Pub Date : 2024-12-04DOI: 10.1038/s44306-024-00062-z
Alban Joseph, Jayakrishnan M. P. Nair, Mawgan A. Smith, Rory Holland, Luke J. McLellan, Isabella Boventer, Tim Wolz, Dmytro A. Bozhko, Benedetta Flebus, Martin P. Weides, Rair Macêdo
Recently the field of cavity magnonics, a field focused on controlling the interaction between magnons and photons confined within microwave resonators, has drawn significant attention as it offers a platform for enabling advancements in quantum- and spin-based technologies. Here, we introduce excitation vector fields, whose polarisation and profile can be easily tuned in a two-port cavity setup, thus acting as an effective experimental dial to explore the coupled dynamics of cavity magnon-polaritons. Moreover, we develop theoretical models that accurately predict and reproduce the experimental results for any polarisation state and field profile within the cavity resonator. This versatile experimental platform offers a new avenue for controlling spin-photon interactions by manipulating the polarisation of excitation fields. By introducing real-time tunable parameters that control the polarisation state, our experiment delivers a mechanism to readily control the exchange of information between hybrid systems.
{"title":"The role of excitation vector fields and all-polarisation state control in cavity magnonics","authors":"Alban Joseph, Jayakrishnan M. P. Nair, Mawgan A. Smith, Rory Holland, Luke J. McLellan, Isabella Boventer, Tim Wolz, Dmytro A. Bozhko, Benedetta Flebus, Martin P. Weides, Rair Macêdo","doi":"10.1038/s44306-024-00062-z","DOIUrl":"10.1038/s44306-024-00062-z","url":null,"abstract":"Recently the field of cavity magnonics, a field focused on controlling the interaction between magnons and photons confined within microwave resonators, has drawn significant attention as it offers a platform for enabling advancements in quantum- and spin-based technologies. Here, we introduce excitation vector fields, whose polarisation and profile can be easily tuned in a two-port cavity setup, thus acting as an effective experimental dial to explore the coupled dynamics of cavity magnon-polaritons. Moreover, we develop theoretical models that accurately predict and reproduce the experimental results for any polarisation state and field profile within the cavity resonator. This versatile experimental platform offers a new avenue for controlling spin-photon interactions by manipulating the polarisation of excitation fields. By introducing real-time tunable parameters that control the polarisation state, our experiment delivers a mechanism to readily control the exchange of information between hybrid systems.","PeriodicalId":501713,"journal":{"name":"npj Spintronics","volume":" ","pages":"1-9"},"PeriodicalIF":0.0,"publicationDate":"2024-12-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.nature.com/articles/s44306-024-00062-z.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142762916","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-12-04DOI: 10.1038/s44306-024-00065-w
Ni Wang, Ju Chen, Yipeng An, Qingfeng Zhan, Shi-Jing Gong
Modulable electronic and magnetic structures significantly extend the properties and applications of two-dimensional (2D) materials. 2D antiferromagnets (AFM) can even become ferromagnets (FM) by various approaches, which ignites growing research interests in 2D AFM. Through first-principles calculations, we find that the adsorption of Li (electron doping) and F (hole doping) on the surface of MnPSe3 can induce half-metallicity with opposite spin polarizations. The adsorption site, concentration, charge transfer, and the exchange energy are investigated in detail, indicating the robustness of half-metallicity. At the interface of MnPS3/Au(111) heterostructure, we find electrons transfer from Au(111) to MnPS3, forming the Ohmic contact and inducing AFM-FM transition. All our results show that ferromagnetic MnPX3 (X = S and Se) monolayer with half-metallicity can be easily obtained, which may be of great significance in 2D spintronic materials and devices.
