The 2024 Magnonics Roadmap.

Magnonicsis a research field that has gained an increasing interest in both the fundamental and applied sciences in recent years. This field aims to explore and functionalize collective spin excitations in magnetically ordered materials for modern information technologies, sensing applications, and advanced computational schemes. Spin waves, also known as magnons, carry spin angular momenta that allow for the transmission, storage, and processing of information without moving charges. In integrated circuits, magnons enable on-chip data processing at ultrahigh frequencies without the Joule heating, which currently limits clock frequencies in conventional data processors to a few GHz. Recent developments in the field indicate that functional magnonic building blocks for in-memory computation, neural networks, and Ising machines are within reach. At the same time, the miniaturization of magnonic circuits advances continuously as the synergy of materials science, electrical engineering, and nanotechnology allows for novel on-chip excitation and detection schemes. Such circuits can already enable magnon wavelengths of 50 nm at microwave frequencies in a 5G frequency band. Research into non-charge-based technologies is urgently needed in view of the rapid growth of machine learning and artificial intelligence applications, which consume substantial energy when implemented on conventional data processing units. In its first part, the 2024 Magnonics Roadmap provides an update on the recent developments and achievements in the field of nano-magnonics while defining its future avenues and challenges. In its second part, the Roadmap addresses the rapidly growing research endeavors on hybrid structures and magnonics-enabled quantum engineering. We anticipate that these directions will continue to attract researchers to the field and, in addition to showcasing intriguing science, will enable unprecedented functionalities that enhance the efficiency of alternative information technologies and computational schemes.

Design of oscillatory neural networks by machine learning.

We demonstrate the utility of machine learning algorithms for the design of oscillatory neural networks (ONNs). After constructing a circuit model of the oscillators in a machine-learning-enabled simulator and performing Backpropagation through time (BPTT) for determining the coupling resistances between the ring oscillators, we demonstrate the design of associative memories and multi-layered ONN classifiers. The machine-learning-designed ONNs show superior performance compared to other design methods (such as Hebbian learning), and they also enable significant simplifications in the circuit topology. We also demonstrate the design of multi-layered ONNs that show superior performance compared to single-layer ones. We argue that machine learning can be a valuable tool to unlock the true computing potential of ONNs hardware.

Spin-Wave Optics in YIG Realized by Ion-Beam Irradiation.

Direct focused-ion-beam writing is presented as an enabling technology for realizing functional spin-wave devices of high complexity, and demonstrate its potential by optically-inspired designs. It is shown that ion-beam irradiation changes the characteristics of yttrium iron garnet films on a submicron scale in a highly controlled way, allowing one to engineer the magnonic index of refraction adapted to desired applications. This technique does not physically remove material, and allows rapid fabrication of high-quality architectures of modified magnetization in magnonic media with minimal edge damage (compared to more common removal techniques such as etching or milling). By experimentally showing magnonic versions of a number of optical devices (lenses, gratings, Fourier-domain processors) this technology is envisioned as the gateway to building magnonic computing devices that rival their optical counterparts in their complexity and computational power.

Nanoscale neural network using non-linear spin-wave interference.

We demonstrate the design of a neural network hardware, where all neuromorphic computing functions, including signal routing and nonlinear activation are performed by spin-wave propagation and interference. Weights and interconnections of the network are realized by a magnetic-field pattern that is applied on the spin-wave propagating substrate and scatters the spin waves. The interference of the scattered waves creates a mapping between the wave sources and detectors. Training the neural network is equivalent to finding the field pattern that realizes the desired input-output mapping. A custom-built micromagnetic solver, based on the Pytorch machine learning framework, is used to inverse-design the scatterer. We show that the behavior of spin waves transitions from linear to nonlinear interference at high intensities and that its computational power greatly increases in the nonlinear regime. We envision small-scale, compact and low-power neural networks that perform their entire function in the spin-wave domain.

Efficient electromagnetic transducers for spin-wave devices.

