Author
Björn Heinz
Bio: Björn Heinz is an academic researcher from Kaiserslautern University of Technology. The author has contributed to research in topics: Magnonics & Yttrium iron garnet. The author has an hindex of 12, co-authored 26 publications receiving 545 citations.
Topics: Magnonics, Yttrium iron garnet, Spin wave, Magnon, Spin Hall effect
Papers
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TL;DR: A critical width is found, below which the exchange interaction suppresses the dipolar pinning phenomenon and changes the quantization criterion for thespin-wave eigenmodes and results in a pronounced modification of the spin-wave characteristics.
Abstract: Spin waves are investigated in yttrium iron garnet waveguides with a thickness of 39 nm and widths ranging down to 50 nm, i.e., with an aspect ratio thickness over width approaching unity, using Brillouin light scattering spectroscopy. The experimental results are verified by a semianalytical theory and micromagnetic simulations. A critical width is found, below which the exchange interaction suppresses the dipolar pinning phenomenon. This changes the quantization criterion for the spin-wave eigenmodes and results in a pronounced modification of the spin-wave characteristics. The presented semianalytical theory allows for the calculation of spin-wave mode profiles and dispersion relations in nanostructures.
118 citations
TL;DR: The emerging field of magnonics, which utilizes spin waves for data transport and processing, proposes a promis... as discussed by the authors, which is a promising field of research in computer science.
Abstract: Modern-day CMOS-based computation technology is reaching its fundamental limitations. The emerging field of magnonics, which utilizes spin waves for data transport and processing, proposes a promis...
87 citations
TL;DR: In this paper, the authors present a study of the effective magnetization Meff and the effective damping parameter αeff by means of ferromagnetic resonance spectroscopy on the NiFe materials Ni81Fe19 (NiFe) and Co40Fe40B20 (CoFeB) in FM/Pt, FM/NM, and FM/NiFe/Pte systems with the non-magnetic (NM) materials Ru, Cr, Al, and MgO.
Abstract: We present a study of the effective magnetization Meff and the effective damping parameter αeff by means of ferromagnetic resonance spectroscopy on the ferromagnetic (FM) materials Ni81Fe19 (NiFe) and Co40Fe40B20 (CoFeB) in FM/Pt, FM/NM, and FM/NM/Pt systems with the non-magnetic (NM) materials Ru, Cr, Al, and MgO. Moreover, for NiFe layer systems, the influence of interface effects is studied by way of thickness dependent measurements of Meff and αeff. Additionally, spin pumping in NiFe/NM/Pt is investigated by means of inverse spin Hall effect (ISHE) measurements. We observe a large dependence of Meff and αeff of the NiFe films on the adjacent NM layer. While Cr and Al do not induce a large change in the magnetic properties, Ru, Pt, and MgO affect Meff and αeff in different degrees. In particular, NiFe/Ru and NiFe/Ru/Pt systems show a large perpendicular surface anisotropy and a significant enhancement of the damping. In contrast, the magnetic properties of CoFeB films do not have a large influence of t...
69 citations
TL;DR: In this paper, a magnonic directional coupler based on yttrium iron garnet single-mode waveguides of 350 nm width has been proposed to encode information and guide it to one of the two outputs of the coupler depending on the signal magnitude, frequency, and the applied magnetic field.
Abstract: Magnons, the quanta of spin waves, could be used to encode information in beyond-Moore computing applications, and magnonic device components, including logic gates, transistors, and units for non-Boolean computing, have already been developed. Magnonic directional couplers, which can function as circuit building blocks, have also been explored, but have been impractical because of their millimetre dimensions and multi-mode spectra. Here, we report a magnonic directional coupler based on yttrium iron garnet single-mode waveguides of 350 nm width. We use the amplitude of a spin-wave to encode information and to guide it to one of the two outputs of the coupler depending on the signal magnitude, frequency, and the applied magnetic field. Using micromagnetic simulations, we also propose an integrated magnonic half-adder that consists of two directional couplers and processes all information within the magnon domain with aJ energy consumption.
67 citations
TL;DR: In this article, the spin-to-charge current conversion via the inverse spin Hall effect in polycrystalline CoFeB/Pt bilayers and the correlation between the effective spin-mixing conductance and the obtained voltages generated by the spin to charge current conversion was investigated.