{"title":"Controllable half-metallicity in MnPX3 monolayer","authors":"Ni Wang, Ju Chen, Yipeng An, Qingfeng Zhan, Shi-Jing Gong","doi":"10.1038/s44306-024-00065-w","DOIUrl":"10.1038/s44306-024-00065-w","url":null,"abstract":"Modulable electronic and magnetic structures significantly extend the properties and applications of two-dimensional (2D) materials. 2D antiferromagnets (AFM) can even become ferromagnets (FM) by various approaches, which ignites growing research interests in 2D AFM. Through first-principles calculations, we find that the adsorption of Li (electron doping) and F (hole doping) on the surface of MnPSe3 can induce half-metallicity with opposite spin polarizations. The adsorption site, concentration, charge transfer, and the exchange energy are investigated in detail, indicating the robustness of half-metallicity. At the interface of MnPS3/Au(111) heterostructure, we find electrons transfer from Au(111) to MnPS3, forming the Ohmic contact and inducing AFM-FM transition. All our results show that ferromagnetic MnPX3 (X = S and Se) monolayer with half-metallicity can be easily obtained, which may be of great significance in 2D spintronic materials and devices.","PeriodicalId":501713,"journal":{"name":"npj Spintronics","volume":" ","pages":"1-7"},"PeriodicalIF":0.0,"publicationDate":"2024-12-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.nature.com/articles/s44306-024-00065-w.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142762929","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-29DOI: 10.1038/s44306-024-00063-y
Hendrik Ohldag
Recently, altermagnets emerged as a new class of magnets which have re-energized efforts to describe the fundamentals of magnetism. This Editorial introduces the concept of altermagnetism and describes recent breakthroughs in its comprehension.
{"title":"Hidden in not-so-plain sight: altermagnets","authors":"Hendrik Ohldag","doi":"10.1038/s44306-024-00063-y","DOIUrl":"10.1038/s44306-024-00063-y","url":null,"abstract":"Recently, altermagnets emerged as a new class of magnets which have re-energized efforts to describe the fundamentals of magnetism. This Editorial introduces the concept of altermagnetism and describes recent breakthroughs in its comprehension.","PeriodicalId":501713,"journal":{"name":"npj Spintronics","volume":" ","pages":"1-1"},"PeriodicalIF":0.0,"publicationDate":"2024-11-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.nature.com/articles/s44306-024-00063-y.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142737641","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-29DOI: 10.1038/s44306-024-00061-0
Roman Adam, Derang Cao, Daniel E. Bürgler, Sarah Heidtfeld, Fangzhou Wang, Christian Greb, Jing Cheng, Debamitra Chakraborty, Ivan Komissarov, Markus Büscher, Martin Mikulics, Hilde Hardtdegen, Roman Sobolewski, Claus M. Schneider
The mechanism of THz generation in ferromagnet/metal (F/M) bilayers has been typically ascribed to the inverse spin Hall effect (ISHE). Here, we fabricated Pt/Fe/Cr/Fe/Pt multilayers containing two back-to-back spintronic THz emitters separated by a thin (tCr≤ 3nm) wedge-shaped Cr spacer. In such an arrangement, magnetization alignment of the two Fe films can be controlled by the interplay between Cr-mediated interlayer exchange coupling (IEC) and an external magnetic field. This in turn results in a strong variation of the THz amplitude A, with A↑↓ reaching up to 14 times A↑↑ (arrows indicate the relative alignment of the magnetization of the two magnetic layers). This observed functionality is ascribed to the interference of THz transients generated by two closely spaced THz emitters. Moreover, the magnetic field dependence A(H) shows a strong asymmetry that points to an additional performance modulation of the THz emitter via IEC and multilayer design.
{"title":"THz generation by exchange-coupled spintronic emitters","authors":"Roman Adam, Derang Cao, Daniel E. Bürgler, Sarah Heidtfeld, Fangzhou Wang, Christian Greb, Jing Cheng, Debamitra Chakraborty, Ivan Komissarov, Markus Büscher, Martin Mikulics, Hilde Hardtdegen, Roman Sobolewski, Claus M. Schneider","doi":"10.1038/s44306-024-00061-0","DOIUrl":"10.1038/s44306-024-00061-0","url":null,"abstract":"The mechanism of THz generation in ferromagnet/metal (F/M) bilayers has been typically ascribed to the inverse spin Hall effect (ISHE). Here, we fabricated Pt/Fe/Cr/Fe/Pt multilayers containing two back-to-back spintronic THz emitters separated by a thin (tCr≤ 3nm) wedge-shaped Cr spacer. In such an arrangement, magnetization alignment of the two Fe films can be controlled by the interplay between Cr-mediated interlayer exchange coupling (IEC) and an external magnetic field. This in turn results in a strong variation of the THz amplitude A, with A↑↓ reaching up to 14 times A↑↑ (arrows indicate the relative alignment of the magnetization of the two magnetic layers). This observed functionality is ascribed to the interference of THz transients generated by two closely spaced THz emitters. Moreover, the magnetic field dependence A(H) shows a strong asymmetry that points to an additional performance modulation of the THz emitter via IEC and multilayer design.","PeriodicalId":501713,"journal":{"name":"npj Spintronics","volume":" ","pages":"1-8"},"PeriodicalIF":0.0,"publicationDate":"2024-11-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.nature.com/articles/s44306-024-00061-0.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142737665","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-21DOI: 10.1038/s44306-024-00057-w
Hongyang Ma, James H. Cullen, Serajum Monir, Rajib Rahman, Dimitrie Culcer