This paper presents a system-level efficiency analysis, a rapid design methodology, and a numerical demonstration of efficient sub-micron, spin-wave transducers in a microwave system. Applications such as Boolean spintronics, analog spin-wave-computing, and magnetic microwave circuits are expected to benefit from this analysis and design approach. These applications have the potential to provide a low-power, magnetic paradigm alternative to modern electronic systems, but they have been stymied by a limited understanding of the microwave, system-level design for spin-wave circuits. This paper proposes an end-to-end microwave/spin-wave system model that permits the use of classical microwave network analysis and matching theory towards analyzing and designing efficient transduction systems. This paper further compares magnetostatic-wave transducer theory to electromagnetic simulations and finds close agreement, indicating that the theory, despite simplifying assumptions, is useful for rapid yet accurate transducer design. It further suggests that the theory, when modified to include the exchange interaction, will also be useful to rapidly and accurately design transducers launching magnons at exchange wavelengths. Comparisons are made between microstrip and co-planar waveguide lines, which are expedient, narrowband, and low-efficiency transducers, and grating and meander lines that are capable of high-efficiency and wideband performance. The paper concludes that efficient microwave-to-spin-wave transducers are possible and presents a meander transducer design on YIG capable of launching [Formula: see text]nm spin waves with an efficiency of - 4.45 dB and a 3 dB-bandwidth of 134 MHz.

Experimental demonstration of a concave grating for spin waves in the Rowland arrangement.

We experimentally demonstrate the operation of a Rowland-type concave grating for spin waves, with potential application as a microwave spectrometer. In this device geometry, spin waves are coherently excited on a diffraction grating and form an interference pattern that focuses spin waves to a point corresponding to their frequency. The diffraction grating was created by focused-ion-beam irradiation, which was found to locally eliminate the ferrimagnetic properties of YIG, without removing the material. We found that in our experiments spin waves were created by an indirect excitation mechanism, by exploiting nonlinear resonance between the grating and the coplanar waveguide. Although our demonstration does not include separation of multiple frequency components, since this is not possible if the nonlinear excitation mechanism is used, we believe that using linear excitation the same device geometry could be used as a spectrometer. Our work paves the way for complex spin-wave optic devices-chips that replicate the functionality of integrated optical devices on a chip-scale.

Possible contribution of trained immunity in faulty hormonal imprinting and DOHaD: Review and hypothesis.

The faulty hormonal imprinting theory (published in 1980) and the DOHaD (Developmental Origin of Health and Disease theory (published in 1986) are twin-concepts: both justify the manifestation after long time (in adults) diseases which had been provoked in differentiating cells (e.g. during gestation). This was demonstrated using animal experiments as well, as comparative statistical methods (in human cases). However, there is no explanation for the tools of memorization (even after decades) of the early adversity and the tools of execution (manifestation) in adult age. It seems likely that immune memory is involved to the memorization of early adversity, up to the manifestation of the result (non-communicable diseases). Nevertheless, the relatively short timespan of adaptive immune memory makes this system insuitable for this function, however the newly recognized trained memory of the innate immune system seems to be theoretically suitable for the storage of the records and handling the sequalae, which is the epigenetic reprogramming in the time of provocation, without changes in base sequences (mutation). The flawed (damaged) program is manifested later, in adult age. Evidences are incomplete, so further animal experiments and human observations are needed for justifying the theory.

Programming and reprogramming from conception till death / Programozás és átprogramozás fogamzástól mindhalálig