Abstract: We investigate spin pumping phenomena in polycrystalline CoFeB/Pt and CoFeB/Ta bilayers and the correlation between the effective spin-mixing conductance ${g}_{\mathrm{eff}}^{\ensuremath{\uparrow}\ensuremath{\downarrow}}$ and the obtained voltages generated by the spin-to-charge current conversion via the inverse spin Hall effect in the Pt and Ta layers. For this purpose, we measure the in-plane angular dependence of the generated voltages on the external static magnetic field and we apply a model to separate the spin pumping signal from the one generated by the spin rectification effect in the magnetic layer. Our results reveal a dominating role of anomalous Hall effect for the spin rectification effect with CoFeB and a lack of correlation between ${g}_{\mathrm{eff}}^{\ensuremath{\uparrow}\ensuremath{\downarrow}}$ and inverse spin Hall voltages pointing to a strong role of the magnetic proximity effect in Pt in understanding the observed increased damping. This is additionally reflected on the presence of a linear dependency of the Gilbert damping parameter on the Pt thickness.
61 citations
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TL;DR: In this paper, the spin degree of freedom of electrons and/or holes, which can also interact with their orbital moments, is described with respect to the spin generation methods as detailed in Sections 2-~-9.
614 citations
Journal Article•
TL;DR: In this article, the linewidth of a series of Permalloy films with thicknesses of 50 and 100nm was measured using linear function of frequency, with a slope that corresponds to a nominal Landau-Lifshitz phenomenological damping parameter α value of 0.007 and zero frequency intercepts in the 160-320A∕m (2-4Oe) range.
Abstract: Stripline (SL), vector network analyzer (VNA), and pulsed inductive microwave magnetometer (PIMM) techniques were used to measure the ferromagnetic resonance (FMR) linewidth for a series of Permalloy films with thicknesses of 50 and 100nm. The SL-FMR measurements were made for fixed frequencies from 1.5to5.5GHz. The VNA-FMR and PIMM measurements were made for fixed in-plane fields from 1.6to8kA∕m (20–100Oe). The results provide a confirmation, lacking until now, that the linewidths measured by these three methods are consistent and compatible. In the field format, the linewidths are a linear function of frequency, with a slope that corresponds to a nominal Landau-Lifshitz phenomenological damping parameter α value of 0.007 and zero frequency intercepts in the 160–320A∕m (2–4Oe) range. In the frequency format, the corresponding linewidth versus frequency response shows a weak upward curvature at the lowest measurement frequencies and a leveling off at high frequencies.
430 citations
University of Grenoble1, Katholieke Universiteit Leuven2, ETH Zurich3, Infineon Technologies4, University of Münster5, University of Gothenburg6, Royal Institute of Technology7, Helmholtz-Zentrum Dresden-Rossendorf8, Kaiserslautern University of Technology9, Université Paris-Saclay10, University of Vienna11, University of York12, University of Lorraine13, Catalan Institution for Research and Advanced Studies14, Spanish National Research Council15, Koç University16, University of Naples Federico II17, University of Messina18, University of Salamanca19
TL;DR: In this article, the potential of spintronics in four key areas of application (memory, sensors, microwave devices, and logic devices) is examined and the challenges that need to be addressed in order to integrate spintronic materials and functionalities into mainstream microelectronic platforms.
Abstract: Spintronic devices exploit the spin, as well as the charge, of electrons and could bring new capabilities to the microelectronics industry However, in order for spintronic devices to meet the ever-increasing demands of the industry, innovation in terms of materials, processes and circuits are required Here, we review recent developments in spintronics that could soon have an impact on the microelectronics and information technology industry We highlight and explore four key areas: magnetic memories, magnetic sensors, radio-frequency and microwave devices, and logic and non-Boolean devices We also discuss the challenges—at both the device and the system level—that need be addressed in order to integrate spintronic materials and functionalities into mainstream microelectronic platforms This Review Article examines the potential of spintronics in four key areas of application —memories, sensors, microwave devices, and logic devices — and discusses the challenges that need be addressed in order to integrate spintronic materials and functionalities into mainstream microelectronic platforms
417 citations
TL;DR: In this article, different approaches for the realization of static, reconfigurable, and dynamic magnonic crystals are presented along with a variety of novel wave phenomena discovered in these crystals.