The spin-Hall effect underpins some of the most active topics in modern physics, including spin torques and the inverse spin-Hall effect, yet it lacks a proper theoretical description. This makes it difficult to differentiate the SHE from other mechanisms, as well as differentiate band structure and disorder contributions. Here, by exploiting recent analytical breakthroughs in the understanding of the intrinsic spin-Hall effect, we devise a density functional theory method for evaluating the conserved (proper) spin current in a generic system. Spin non-conservation makes the conventional spin current physically meaningless, while the conserved spin current has been challenging to evaluate since it involves the position operator between Bloch bands. The novel method we introduce here can handle band structures with arbitrary degeneracies and incorporates all matrix elements of the position operator, including the notoriously challenging diagonal elements, which are associated with Fermi surface, group velocity, and dipolar effects but often diverge if not treated correctly. We apply this method to the most important classes of spin-Hall materials: topological insulators, 2D quantum spin-Hall insulators, non-collinear antiferromagnets, and strongly spin-orbit coupled metals. We demonstrate that the torque dipole systematically suppresses contributions to the conventional spin current such that, the proper spin current is generally smaller in magnitude and often has a different sign. Remarkably, its energy-dependence is relatively flat and featureless, and its magnitude is comparable in all classes of materials studied. These findings will guide the experiment in characterizing charge-to-spin interconversion in spintronic and orbitronic devices. We also discuss briefly a potential generalization of the method to calculate extrinsic spin currents generated by disorder scattering.
{"title":"Spin-Hall effect in topological materials: evaluating the proper spin current in systems with arbitrary degeneracies","authors":"Hongyang Ma, James H. Cullen, Serajum Monir, Rajib Rahman, Dimitrie Culcer","doi":"10.1038/s44306-024-00057-w","DOIUrl":"10.1038/s44306-024-00057-w","url":null,"abstract":"The spin-Hall effect underpins some of the most active topics in modern physics, including spin torques and the inverse spin-Hall effect, yet it lacks a proper theoretical description. This makes it difficult to differentiate the SHE from other mechanisms, as well as differentiate band structure and disorder contributions. Here, by exploiting recent analytical breakthroughs in the understanding of the intrinsic spin-Hall effect, we devise a density functional theory method for evaluating the conserved (proper) spin current in a generic system. Spin non-conservation makes the conventional spin current physically meaningless, while the conserved spin current has been challenging to evaluate since it involves the position operator between Bloch bands. The novel method we introduce here can handle band structures with arbitrary degeneracies and incorporates all matrix elements of the position operator, including the notoriously challenging diagonal elements, which are associated with Fermi surface, group velocity, and dipolar effects but often diverge if not treated correctly. We apply this method to the most important classes of spin-Hall materials: topological insulators, 2D quantum spin-Hall insulators, non-collinear antiferromagnets, and strongly spin-orbit coupled metals. We demonstrate that the torque dipole systematically suppresses contributions to the conventional spin current such that, the proper spin current is generally smaller in magnitude and often has a different sign. Remarkably, its energy-dependence is relatively flat and featureless, and its magnitude is comparable in all classes of materials studied. These findings will guide the experiment in characterizing charge-to-spin interconversion in spintronic and orbitronic devices. We also discuss briefly a potential generalization of the method to calculate extrinsic spin currents generated by disorder scattering.","PeriodicalId":501713,"journal":{"name":"npj Spintronics","volume":" ","pages":"1-10"},"PeriodicalIF":0.0,"publicationDate":"2024-11-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.nature.com/articles/s44306-024-00057-w.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142692148","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-21DOI: 10.1038/s44306-024-00054-z
Guiping Ji, Yuejie Zhang, Yahong Chai, Tianxiang Nan
Spin-orbit torques (SOTs) provide an energy-efficient approach for the electrical manipulation of magnetization, pivotal for next-generation information storage and processing devices. SOTs can be generated via various mechanisms, such as spin Hall effect, Rashba-Edelstein effect, orbital Hall effect, magnons, and spin swapping. SOTs-based devices hold potential advantages over spin-transfer torque (STT) devices, including low power consumption, enhanced durability, and a broader selection of applicable materials for both SOT generation and excitation. Despite the discovery of numerous materials capable of generating significant SOTs, achieving efficient and deterministic field-free switching of perpendicular magnetization remains a critical challenge, which is essential for the practical deployment of SOT in high-density magnetic memories. This review highlights recent progress in controlling SOTs through innovative materials design, encompassing strategies such as strain engineering of the spin Hall angle, interfacial engineering of the spin transmissivity and topological surface states, and symmetry engineering to achieve deterministic field-free switching of perpendicular magnetization. By exploring these effective methods for manipulating SOTs, this review aims to lay the groundwork for the development of optimized spintronics devices and applications.