During conception (fusion of maternal and paternal germ cells) a new entity is formed, which has individual structure and functions. From its gene-pool (genome) epigenetic regulation selects those genes which are durably or acutely working, supplying a theoretically lifelong program. However, this program could be changed spontaneously or artificially, and there are life periods when the spontaneous changes are especially frequent and the sensitivity to physiological or artificial (man-made) factors is high. The basic sensitive (most vulnerable) period is the perinatal one, when the program agglomerated (and this is manifested in the faulty hormonal imprinting and DOHaD theories: perinatal adverse effects can cause diseases in adults), however, later periods are also sensitive. Such rather sensitive periods are the puberty and periadolescence as well as weaning, nevertheless, in any periods of life, cells or cell groups could be epigenetically imprinted, if the cells are in the state of differentiation, independent of the age or developmental state of the complete organism. Earlier mainly natural molecules (products of volcanic eruptions or phytoestrogens, mykotoxins, tobacco) threatened the program, today man-made artificial molecules (endocrine disruptors) can reprogram the visibly stable program, by a single encounter with hormone receptors at the periods of sensitivity (faulty hormonal imprinting) with life-long consequences (altered cell functions, inclination to diseases, manifestation of diseases, etc., provoked by functional teratogens). The deformed program is inherited to the offspring generations, where further program transformations are taking place on the inherited (transformed) program. As the amount and variants of man-made endocrine disruptors are enormously growing in the human environment and its important parts act during the developmentally most sensitive periods, the diseases provoked by them in adults expectedly will be enormously accruing. Orv Hetil. 2020; 161(25): 1028-1034.

Reprogramming of the Immune System by Stress and Faulty Hormonal Imprinting.

PURPOSE: Hormonal imprinting is taking place perinatally at the first encounter between the developing hormone receptors and their target hormones. However, in this crucial period when the developmental window for physiological imprinting is open, other molecules, such as synthetic hormones and endocrine disruptors can bind to the receptors, leading to faulty imprinting with life-long consequences, especially to the immune system. This review presents the factors of stress and faulty hormonal imprinting that lead to reprogramming of the immune system. METHODS: Relevant publications from Pubmed since 1990 were reviewed and synthesized. FINDINGS: The developing immune system is rather sensitive to hormonal effects. Faulty hormonal imprinting is able to reprogram the original developmental program present in a given cell, with lifelong consequences, manifested in alteration of hormone binding by receptors, susceptibility to certain (non-infectious) diseases, and triggering of other diseases. As stress mobilizes the hypothalamic-pituitary-adrenal axis if it occurred during gestation or perinatally, it could lead to faulty hormonal imprinting in the immune system, manifested later as allergic and autoimmune diseases or weakness of normal immune defenses. Hormonal imprinting is an epigenetic process and is carried to the offspring without alteration of DNA base sequences. This means that any form of early-life stress alone or in association with hormonal imprinting could be associated with the developmental origin of health and disease (DOHaD). As puberty is also a period of reprogramming, stress or faulty imprinting can change the original (developmental) program, also with life-long consequences. IMPLICATIONS: Considering the continuous differentiation of immune cells (from blast-cells) during the whole life, there is a possibility of late-imprinting or stress-activated reprogramming in the immune system at any periods of life, with later pathogenetic consequences.

DOHaD: a disease-oriented, epoch-making, British-originated theory with Hungarian roots / [DOHaD (Barker-hipotézis): egy betegségorientált, korszakalkotó, brit eredetu teória, magyar gyökerekkel]

On the basis of comparative epidemiological statistical studies, the 'developmental origin of health and disease' (DOHaD) theory was published in 1986, testifying the interrelation between certain perinatal events, like under- and overfeeding as well as infant mortality with cardiovascular lethality in adults (Barker DJ, Osmond C, Lancet, 1986; 137: 1077­1081) ­ and at present it is widely extended. The theory is rather similar to the hormonal imprinting concept, which had been published 6 years earlier (Csaba G, Biol Rev Cambr Philos Soc. 1980; 55: 47­63 and Horm Metab Res. 1984; 16: 329­335). This demonstrated the role of perinatal encounter with hormones or hormone-like molecules with adult's endocrino-pathological events based on animal experiments. Barker hypothesized the role of hormonal imprinting in DOHaD (Phillips DI, Barker DJ, Osmond C, Acta Endocrinol (Copenh). 1993; 129: 134­138: "A possible explanation is that thyroid hormones present in the breast milk and absorbed by the suckling infant could, by the process of hormonal imprinting, permanently down-regulate the set point of thyroid homeostasis", and this could have encouraged him to create the theory. Both theories suggest the relationship between the perinatal events and adult-age disease manifestation, however, in the case of faulty imprinting, perinatal disease does not have a role in the provocation by imprinters (only the encounter between the imprinter and the hormone receptor), but in the case of DOHaD, this seems to be involved in the process. The whole process points to the disturbance of epigenetic programming. On the basis of the present standpoint, DOHaD is valid in non-communicative diseases, however, considering the impact of faulty hormonal imprinting to the immune system, the extension to communicative diseases is expected and likely also the involvement of lifespan. Further critical developmental period is the adolescence (puberty), when similar reprogramming could be possible and also in certain cases (e.g., in the immune system) disease-causing reprogramming could occur during the whole life. The two concepts are not racing, but using different methods for verification supplement and support each other, by building up identical conclusions (faulty reprogramming) giving epigenetical explanation for numerous diseases. DOHaD and its antecedent, hormonal imprinting are not only theories, but realities, which are commendable to consider in diagnosis and therapy. Studying the tendencies of human creativeness, in all probability, the importance of DOHaD (and faulty imprinting) will be growing in the near and far future. Orv Hetil. 2020; 161(16): 603­609.