Abstract: Magnons—the quanta of spin waves—propagating in magnetic materials with wavelengths at the nanometer-scale and carrying information in the form of an angular momentum, can be used as data carriers in next-generation, nano-sized low-loss information processing systems. In this respect, artificial magnetic materials with properties periodically varied in space, known as magnonic crystals, are especially promising for controlling and manipulating the magnon currents. In this article, different approaches for the realization of static, reconfigurable, and dynamic magnonic crystals are presented along with a variety of novel wave phenomena discovered in these crystals. Special attention is devoted to the utilization of magnonic crystals for processing of analog and digital information. Magnonic crystals for data processing 2
353 citations
Max Planck Society1, Catalan Institution for Research and Advanced Studies2, Spanish National Research Council3, Helmholtz-Zentrum Dresden-Rossendorf4, University of Leeds5, University of California, San Diego6, Lawrence Berkeley National Laboratory7, University of California, Santa Cruz8, University of Kiel9, Ikerbasque10, University of Lorraine11, Kaiserslautern University of Technology12, New York University13, University of Nottingham14, Academy of Sciences of the Czech Republic15, Technische Universität Darmstadt16, Daegu Gyeongbuk Institute of Science and Technology17
TL;DR: The 2017 Magnetism Roadmap as mentioned in this paper is the most recent edition of the magnetism roadmap, which is intended to provide a reference point and guideline for emerging research directions in modern magnetism.
Abstract: Building upon the success and relevance of the 2014 Magnetism Roadmap, this 2017 Magnetism Roadmap edition follows a similar general layout, even if its focus is naturally shifted, and a different group of experts and, thus, viewpoints are being collected and presented. More importantly, key developments have changed the research landscape in very relevant ways, so that a novel view onto some of the most crucial developments is warranted, and thus, this 2017 Magnetism Roadmap article is a timely endeavour. The change in landscape is hereby not exclusively scientific, but also reflects the magnetism related industrial application portfolio. Specifically, Hard Disk Drive technology, which still dominates digital storage and will continue to do so for many years, if not decades, has now limited its footprint in the scientific and research community, whereas significantly growing interest in magnetism and magnetic materials in relation to energy applications is noticeable, and other technological fields are emerging as well. Also, more and more work is occurring in which complex topologies of magnetically ordered states are being explored, hereby aiming at a technological utilization of the very theoretical concepts that were recognised by the 2016 Nobel Prize in Physics. Given this somewhat shifted scenario, it seemed appropriate to select topics for this Roadmap article that represent the three core pillars of magnetism, namely magnetic materials, magnetic phenomena and associated characterization techniques, as well as applications of magnetism. While many of the contributions in this Roadmap have clearly overlapping relevance in all three fields, their relative focus is mostly associated to one of the three pillars. In this way, the interconnecting roles of having suitable magnetic materials, understanding (and being able to characterize) the underlying physics of their behaviour and utilizing them for applications and devices is well illustrated, thus giving an accurate snapshot of the world of magnetism in 2017. The article consists of 14 sections, each written by an expert in the field and addressing a specific subject on two pages. Evidently, the depth at which each contribution can describe the subject matter is limited and a full review of their statuses, advances, challenges and perspectives cannot be fully accomplished. Also, magnetism, as a vibrant research field, is too diverse, so that a number of areas will not be adequately represented here, leaving space for further Roadmap editions in the future. However, this 2017 Magnetism Roadmap article can provide a frame that will enable the reader to judge where each subject and magnetism research field stands overall today and which directions it might take in the foreseeable future. The first material focused pillar of the 2017 Magnetism Roadmap contains five articles, which address the questions of atomic scale confinement, 2D, curved and topological magnetic materials, as well as materials exhibiting unconventional magnetic phase transitions. The second pillar also has five contributions, which are devoted to advances in magnetic characterization, magneto-optics and magneto-plasmonics, ultrafast magnetization dynamics and magnonic transport. The final and application focused pillar has four contributions, which present non-volatile memory technology, antiferromagnetic spintronics, as well as magnet technology for energy and bio-related applications. As a whole, the 2017 Magnetism Roadmap article, just as with its 2014 predecessor, is intended to act as a reference point and guideline for emerging research directions in modern magnetism.
317 citations