自旋轨道力矩（SOT）为磁化的电操纵提供了一种节能方法，对下一代信息存储和处理设备至关重要。自旋轨道力矩可通过各种机制产生，如自旋霍尔效应、拉什巴-爱德斯坦效应、轨道霍尔效应、磁子和自旋交换。与自旋转移力矩（STT）器件相比，基于 SOT 的器件具有潜在的优势，包括功耗低、耐用性强，以及 SOT 生成和激发的适用材料选择范围更广。尽管发现了许多能够产生显著自旋转移力矩的材料，但实现垂直磁化的高效和确定性无磁场切换仍然是一个严峻的挑战，这对于在高密度磁存储器中实际部署自旋转移力矩至关重要。本综述重点介绍通过创新材料设计控制 SOT 的最新进展，包括自旋霍尔角的应变工程、自旋透射率和拓扑表面态的界面工程以及对称性工程等策略，以实现垂直磁化的确定性无磁场切换。本综述旨在通过探讨这些操纵 SOT 的有效方法，为开发优化的自旋电子器件和应用奠定基础。
{"title":"Recent progress on controlling spin-orbit torques by materials design","authors":"Guiping Ji, Yuejie Zhang, Yahong Chai, Tianxiang Nan","doi":"10.1038/s44306-024-00054-z","DOIUrl":"10.1038/s44306-024-00054-z","url":null,"abstract":"Spin-orbit torques (SOTs) provide an energy-efficient approach for the electrical manipulation of magnetization, pivotal for next-generation information storage and processing devices. SOTs can be generated via various mechanisms, such as spin Hall effect, Rashba-Edelstein effect, orbital Hall effect, magnons, and spin swapping. SOTs-based devices hold potential advantages over spin-transfer torque (STT) devices, including low power consumption, enhanced durability, and a broader selection of applicable materials for both SOT generation and excitation. Despite the discovery of numerous materials capable of generating significant SOTs, achieving efficient and deterministic field-free switching of perpendicular magnetization remains a critical challenge, which is essential for the practical deployment of SOT in high-density magnetic memories. This review highlights recent progress in controlling SOTs through innovative materials design, encompassing strategies such as strain engineering of the spin Hall angle, interfacial engineering of the spin transmissivity and topological surface states, and symmetry engineering to achieve deterministic field-free switching of perpendicular magnetization. By exploring these effective methods for manipulating SOTs, this review aims to lay the groundwork for the development of optimized spintronics devices and applications.","PeriodicalId":501713,"journal":{"name":"npj Spintronics","volume":" ","pages":"1-14"},"PeriodicalIF":0.0,"publicationDate":"2024-11-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.nature.com/articles/s44306-024-00054-z.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142692150","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-06DOI: 10.1038/s44306-024-00058-9
Diana C. Leitao, Floris J. F. van Riel, Mahmoud Rasly, Pedro D. R. Araujo, Maria Salvador, Elvira Paz, Bert Koopmans
Spintronic sensors are uniquely positioned to deliver the next generation of high-performance magnetic field measurement tools with re-configurable key features. In this perspective article, we focus on giant and tunnel magnetoresistance sensors that exploit changes in the electrical resistance of thin films in response to an external magnetic field. We discuss strategies to address ongoing open challenges to improve operation limits. The goal is to meet current technological needs and thus expand the scope of existing applications. We also propose innovative approaches to design sensors with adaptable characteristics and embedded multifunctionality, aiming to create opportunities for future magnetic sensing applications. These solutions leverage the versatility of spintronic sensors, from the thin-film multilayers that form their building blocks, to device fabrication methods and potential integration with other technologies. The outlook of novel applications spans multiple areas, including electric vehicles, robotics, remote detection, or biomedicine.
