiang, C. Duan, R. He","doi":"10.1038/s41427-023-00489-6","DOIUrl":"https://doi.org/10.1038/s41427-023-00489-6","url":null,"abstract":"","PeriodicalId":19382,"journal":{"name":"Npg Asia Materials","volume":" ","pages":"1-7"},"PeriodicalIF":9.7,"publicationDate":"2023-08-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41569274","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}
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