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The development of skyrmionic devices requires a suitable tuning of material parameters to stabilize skyrmions and control their density. It has been demonstrated recently that different skyrmion types can be simultaneously stabilized at room temperature in heterostructures involving ferromagnets, ferrimagnets, and heavy metals, offering a new platform of coding binary information in the type of skyrmion instead of the presence/absence of skyrmions. Here, we tune the energy landscape of the two skyrmion types in such heterostructures by engineering the geometrical and material parameters of the individual layers. We find that a fine adjustment of the ferromagnetic layer thickness, and thus its magnetic anisotropy, allows the trilayer system to support either one of the skyrmion types or the coexistence of both and with varying densities.

Suicide is a leading cause of death all over the world. Suicide prevention is possible and should be pursued through a variety of strategies. The importance of the arts for positive health outcomes has been increasingly evidenced. This scoping review aimed to identify the possible role of the performing arts—defined as a type of art performed through actions such as music, dance, or drama executed alive by an artist or other participant in the presence of an audience,—in suicide prevention programs. PubMed, Embase, PsycINFO, CINAHL, ProQuest Psychology Database, Scopus, and Web of Science were searched using terms in English for publications of original studies that included performing arts in suicide prevention programs. Thirty-five studies conducted between 1981 and 2021 were identified, of which only five were randomized clinical trials and four quasi-randomized studies. Interventions used different performing arts to improve awareness, self-efficacy, and soft skills relevant to suicide prevention. Studies were addressed mainly to gatekeepers but also directly to at-risk populations. While the study designs do not allow inferences to be drawn about the effectiveness of performing arts in preventing suicide, the review found that performing arts have been successfully implemented in suicide prevention programs. Research to evaluate the possible therapeutic benefit is warranted.

Magneto-optical (MO) effects, viz. magnetically induced changes in light intensity or polarization upon reflection from or transmission through a magnetic sample, were discovered over a century and a half ago. Initially they played a crucially relevant role in unveiling the fundamentals of electromagnetism and quantum mechanics. A more broad-based relevance and wide-spread use of MO methods, however, remained quite limited until the 1960s due to a lack of suitable, reliable and easy-to-operate light sources. The advent of Laser technology and the availability of other novel light sources led to an enormous expansion of MO measurement techniques and applications that continues to this day (see section 1). The here-assembled roadmap article is intended to provide a meaningful survey over many of the most relevant recent developments, advances, and emerging research directions in a rather condensed form, so that readers can easily access a significant overview about this very dynamic research field. While light source technology and other experimental developments were crucial in the establishment of today's magneto-optics, progress also relies on an ever-increasing theoretical understanding of MO effects from a quantum mechanical perspective (see section 2), as well as using electromagnetic theory and modelling approaches (see section 3) to enable quantitatively reliable predictions for ever more complex materials, metamaterials, and device geometries. The latest advances in established MO methodologies and especially the utilization of the MO Kerr effect (MOKE) are presented in sections 4 (MOKE spectroscopy), 5 (higher order MOKE effects), 6 (MOKE microscopy), 8 (high sensitivity MOKE), 9 (generalized MO ellipsometry), and 20 (Cotton-Mouton effect in two-dimensional materials). In addition, MO effects are now being investigated and utilized in spectral ranges, to which they originally seemed completely foreign, as those of synchrotron radiation x-rays (see section 14 on three-dimensional magnetic characterization and section 16 on light beams carrying orbital angular momentum) and, very recently, the terahertz (THz) regime (see section 18 on THz MOKE and section 19 on THz ellipsometry for electron paramagnetic resonance detection). Magneto-optics also demonstrates its strength in a unique way when combined with femtosecond laser pulses (see section 10 on ultrafast MOKE and section 15 on magneto-optics using x-ray free electron lasers), facilitating the very active field of time-resolved MO spectroscopy that enables investigations of phenomena like spin relaxation of non-equilibrium photoexcited carriers, transient modifications of ferromagnetic order, and photo-induced dynamic phase transitions, to name a few. Recent progress in nanoscience and nanotechnology, which is intimately linked to the achieved impressive ability to reliably fabricate materials and functional structures at the nanoscale, now enables the exploitation of strongly enhanced MO effects induced by light-matter interaction at the nanoscale (see section 12 on magnetoplasmonics and section 13 on MO metasurfaces). MO effects are also at the very heart of powerful magnetic characterization techniques like Brillouin light scattering and time-resolved pump-probe measurements for the study of spin waves (see section 7), their interactions with acoustic waves (see section 11), and ultra-sensitive magnetic field sensing applications based on nitrogen-vacancy centres in diamond (see section 17)., Despite our best attempt to represent the field of magneto-optics accurately and do justice to all its novel developments and its diversity, the research area is so extensive and active that there remains great latitude in deciding what to include in an article of this sort, which in turn means that some areas might not be adequately represented here. However, we feel that the 20 sections that form this 2022 magneto-optics roadmap article, each written by experts in the field and addressing a specific subject on only two pages, provide an accurate snapshot of where this research field stands today. Correspondingly, it should act as a valuable reference point and guideline for emerging research directions in modern magneto-optics, as well as illustrate the directions this research field might take in the foreseeable future., Journal of Physics D: Applied Physics, 55 (46), ISSN:0022-3727, ISSN:1361-6463

