npj SpintronicsPub Date : 2024-06-03DOI: 10.1038/s44306-024-00025-4
C. S. Davies, A. Kirilyuk
{"title":"Epsilon-near-zero regime for ultrafast opto-spintronics","authors":"C. S. Davies, A. Kirilyuk","doi":"10.1038/s44306-024-00025-4","DOIUrl":"10.1038/s44306-024-00025-4","url":null,"abstract":"Over the last two decades, breakthrough works in the field of non-linear phononics have revealed that high-frequency lattice vibrations, when driven to high amplitude by mid- to far-infrared optical pulses, can bolster the light-matter interaction and thereby lend control over a variety of spontaneous orderings. This approach fundamentally relies on the resonant excitation of infrared-active transverse optical phonon modes, which are characterized by a maximum in the imaginary part of the medium’s permittivity. Here, in this Perspective article, we discuss an alternative strategy where the light pulses are instead tailored to match the frequency at which the real part of the medium’s permittivity goes to zero. This so-called epsilon-near-zero regime, popularly studied in the context of metamaterials, naturally emerges to some extent in all dielectric crystals in the infrared spectral range. We find that the light-matter interaction in the phononic epsilon-near-zero regime becomes strongly enhanced, yielding even the possibility of permanently switching both spin and polarization order parameters. We provide our perspective on how this hitherto-neglected yet fertile research area can be explored in future, with the aim to outline and highlight the exciting challenges and opportunities ahead.","PeriodicalId":501713,"journal":{"name":"npj Spintronics","volume":" ","pages":"1-6"},"PeriodicalIF":0.0,"publicationDate":"2024-06-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.nature.com/articles/s44306-024-00025-4.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141246209","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}
npj SpintronicsPub Date : 2024-06-03DOI: 10.1038/s44306-024-00017-4
Kouki Nakata, Kei Suzuki
{"title":"Non-Hermitian Casimir effect of magnons","authors":"Kouki Nakata, Kei Suzuki","doi":"10.1038/s44306-024-00017-4","DOIUrl":"10.1038/s44306-024-00017-4","url":null,"abstract":"There has been a growing interest in non-Hermitian quantum mechanics. The key concepts of quantum mechanics are quantum fluctuations. Quantum fluctuations of quantum fields confined in a finite-size system induce the zero-point energy shift. This quantum phenomenon, the Casimir effect, is one of the most striking phenomena of quantum mechanics in the sense that there are no classical analogs and has been attracting much attention beyond the hierarchy of energy scales, ranging from elementary particle physics to condensed matter physics, together with photonics. However, the non-Hermitian extension of the Casimir effect and the application to spintronics have not yet been investigated enough, although exploring energy sources and developing energy-efficient nanodevices are its central issues. Here we fill this gap. By developing a magnonic analog of the Casimir effect into non-Hermitian systems, we show that this non-Hermitian Casimir effect of magnons is enhanced as the Gilbert damping constant (i.e., the energy dissipation rate) increases. When the damping constant exceeds a critical value, the non-Hermitian Casimir effect of magnons exhibits an oscillating behavior, including a beating one, as a function of the film thickness and is characterized by the exceptional point. Our result suggests that energy dissipation serves as a key ingredient of Casimir engineering.","PeriodicalId":501713,"journal":{"name":"npj Spintronics","volume":" ","pages":"1-6"},"PeriodicalIF":0.0,"publicationDate":"2024-06-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.nature.com/articles/s44306-024-00017-4.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141246228","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}
npj SpintronicsPub Date : 2024-06-03DOI: 10.1038/s44306-024-00021-8
Maxim Mostovoy