[Late manifested sequelae of medications in the critical periods of development. The widening of the faulty hormonal imprinting conception]. / Az egyedfejlodés kritikus fázisaiban történo gyógyszeres kezelések késoi következményei. A hibás hormonális imprinting koncepciójának kiterjesztése.

Hormonal imprinting is a physiological process, which is a part of the receptor-hormone complex development. It determines the binding capacity of the receptors across the lifespan. It takes place perinatally in the critical period of hormone receptor development, when the developmental window for imprinting is open and permits the binding of hormone-like molecules (related or synthetic hormones, endocrine disruptors etc.) causing disturbances of the endocrine system, and the systems- influenced organs by it, for life. This is the faulty hormonal imprinting. However, studying the medical database, PubMed, a lot of data can be found on the harmful late (adult age) effects of medication in the critical period of development with non-hormonal molecules, which are manifested later in functional alterations or diseases. This could mean that in the process of faulty imprinting, the openness of the developmental window could be more important than the structural similarity of a molecule to hormones. As developmentally critical period for faulty imprinting by hormone-like molecules is not exclusively the perinatal one (this is justified in the case of faulty hormonal imprinting), the pubertal period was also studied from this aspect and similarities to the impact of perinatal use have been found (this could be called "Pubertal Origin of Health and Disease = POHaD). While in the case of hormonal faulty imprinting, the mechanism seems to be clear (considering the role of receptors), the mechanism of drug-provoked imprinting is presently uncleared (considering the variety of medications which cause late-manifested alterations). The medicaments-caused faulty imprinting conception calls attention to the dangers of medication in the perinatal as well as the pubertal periods. Orv Hetil. 2020; 161(2): 43-49.

Provocation of life functions at a unicellular eukaryote level by extremely low doses of mammalian hormones: Evidences of hormesis.

Hormones, characteristic to higher ranked animals, are synthesized, stored, and secreted by unicellular eukaryote animals. The unicells also have receptors for recognizing these materials and transmit the message into the cells for provoking response. The hormones are effective in very low concentrations (down to 10-21 M) and opposite effects of lower and higher concentrations can be observed. However, sometimes linear concentration effects can be found, which means that hormesis exists, nevertheless uncertain, as it is in the phase of formation (evolutionary experimentation). Hormesis, by transformation (fixation) of cytoplasmic receptor-like membrane components to receptors in the presence of the given hormone, likely helps the development of unicellular endocrine character and by this the evolution of endocrine system. The effect by extremely low concentrations of hormones had been forced by the watery way of unicellular life, which could establish the physiological concentrations of hormones in the blood of higher ranked animals. This means that hormetic low doses are the normal, effective concentrations and the high concentrations are artificial, consequently could be dangerous.

Magnetization switching using topological surface states.