Reconfigurable magnetization textures offer control of spin waves with promising properties for future low-power beyond-CMOS systems. However, materials with perpendicular magnetic anisotropy (PMA) suitable for stable magnetization-texture formation are characterized by high damping, which limits their applicability in magnonic devices. Here, we propose to overcome this limitation by using hybrid structures, i.e., a PMA layer magnetostatically coupled to a low-damping soft ferromagnetic film. We experimentally show that a periodic stripe-domain texture from a PMA layer is imprinted upon the soft layer and induces a nonreciprocal dispersion relation of the spin waves confined to the low-damping film. Moreover, an asymmetric bandgap features the spin-wave band diagram, which is a clear demonstration of collective spin-wave dynamics, a property characteristic for magnonic crystals with broken time-reversal symmetry. The composite character of the hybrid structure allows for stabilization of two magnetic states at remanence, with parallel and antiparallel orientation of net magnetization in hard and soft layers. The states can be switched using a low external magnetic field; therefore, the proposed system obtains an additional functionality of state reconfigurability. This study offers a link between reconfigurable magnetization textures and low-damping spin-wave dynamics, providing an opportunity to create miniaturized, programmable, and energy-efficient signal processing devices operating at high frequencies., This study has received financial support from the National Science Center of Poland (Projects Nos. UMO-2018/30/Q/ST3/00416, UMO-2018/28/C/ST3/00052, UMO-2019/35/D/ST3/03729, and UMO-2021/41/N/ST3/04478), the Spanish Ministry of Science and Innovation (Project No. PID2019-104604RB/AEI/10.13039/501100011033), and the regional FICYT funding (Grant No. GRUPIN-AYUD/2021/51185) with the support of FEDER funds. The authors acknowledge the technical support provided by Servicios Científico-Técnicos de la Universidad de Oviedo. LMAP and ST acknowledge Italian CNR for financial support from Short Term Mobility Program.

The aim of this review is to highlight the most relevant contributions on dance in neuroscientific research. Neuroscience has analyzed the mirror system through neuroimaging techniques, testing its role in imitative learning, in the recognition of other people's emotions and especially in the understanding of the motor behavior of others. This review analyses the literature related to five general areas: (I) breakthrough studies on the mirror system, and subsequent studies on its involvement in the prediction, the execution, the control of movement, and in the process of “embodied simulation” within the intersubjective relationship; (II) research focused on investigating the neural networks in action observation, and the neural correlates of motor expertise highlighted by comparative studies on different dance styles; (III) studies dealing with the viewer's experience of dance according to specific dance repertoires, which revealed the relevance of choreographic choices for aesthetic appreciation; (IV) studies focused on dance as an aesthetic experience, where both the emotional and the cultural dimension play a significant role, and whose investigation paves the way to further progress both in empirical and in phenomenological research methodologies; (V) collaboration-based experiments, in which neuroscientists and choreographers developed expertise-related questions, especially focusing on the multiple phenomena that underlie motor imagery.

Publisher Copyright: © 2021 The Author(s). Published by IOP Publishing Ltd. Magnonics is a budding research field in nanomagnetism and nanoscience that addresses the use of spin waves (magnons) to transmit, store, and process information. The rapid advancements of this field during last one decade in terms of upsurge in research papers, review articles, citations, proposals of devices as well as introduction of new sub-topics prompted us to present the first roadmap on magnonics. This is a collection of 22 sections written by leading experts in this field who review and discuss the current status besides presenting their vision of future perspectives. Today, the principal challenges in applied magnonics are the excitation of sub-100 nm wavelength magnons, their manipulation on the nanoscale and the creation of sub-micrometre devices using low-Gilbert damping magnetic materials and its interconnections to standard electronics. To this end, magnonics offers lower energy consumption, easier integrability and compatibility with CMOS structure, reprogrammability, shorter wavelength, smaller device features, anisotropic properties, negative group velocity, non-reciprocity and efficient tunability by various external stimuli to name a few. Hence, despite being a young research field, magnonics has come a long way since its early inception. This roadmap asserts a milestone for future emerging research directions in magnonics, and hopefully, it will inspire a series of exciting new articles on the same topic in the coming years.