{"title":"Multiferroics: different routes to magnetoelectric coupling","authors":"Maxim Mostovoy","doi":"10.1038/s44306-024-00021-8","DOIUrl":"10.1038/s44306-024-00021-8","url":null,"abstract":"The simultaneous presence of ferroelectricity and magnetism in multiferroics breaks both spatial inversion and time reversal symmetries at the macroscopic scale, which opens the door to many interesting phenomena and resembles the violation of these symmetries in particle physics. The symmetry breaking in multiferroics occurs spontaneously at phase transitions rather than at the level of fundamental interactions, and thus can be controlled. Moreover, each crystal is a universe in itself with a unique set of symmetries, coupling constants and ordered patterns, which presents plenty of opportunities to find and design materials with strong magnetoelectric coupling.","PeriodicalId":501713,"journal":{"name":"npj Spintronics","volume":" ","pages":"1-7"},"PeriodicalIF":0.0,"publicationDate":"2024-06-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.nature.com/articles/s44306-024-00021-8.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141246225","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}
npj SpintronicsPub Date : 2024-06-03DOI: 10.1038/s44306-024-00016-5
Vicent J. Borràs, Robert Carpenter, Liza Žaper, Siddharth Rao, Sebastien Couet, Mathieu Munsch, Patrick Maletinsky, Peter Rickhaus
{"title":"A quantum sensing metrology for magnetic memories","authors":"Vicent J. Borràs, Robert Carpenter, Liza Žaper, Siddharth Rao, Sebastien Couet, Mathieu Munsch, Patrick Maletinsky, Peter Rickhaus","doi":"10.1038/s44306-024-00016-5","DOIUrl":"10.1038/s44306-024-00016-5","url":null,"abstract":"Magnetic random access memory (MRAM) is a leading emergent memory technology that is poised to replace current non-volatile memory technologies such as eFlash. However, controlling and improving distributions of device properties becomes a key enabler of new applications at this stage of technology development. Here, we introduce a non-contact metrology technique deploying scanning NV magnetometry (SNVM) to investigate MRAM performance at the individual bit level. We demonstrate magnetic reversal characterization in individual, <60 nm-sized bits, to extract key magnetic properties, thermal stability, and switching statistics, and thereby gauge bit-to-bit uniformity. We showcase the performance of our method by benchmarking two distinct bit etching processes immediately after pattern formation. In contrast to ensemble averaging methods such as perpendicular magneto-optical Kerr effect, we show that it is possible to identify out of distribution (tail-bits) bits that seem associated to the edges of the array, enabling failure analysis of tail bits. Our findings highlight the potential of nanoscale quantum sensing of MRAM devices for early-stage screening in the processing line, paving the way for future incorporation of this nanoscale characterization tool in the semiconductor industry.","PeriodicalId":501713,"journal":{"name":"npj Spintronics","volume":" ","pages":"1-7"},"PeriodicalIF":0.0,"publicationDate":"2024-06-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.nature.com/articles/s44306-024-00016-5.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141246198","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}
npj SpintronicsPub Date : 2024-06-03DOI: 10.1038/s44306-024-00014-7
Ding-Fu Shao, Evgeny Y. Tsymbal
{"title":"Antiferromagnetic tunnel junctions for spintronics","authors":"Ding-Fu Shao, Evgeny Y. Tsymbal","doi":"10.1038/s44306-024-00014-7","DOIUrl":"10.1038/s44306-024-00014-7","url":null,"abstract":"Antiferromagnetic (AFM) spintronics has emerged as a subfield of spintronics, where an AFM Néel vector is used as a state variable. Efficient electric control and detection of the Néel vector are critical for spintronic applications. This review article features fundamental properties of AFM tunnel junctions (AFMTJs) as spintronic devices where such electric control and detection can be realized. We emphasize critical requirements for observing a large tunneling magnetoresistance (TMR) effect in AFMTJs with collinear and noncollinear AFM electrodes, such as a momentum-dependent spin polarization and Néel spin currents. We further discuss spin torques in AFMTJs that are capable of Néel vector switching. Overall, AFMTJs have potential to become a new standard for spintronics providing larger magnetoresistive effects, few orders of magnitude faster switching speed, and much higher packing density than conventional magnetic tunnel junctions (MTJs).","PeriodicalId":501713,"journal":{"name":"npj Spintronics","volume":" ","pages":"1-13"},"PeriodicalIF":0.0,"publicationDate":"2024-06-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.nature.com/articles/s44306-024-00014-7.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141246216","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}