Topological surface states (TSSs) in a topological insulator are expected to be able to produce a spin-orbit torque that can switch a neighboring ferromagnet. This effect may be absent if the ferromagnet is conductive because it can completely suppress the TSSs, but it should be present if the ferromagnet is insulating. This study reports TSS-induced switching in a bilayer consisting of a topological insulator Bi2Se3 and an insulating ferromagnet BaFe12O19. A charge current in Bi2Se3 can switch the magnetization in BaFe12O19 up and down. When the magnetization is switched by a field, a current in Bi2Se3 can reduce the switching field by ~4000 Oe. The switching efficiency at 3 K is 300 times higher than at room temperature; it is ~30 times higher than in Pt/BaFe12O19. These strong effects originate from the presence of more pronounced TSSs at low temperatures due to enhanced surface conductivity and reduced bulk conductivity.

Aromatic hydrocarbon receptors in the immune system: Review and hypotheses.

Ah-receptors (AhRs) recognize and bind foreign environmental molecules as well as some target hormones of other nuclear receptors. As ligands activate transcription factors, they transmit the information on the presence of these molecules by binding to the DNA, which in turn activate xenobiotic metabolism genes. Cross talk with other nuclear receptors or some non-nuclear receptors also activates or inhibits endocrine processes. Immune cells have AhRs by which they are activated for physiological (immunity) or non-physiological (allergy and autoimmunity) processes. They can be imprinted by hormonal or pseudo-hormonal (environmental) factors, which could provoke pathological alterations for life (by faulty perinatal hormonal imprinting). The variety and amount of human-made new environmental molecules (endocrine disruptors) are enormously growing, so the importance of AhR functions is also expanding.

Hormesis and immunity: A review.

The hormesis concept demonstrates that in contrast to the toxic effect of high doses of materials, irradiation, etc., low doses of them are beneficial and, in addition, help to eliminate (prevent) the deleterious effect of high doses given after it. By this effect, it is an important factor of (human) evolution protecting man from harmful impacts, similarly to the role of immunity. However, immunity is also continuously influenced by hormetic effects of environmental [chemical (pollutions), physical (background irradiations and heat), etc.] and medical (drugs and therapeutic irradiations) and food interactions. In contrast to earlier beliefs, the no-threshold irradiation dogma is not valid in low-dose domains and here the hormesis concept is valid. Low-dose therapeutic irradiation, as well as background irradiations (by radon spas or moderately far from the epicenter of atomic bomb or nuclear facilities), is rather beneficial than destructive and the fear from them seems to be unreasonable from immunological point of view. Practically, all immune parameters are beneficially influenced by all forms of low-dose radiations.

Immunity and longevity.

The role of immune system is to protect the organism from the not built-in program-like alterations inside and against the agents penetrating from outside (bacteria, viruses, and protozoa). These functions were developed and formed during the evolution. Considering these functions, the immune system promotes the lengthening of lifespan and helps longevity. However, some immune functions have been conveyed by men to medical tools (e.g., pharmaceuticals, antibiotics, and prevention), especially in our modern age, which help the struggle against microbes, but evolutionarily weaken the immune system. Aging is a gradual slow attrition by autoimmunity, directed by the thymus and regulated by the central nervous system and pineal gland. Considering this, thymus could be a pacemaker of aging. The remodeling of the immune system, which can be observed in elderly people and centenarians, is probably not a cause of aging, but a consequence of it, which helps to suit immunity to the requirements. Oxidative stress also helps the attrition of the immune cells and antioxidants help to prolong lifespan. There are gender differences in the aging of the immune system as well as in the longevity. There is an advantage for women in both cases. This can be explained by hormonal differences (estrogens positively influences both processes); however, social factors are also not excluded. The endocrine disruptor chemicals act similar to estrogens, like stimulating or suppressing immunity and provoking autoimmunity; however, their role in longevity is controversial. There are some drugs (rapamycin, metformin, and selegiline) and antioxidants (as vitamins C and E) that prolong lifespan and also improve immunity. It is difficult to declare that longevity is exclusively dependent on the state of the immune system; however, there is a parallelism between the state of immune system and lifespan. It seems likely that there is not a real decline of immunity during aging, but there is a remodeling of the system according to the claims of senescence. This is manifested in the remaining (sometimes stronger) function of memory cells in contrast to the production and number of the new antigen-reactive naive T-cells.