Background The identical sets of neurons – the mirror neuron system (MNS) – can be activated by simply observing specific, specific movements, decoded behaviors and even facial expressions performed by other people. The same neurons activated during observation are those recruited during the same movements and actions. Hence the mirror system plays a central role in observing and executing movements. Little is known about MNS in a neurodegenerative motor disorder, such as Parkinson’s Disease (PD) is. Methods We explored the neural correlates potentially involved in empathy and embodiment in PD through complex action observation of complex behaviors like the choreutical arts. An integrated multidisciplinary assessment (neurological, neuropsychiatric, and neuropsychological) was used for the selection of the PD candidate for the neuroimaging experimental acquisition. For the first time in literature the famous Calvo-Merino’s paradigm was administered to a PD subject. Key Points Functional magnetic resonance imaging (fMRI) exploratory analysis shows the recruitment of the left thalamus, the right dorsolateral prefrontal cortex, and the bilateral superior precentral gyrus (one of the main hubs of the MNS). If the observed choreic movement becomes part of the observer’s motor repertoire experience, mirror neurons might activate stimulating affective empathy and making the understanding of movement an own proper body experience (cognitive embodiment). Main Lessons Our study sheds light on a possible use of complex action observation to improve or slow the deterioration of motor abilities and levodopa-induced dyskinesias in PD patients. Indeed, the modulation of the neural area involved in complex action observation could be considered a promising target for neuro-rehabilitative intervention mediated by the elicitation of the MNS.

We present the results of a systematic micromagnetic study of the effect of the Dzyaloshinskii-Moriya interaction (DMI) on the spin wave band structure of two one-dimensional magnonic crystals (MCs), both with the same periodicity p = 300 nm, but different implementation of the DMI modulation. In the first system the artificial periodicity was achieved by modulating the interfacial DMI constant D, while in the second system also the sample morphology was modulated. Due to the folding property of the band structure in the dispersion relations of the magnonic crystals it is possible to extend the sensitivity of Brillouin light scattering towards weak DMI strength (D in the range from 0 to 0.5 mJ/m2), by measuring the frequency splitting of folded modes in high-order artificial Brillouin zones, since the splitting increases almost linearly with the band index. For relatively large values of the DMI (D in the range from 1.0 to 2.0 mJ/m2) the spin waves dispersion relations present flat modes for positive wavevectors, separated by forbidden frequency gaps whose amplitude depend on the value of D. These frequency gaps are more pronounced for the sample with morphology modulation. The non-reciprocal, localised, spatial profiles of these modes in both MCs are discussed with reference to spin waves in plain films and in isolated stripes of the same thickness.

Francesco Chillemi’s L’infondamento, an essay on performing arts and literature as a means to approach seminal questions in contemporary philosophical research, extensively deals with the issues of auto-referentiality and self-reflection in the sciences and the humanities. Luigi Pirandello’s Sei personaggi in cerca d’autore, Elsa Morante’s Menzogna e sortilegio and Carmelo Bene’s Amleto (da Shakespeare a Laforgue) are studied as outstanding examples of how artistic creation may “perform” a discourse about itself, and explore epistemological domains usually thought to be open to investigation only by the scientific method. Thus, transdisciplinarity as an “interchange practice”, founded on dialogue and mutual awareness, can help to bridge the gap between different disciplines which nevertheless share the same object of research.

Spin waves propagation in ferromagnetic films, several tens of nanometers thick, have recently received increasing attention, in view of the development of magnonic devices operating in the GHz range of frequencies. A detailed knowledge of the dispersion curves and of the spatial characteristics of the spin-wave modes is preliminary to any technological application, particularly in the ``mesoscopic range'' (50--200 nm) of film thickness, where several dipole-exchange modes may appear in the spectrum, exhibiting frequency crossing and hybridization as a function of their wave number. In this work, the mutual interaction and the hybridization of the dipole-exchange spin-wave modes was investigated in a nitrogen-implanted iron (Fe-N) film, 78-nm-thick, in-plane magnetized. The spin-wave dispersion curves were measured by using Brillouin light scattering, and the experimental results were interpreted combining micromagnetic simulations and theoretical calculations in the framework of a dipole-exchange spin-wave mode approach. A noticeable hybridization between the spin-wave modes was observed, due to the simultaneous presence of a marked perpendicular magnetic anisotropy and a rather high saturation magnetization. The hybridization was found to induce a very large gap ($\mathrm{\ensuremath{\Delta}}\ensuremath{\nu}\ensuremath{\approx}5$ GHz) between the low-frequency spin waves at high wave vector ($k\ensuremath{\approx}{10}^{5}$ rad/cm). Consequently, in such a $k$ range the simultaneous presence of two spin-wave modes with sizeable (${v}_{g}\ensuremath{\approx}1.5$ km/s) but opposite group velocity was observed, opening a way for the potential use of Fe-N films in magnon spintronics.