{"title":"2D Magnetic heterostructures: spintronics and quantum future","authors":"Bingyu Zhang, Pengcheng Lu, Roozbeh Tabrizian, Philip X.-L. Feng, Yingying Wu","doi":"10.1038/s44306-024-00011-w","DOIUrl":"10.1038/s44306-024-00011-w","url":null,"abstract":"The discovery of two-dimensional (2D) magnetism within atomically thin structures obtained from layered magnetic crystals has opened up a new realm for exploring magnetic heterostructures. This emerging field provides a foundational platform for investigating unique physical properties and exquisite phenomena at the nanometer and molecular/atomic scales. By engineering 2D interfaces using physical methods and selecting interlayer interactions, we can unlock the potential for extraordinary exchange dynamics, which extends to high-performance and high-density magnetic memory applications, as well as future advancements in neuromorphic and quantum computing. This review delves into recent advances in magnetic 2D materials, elucidates the mechanisms behind 2D interfaces, and highlights the development of 2D devices for spintronics and quantum information processing. Particular focus is placed on 2D magnetic heterostructures with topological properties, promising a resilient and low-error information system. Finally, we discuss the trends of 2D heterostructures for future electronics, considering the challenges and opportunities from physics, material synthesis, and technological perspectives.","PeriodicalId":501713,"journal":{"name":"npj Spintronics","volume":" ","pages":"1-10"},"PeriodicalIF":0.0,"publicationDate":"2024-05-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.nature.com/articles/s44306-024-00011-w.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141182313","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}
npj SpintronicsPub Date : 2024-05-09DOI: 10.1038/s44306-024-00015-6
Nihad Abuawwad, Manuel dos Santos Dias, Hazem Abusara, Samir Lounis
{"title":"Electrical engineering of topological magnetism in two-dimensional heterobilayers","authors":"Nihad Abuawwad, Manuel dos Santos Dias, Hazem Abusara, Samir Lounis","doi":"10.1038/s44306-024-00015-6","DOIUrl":"10.1038/s44306-024-00015-6","url":null,"abstract":"The emergence of topological magnetism in two-dimensional (2D) van der Waals (vdW) magnetic materials and their heterostructures is an essential ingredient for next-generation information technology devices. Here, we demonstrate the all-electric switching of the topological nature of individual magnetic objects emerging in 2D vdW heterobilayers. We show from the first principles that an external electric field modifies the vdW gap between CrTe2 and (Rh, Ti)Te2 layers and alters the underlying magnetic interactions. This enables switching between ferromagnetic skyrmions and meron pairs in the CrTe2/RhTe2 heterobilayer while it enhances the stability of frustrated antiferromagnetic merons in the CrTe2/TiTe2 heterobilayer. We envision that the electrical engineering of distinct topological magnetic solitons in a single device could pave the way for novel energy-efficient mechanisms to store and transmit information with applications in spintronics.","PeriodicalId":501713,"journal":{"name":"npj Spintronics","volume":" ","pages":"1-8"},"PeriodicalIF":0.0,"publicationDate":"2024-05-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.nature.com/articles/s44306-024-00015-6.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140895298","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}
npj SpintronicsPub Date : 2024-05-03DOI: 10.1038/s44306-024-00012-9
Yuzan Xiong, Jayakrishnan M. P. Nair, Andrew Christy, James F. Cahoon, Amin Pishehvar, Xufeng Zhang, Benedetta Flebus, Wei Zhang
{"title":"Magnon-photon coupling in an opto-electro-magnonic oscillator","authors":"Yuzan Xiong, Jayakrishnan M. P. Nair, Andrew Christy, James F. Cahoon, Amin Pishehvar, Xufeng Zhang, Benedetta Flebus, Wei Zhang","doi":"10.1038/s44306-024-00012-9","DOIUrl":"10.1038/s44306-024-00012-9","url":null,"abstract":"The opto-electronic oscillators (OEOs) hosting self-sustained oscillations by a time-delayed mechanism are of particular interest in long-haul signal transmission and processing. On the other hand, owing to their unique tunability and compatibility, magnons—as elementary excitations of spin waves—are advantageous carriers for coherent signal transduction across different platforms. In this work, we integrated an opto-electronic oscillator with a magnonic oscillator