Hormonal Imprinting: The First Cellular-level Evidence of Epigenetic Inheritance and its Present State.

Hormonal imprinting takes place perinatally at the first encounter between the developing hormone receptor and its target hormone. This process is needed for the normal function of the receptor-hormone pair and its effect is life-long. However, in this critical period, when the developmental window is open, related molecules (members of the same hormone family, synthetic hormones and hormone-like molecules, endocrine disruptors) also can be bound by the receptor, causing life-long faulty imprinting. In this case, the receptors' binding capacity changes and alterations are caused at adult age in the sexual and behavioral sphere, in the brain and bones, inclination to diseases and manifestation of diseases, etc. Hereby, faulty hormonal imprinting is the basis of metabolic and immunological imprinting as well as the developmental origin of health and disease (DOHaD). Although the perinatal period is the most critical for faulty imprinting, there are other critical periods as weaning and adolescence, when the original imprinting can be modified or new imprintings develop. Hormonal imprinting is an epigenetic process, without changing the base sequence of DNA, it is inherited in the cell line of the imprinted cells and also transgenerationally (up to 1000 generations in unicellulars and up to the 3rd generation in mammals are justified). Considering the enormously growing number and amount of faulty imprinters (endocrine disruptors) and the hereditary character of faulty imprinting, this latter is threatening the whole human endocrine system.

[Possibilities for prolonging human lifespan]. / Az emberi élettartam megnövelésének lehetoségei.

The human lifespan in the developed countries significantly increased, from about 40 years to 80 years, in the last hundred years. This change is due to multiple factors, however, the development of medicine and pharmacological research as well as social well-being and social care are primarily important. For aging, the attrition of the parts of the whole organism are responsible, which is caused by endogenous oxidation processes (free radicals), which can destroy any cells in the organism. The injury of the defense or regulatory organ systems (immune system, neuroendocrine system) influences the whole organism, causing its decline (aging), later complete loss of abilities (death). The organism has built-in mechanisms for defence (e.g., antioxidant enzymes), however, their functions are not enough in our modern, chemically seriously contaminated age and further support is needed. This support is represented by antioxidants, as vitamins A, C, and E, resveratrol, and pharmaceuticals as rapamycine and rapalogs, selegiline, metformin etc., which have important roles in the increase of lifespan and health span. The early start of treatments and the use of pharmaceutical combinations seem to be important. The paper introduces our today's' lifespan prolongers and discusses their effects as well as points to the ways of future development. Orv Hetil. 2018; 159(41): 1655-1663.

Effect of endocrine disruptor phytoestrogens on the immune system: Present and future.

Endocrine disruptors (EDs) are bound by steroid receptors, have steroid-like effects, and by this, negatively influence hormone-regulated processes. Phytoestrogens, which are consumed in enormously high amount by man, are also EDs; however, in contrast to industrial or communal EDs, in some cases have beneficial effects. As immune cells have steroid (first of all, estrogen) nuclear and plasma membrane receptors, which bind phytostrogens (genistein, daidzein, etc.), the development, lifespan, and function of them are deeply influenced by phytoestrogens. They can provoke perinatal faulty hormonal imprinting with lifelong consequences. However, faulty imprinting can be developed not only perinatally but also in other critical periods of life, as weaning, adolescence, and even in continuously dividing cells (e.g., hemopoietic cells) during the whole life. This means that the phytoestrogens could cause direct - instant or long-lasting - steroid effects and durable imprinting effects. As the effect of hormonal imprinting is epigenetically inherited, the phytoestrogen's effects appear in the progeny generations, and the generationally repeated disruptor effects will be different from the present ones. This could also be manifested in the amount, type, and appearance of autoimmune diseases. The consumption of soy is enormously growing, and its immune effect is extended. As the immune system influences basic physiological processes, it seems likely that evolutionary alterations will be observed. In this case, some phytoestrogens will be needed for the normal life of man, as it happened in the case of vitamins A and D, which are already life-important exohormones. However, quantitatively or qualitatively enormous amount of phytoestrogens will cause pathological and epigenetically inherited alterations.