Topology is known to stabilize rather exotic states in condensed matter and in magneticmaterials. [...]

We report on the study of both perpendicular magnetic anisotropy (PMA) and Dzyaloshinskii-Moriya interaction (DMI) at an oxide/ferromagnetic metal (FM) interface, i.e. BaTiO3 (BTO)/CoFeB. Thanks to the functional properties of the BTO film and the capability to precisely control its growth, we are able to distinguish the dominant role of the oxide termination (TiO2 vs BaO), from the moderate effect of ferroelectric polarization in the BTO film, on the PMA and DMI at the oxide/FM interface. We find that the interfacial magnetic anisotropy energy of the BaO-BTO/CoFeB structure is two times larger than that of the TiO2-BTO/CoFeB, while the DMI of the TiO2-BTO/CoFeB interface is larger. We explain the observed phenomena by first-principles calculations, which ascribe them to the different electronic states around the Fermi level at the oxide/ferromagnetic metal interfaces and the different spin-flip processes. This study paves the way for further investigation of the PMA and DMI at various oxide/FM structures and thus their applications in the promising field of energy-efficient devices., 14 pages, 4 figures, 1 table

In this paper a phenomenological approach, based on a generalization in two dimensions of the classical scalar Preisach model, is exploited and identified to reproduce the magnetization curves obtained by accurate micromagnetic simulations of both isotropic and anisotropic polycrystalline Fe–Si films with different values of the anisotropy constants. The identification problem is realized using a suitable set of analytical equations and performing a best fit procedure to the data obtained from micromagnetic simulations of both scalar and rotational loops. The correct reconstruction of all the magnetization processes, as well as of the associated magnetic losses, is achieved through the choice of a small number of either circular or elliptical hysterons, as well as by the implementation of a simple “moving technique” that is necessary to take into account the non-collinearity between the field and the magnetization that occurs in presence of a global uniaxial anisotropy.

Planar magnetic nanoelements, either single- or multilayered, are exploited in a variety of current or forthcoming spintronic and/or ICT devices, such as read heads, magnetic memory cells, spin-torque nano-oscillators, nanomagnetic logic circuits, magnonic crystals, and artificial spin-ices. The lateral dimensions of the elemental magnetic components have been squeezed down during the last decade to a few tens of nanometers, but they are still an order of magnitude larger than the exchange correlation length of the constituent materials. This means that the spectrum of spin-wave eigenmodes, occurring in the gigahertz range, is relatively complex and cannot be described within a simple macrospin approximation. On the other hand, a detailed knowledge of the dynamical spectrum is needed to understand or to predict crucial characteristics of the devices. With this focused review, we aim at the analysis and the rationalization of the characteristics of the eigenmode spectrum of magnetic nanodots, paying special attention to the following key points: (i) Consider and compare the case of in-plane and out of-plane orientation of the magnetization, as well as of single- and multilayered dots, putting in evidence similarities and diversities, and proposing a unifying nomenclature and labeling scheme; (ii) Underline the evolution of the spectrum when the lateral size of magnetic dots is squeezed down from hundreds to tens of nanometers, as in current devices, with emphasis given to the occurrence of soft modes and to the change of spatial localization of the fundamental mode for in-plane magnetized dots; (iii) Extend the analysis from isolated elements to twins of dots, as well as to dense arrays of dipolarly interacting dots, showing how the discretized eigenmodes distinctive of the single element transform in finite-width frequency bands of spin waves propagating through the array.