consisting of a microwave waveguide and a yttrium iron garnet sphere. We find that, in the presence of the magnetic sphere, the oscillator power spectrum exhibits sidebands flanking the fundamental OEO modes. The measured waveguide transmission reveals anti-crossing gaps, a hallmark of the coupling between the opto-electronic oscillator modes and the Walker modes of the sphere. Experimental results are well reproduced by a coupled-mode theory that accounts for nonlinear magnetostrictive interactions mediated by the magnetic sphere. Leveraging the advanced fiber-optic technologies in opto-electronics, this work lays out a new, hybrid platform for investigating long-distance coupling and nonlinearity in coherent magnonic phenomena.","PeriodicalId":501713,"journal":{"name":"npj Spintronics","volume":" ","pages":"1-7"},"PeriodicalIF":0.0,"publicationDate":"2024-05-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.nature.com/articles/s44306-024-00012-9.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140820730","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}
npj SpintronicsPub Date : 2024-04-29DOI: 10.1038/s44306-024-00019-2
Christopher H. Marrows, Joseph Barker, Thomas A. Moore, Timothy Moorsom
{"title":"Neuromorphic computing with spintronics","authors":"Christopher H. Marrows, Joseph Barker, Thomas A. Moore, Timothy Moorsom","doi":"10.1038/s44306-024-00019-2","DOIUrl":"10.1038/s44306-024-00019-2","url":null,"abstract":"Spintronics and magnetic materials exhibit many physical phenomena that are promising for implementing neuromorphic computing natively in hardware. Here, we review the current state-of-the-art, focusing on the areas of spintronic synapses, neurons, and neural networks. Many current implementations are based on the paradigm of reservoir computing, where the details of the network do not need to be known but where significant post-processing is needed. Benchmarks are given where possible. We discuss the scientific and technological advances needed to bring about spintronic neuromorphic computing that could be useful to an end-user in the medium term.","PeriodicalId":501713,"journal":{"name":"npj Spintronics","volume":" ","pages":"1-7"},"PeriodicalIF":0.0,"publicationDate":"2024-04-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.nature.com/articles/s44306-024-00019-2.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140808223","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}
npj SpintronicsPub Date : 2024-04-25DOI: 10.1038/s44306-024-00010-x
Kyoung-Whan Kim, Byong-Guk Park, Kyung-Jin Lee
{"title":"Spin current and spin-orbit torque induced by ferromagnets","authors":"Kyoung-Whan Kim, Byong-Guk Park, Kyung-Jin Lee","doi":"10.1038/s44306-024-00010-x","DOIUrl":"10.1038/s44306-024-00010-x","url":null,"abstract":"Spin torque is typically classified based on how the spin current is generated and injected into a magnet for manipulation. Spin-orbit torque arises from the spin-orbit interaction in a nearby normal metal, while spin-transfer torque results from exchange interactions in another ferromagnet. Recent studies have suggested that a ferromagnet itself can also generate a spin current through spin-orbit coupling, leading to the emergence of ferromagnet-induced spin-orbit torque as another class of spin torque. This novel torque mechanism not only inherits the advantages of spin-orbit torque architectures, such as separate reading and writing paths in memory applications but also offers the flexibility to control the generated spin direction by manipulating the orientation of the ferromagnet responsible for generating the spin current. In this article, we review the phenomena related to spin currents generated by ferromagnets, explore their physical descriptions in heterostructures, and discuss several spin torque architectures based on this effect. Ferromagnet-induced spin-orbit torque not only introduces new physical consequences by combining spin-orbit and exchange interactions but also offers a promising building block in spintronics with significant potential for diverse applications.","PeriodicalId":501713,"journal":{"name":"npj Spintronics","volume":" ","pages":"1-8"},"PeriodicalIF":0.0,"publicationDate":"2024-04-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.nature.com/articles/s44306-024-00010-x.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140642061","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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