{"title":"Enhanced performance and functionality in spintronic sensors","authors":"Diana C. Leitao, Floris J. F. van Riel, Mahmoud Rasly, Pedro D. R. Araujo, Maria Salvador, Elvira Paz, Bert Koopmans","doi":"10.1038/s44306-024-00058-9","DOIUrl":"10.1038/s44306-024-00058-9","url":null,"abstract":"Spintronic sensors are uniquely positioned to deliver the next generation of high-performance magnetic field measurement tools with re-configurable key features. In this perspective article, we focus on giant and tunnel magnetoresistance sensors that exploit changes in the electrical resistance of thin films in response to an external magnetic field. We discuss strategies to address ongoing open challenges to improve operation limits. The goal is to meet current technological needs and thus expand the scope of existing applications. We also propose innovative approaches to design sensors with adaptable characteristics and embedded multifunctionality, aiming to create opportunities for future magnetic sensing applications. These solutions leverage the versatility of spintronic sensors, from the thin-film multilayers that form their building blocks, to device fabrication methods and potential integration with other technologies. The outlook of novel applications spans multiple areas, including electric vehicles, robotics, remote detection, or biomedicine.","PeriodicalId":501713,"journal":{"name":"npj Spintronics","volume":" ","pages":"1-11"},"PeriodicalIF":0.0,"publicationDate":"2024-11-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.nature.com/articles/s44306-024-00058-9.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142588298","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-06DOI: 10.1038/s44306-024-00059-8
Kemal Selcuk, Saleh Bunaiyan, Nihal Sanjay Singh, Shehrin Sayed, Samiran Ganguly, Giovanni Finocchio, Supriyo Datta, Kerem Y. Camsari
An emerging paradigm in modern electronics is that of CMOS+ $${mathsf{X}}$$ requiring the integration of standard CMOS technology with novel materials and technologies denoted by $${mathsf{X}}$$ . In this context, a crucial challenge is to develop accurate circuit models for $${mathsf{X}}$$ that are compatible with standard models for CMOS-based circuits and systems. In this perspective, we present physics-based, experimentally benchmarked modular circuit models that can be used to evaluate a class of CMOS+ $${mathsf{X}}$$ systems, where $${mathsf{X}}$$ denotes magnetic and spintronic materials and phenomena. This class of materials is particularly challenging because they go beyond conventional charge-based phenomena and involve the spin degree of freedom which involves non-trivial quantum effects. Starting from density matrices—the central quantity in quantum transport—using well-defined approximations, it is possible to obtain spin-circuits that generalize ordinary circuit theory to 4-component currents and voltages (1 for charge and 3 for spin). With step-by-step examples that progressively become more complex, we illustrate how the spin-circuit approach can be used to start from the physics of magnetism and spintronics to enable accurate system-level evaluations. We believe the core approach can be extended to include other quantum degrees of freedom like valley and pseudospins starting from corresponding density matrices.
{"title":"Connecting physics to systems with modular spin-circuits","authors":"Kemal Selcuk, Saleh Bunaiyan, Nihal Sanjay Singh, Shehrin Sayed, Samiran Ganguly, Giovanni Finocchio, Supriyo Datta, Kerem Y. Camsari","doi":"10.1038/s44306-024-00059-8","DOIUrl":"10.1038/s44306-024-00059-8","url":null,"abstract":"An emerging paradigm in modern electronics is that of CMOS+ $${mathsf{X}}$$ requiring the integration of standard CMOS technology with novel materials and technologies denoted by $${mathsf{X}}$$ . In this context, a crucial challenge is to develop accurate circuit models for $${mathsf{X}}$$ that are compatible with standard models for CMOS-based circuits and systems. In this perspective, we present physics-based, experimentally benchmarked modular circuit models that can be used to evaluate a class of CMOS+ $${mathsf{X}}$$ systems, where $${mathsf{X}}$$ denotes magnetic and spintronic materials and phenomena. This class of materials is particularly challenging because they go beyond conventional charge-based phenomena and involve the spin degree of freedom which involves non-trivial quantum effects. Starting from density matrices—the central quantity in quantum transport—using well-defined approximations, it is possible to obtain spin-circuits that generalize ordinary circuit theory to 4-component currents and voltages (1 for charge and 3 for spin). With step-by-step examples that progressively become more complex, we illustrate how the spin-circuit approach can be used to start from the physics of magnetism and spintronics to enable accurate system-level evaluations. We believe the core approach can be extended to include other quantum degrees of freedom like valley and pseudospins starting from corresponding density matrices.","PeriodicalId":501713,"journal":{"name":"npj Spintronics","volume":" ","pages":"1-12"},"PeriodicalIF":0.0,"publicationDate":"2024-11-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.nature.com/articles/s44306-024-00059-8.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142588299","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-26DOI: 10.1038/s44306-024-00056-x
Po-Hao Chang, Igor I. Mazin
Magnetism in the Zintl compound Ba14MnBi11 is rather poorly understood. Experimental claims are largely inconsistent with ab initio calculations, much beyond typical errors of the latter. We revisit this old problem, assuming that the root of the problem may be in nonstoichiometry of existing samples. Our key finding is that the magnetic ground state is indeed very susceptible to charge doping (band filling). Calculations for stoichiometric Ba14MnBi11 give a rather stable ferromagnetic metallic state, in agreement with previous publications. However, by adding exactly one electron per Mn, the system becomes semiconducting as expected, and becomes weakly antiferromagnetic (AF). On the other hand, upon small amount of hole doping, the system transitions to a special type of AF state known as altermagnetism. Furthermore, hole and electron doping-induced phase transitions result from different underlying mechanisms, influencing different exchange pathways. We propose that the inconsistency between experiment and theory is not a failure of the latter, but results from a nontrivial ramification of nonstoichiometry. The possibility of doping-stabilized altermagnetism is exciting.
人们对 Zintl 化合物 Ba14MnBi11 的磁性了解甚少。实验结果在很大程度上与 ab initio 计算结果不一致，远远超出了后者的典型误差。我们重新审视了这个老问题，假设问题的根源可能在于现有样品的非化学计量。我们的主要发现是，磁基态确实非常容易受到电荷掺杂（带填充）的影响。通过计算化学计量 Ba14MnBi11，可以得到相当稳定的铁磁金属态，这与之前发表的文章一致。然而，当每锰恰好加入一个电子时，该体系就会如预期的那样成为半导体，并变成弱反铁磁性（AF）。另一方面，当掺入少量空穴时，体系会过渡到一种特殊的反铁磁性（AF）状态，即所谓的 "变磁"（altermagnetism）。此外，空穴掺杂和电子掺杂诱导的相变产生于不同的基本机制，影响着不同的交换途径。我们提出，实验与理论之间的不一致并不是理论的失败，而是由于非化学计量学的非微不足道的衍生物造成的。掺杂稳定变磁性的可能性令人兴奋。
{"title":"The mysterious magnetic ground state of Ba14MnBi11 is likely self-doped and altermagnetic","authors":"Po-Hao Chang, Igor I. Mazin","doi":"10.1038/s44306-024-00056-x","DOIUrl":"10.1038/s44306-024-00056-x","url":null,"abstract":"Magnetism in the Zintl compound Ba14MnBi11 is rather poorly understood. Experimental claims are largely inconsistent with ab initio calculations, much beyond typical errors of the latter. We revisit this old problem, assuming that the root of the problem may be in nonstoichiometry of existing samples. Our key finding is that the magnetic ground state is indeed very susceptible to charge doping (band filling). Calculations for stoichiometric Ba14MnBi11 give a rather stable ferromagnetic metallic state, in agreement with previous publications. However, by adding exactly one electron per Mn, the system becomes semiconducting as expected, and becomes weakly antiferromagnetic (AF). On the other hand, upon small amount of hole doping, the system transitions to a special type of AF state known as altermagnetism. Furthermore, hole and electron doping-induced phase transitions result from different underlying mechanisms, influencing different exchange pathways. We propose that the inconsistency between experiment and theory is not a failure of the latter, but results from a nontrivial ramification of nonstoichiometry. The possibility of doping-stabilized altermagnetism is exciting.","PeriodicalId":501713,"journal":{"name":"npj Spintronics","volume":" ","pages":"1-7"},"PeriodicalIF":0.0,"publicationDate":"2024-10-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.nature.com/articles/s44306-024-00056-x.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142519198","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-14DOI: 10.1038/s44306-024-00060-1
Qiming Shao
Increasing the bandwidth of existing optical fiber networks is vital as society’s appetite for information grows. This Editorial presents a spintronics-based solution in the context of recent research findings.
{"title":"Communicating with magnons","authors":"Qiming Shao","doi":"10.1038/s44306-024-00060-1","DOIUrl":"10.1038/s44306-024-00060-1","url":null,"abstract":"Increasing the bandwidth of existing optical fiber networks is vital as society’s appetite for information grows. This Editorial presents a spintronics-based solution in the context of recent research findings.","PeriodicalId":501713,"journal":{"name":"npj Spintronics","volume":" ","pages":"1-1"},"PeriodicalIF":0.0,"publicationDate":"2024-10-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.nature.com/articles/s44306-024-00060-1.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142431069","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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