Spin waves offer intriguing possibilities for transmitting and processing information in future low-power electronics. Most proposed devices, however, require the efficient excitation and detection of spin waves in the sub-micrometer range, that is a rather challenging task. In fact, coplanar and microstrip waveguides have been widely used in the past to excite and detect spin waves with wavelengths of tens of microns in thin films of both metallic ferromagnets and on magnetic insulators, but the scalability of these structures micrometer or sub-micrometer have not been investigated in detail. In this study, we present a combined experimental/computational study of a few possible input structures consisting of either symmetrical or asymmetrical coplanar waveguides on top of CoFe films, with widths going all the way down to 250 nm. The primary goal of this work is to present a case study, aiming to explore the limitations of waveguides in creating short-wavelength spin waves for future nanoelectronic applications. We use micro-focused Brillouin light scattering measurements and micromagnetic simulations to analyze the characteristics of the emitted spin waves, achieving reasonable agreement between experiment and simulations. We find that due to the inherently delocalized field distributions of waveguides, and also to the relatively high resistivity of narrow waveguides, they all show poor efficiency for generating spin waves with wavelength below about 2 μm, corresponding to frequencies above 10 GHz in a moderate external field. This means that the intensity of the generated spin waves for a given input power drops quickly for the frequency/wavelength range which is most relevant for emerging applications. This case study demonstrates many of the inherent inefficiencies and limitations of waveguide-based spin wave generation in this regime. Our work supports the conclusion that one may have to use a different mechanism for spin wave generation, exploiting multiferroic structures, spin-orbit torques or nanopatterned, multi-layered magnetic materials, all being the subject of intense current research.

Vygotskij’s interest in the arts, and the psychological basis of human response to artworks, was attested by his posthumous book bearing the title of Psychology of Art. There, theatrical problems were barely touched on, and dramatic writing came to the fore. Though, the Soviet psychologist took care to point out that “fifty percent” only of a play can be revealed by its written form, and an extensive research on acting and stage expression was needed to fully understand dramatic meanings. On the Problem of the Psychology of the Actor’s Creative Work briefly summarizes Vygotskij’s concept of the actor’s experience and expression as a peculiar condition of human mental life, whose survey may shed light upon wider questions concerning emotional processes and their connection with the mind-body problem. However, such questions cannot be approached by starting from an exclusive standpoint, be it either naturalistic or cultural, but a methodological attitude is needed that can assimilate – and complement each other – the results of biological, historical and social studies.

We studied the evolution of the magnetic state of a majority logic gate consisting of a cluster of five dipolarly-coupled nanomagnets, fabricated by e-beam lithography, under the application of a clocking field, using a combination of magneto-optical Kerr effect and magnetic force microscopy. The data were interpreted by advanced GPU-based micromagnetic simulations, where, in addition to the single ideal-shaped gate, a 3 × 3 array of “realistic gates”, whose shape is directly derived from scanning electron microscopy images, is considered. A fairly good agreement between measurements and simulations has been achieved, showing that asynchronous switching of nominally identical gates may occur, because of unavoidable structural and morphological imperfections. Moreover, a slight misalignment of 1°−2° of the clocking field with respect to the hard axis of the dots may be detrimental for the correct logic operation of the gates. It follows that reliable, error-free and reproducible operations in future magnetologic devices would require tight control and precision of both the lithographic process and the direction of the clocking field. Moreover, a significant improvement could be insured by a stronger dipolar coupling between the dots, for instance increasing their thickness and/or using materials with larger magnetization.

We present the results of advanced micromagnetic simulations, performed using the open-source GPU-accelerated code MuMax3, on spin waves excitation and propagation in two-dimensional magnonic crystals consisting of Permalloy ( $\text{Ni}_{\text{80}}\text{Fe}_{\text{20}}$ ) square antidot lattices. The magnonic band structure of samples having a fixed periodicity $a = 200\ \text{nm}$ and different sides of the square holes, ranging from 30 to 90 nm, has been analyzed in both the magnetostatic surface wave and backward volume wave configurations, encompassing the first three artificial Brillouin zones. A careful analysis of both the dispersive character and the spatial profile of the most prominent eigenmodes permits interpretation of the main features of the transmission spectra of the simulated samples, which can be considered tunable magnonic filters. General conclusions are drawn about the choice of the optimal geometry for the design of signal processing devices based on square antidot lattices.

In order to achieve better performance of bulk and surface acoustic wave resonators operating at several GHz, it is crucial to dispose of advanced techniques and methods to provide information about the elastic constants of the constituent layered materials and to image the spatial profile of the acoustic field, both inside and outside the resonator.

International audience; The resonant eigenmodes of a nitrogen-implanted iron α'-FeN characterized by weak stripe domains are investigated by Brillouin light scattering and broadband ferromagnetic resonance experiments, assisted by micromagnetic simulations. The spectrum of the dynamic eigenmodes in the presence of the weak stripes is very rich and two different families of modes can be selectively detected using different techniques or different experimental configurations. Attention is paid to the evolution of the mode frequencies and spatial profiles under the application of an external magnetic field, of variable intensity, in the direction parallel or transverse to the stripes. The different evolution of the modes with the external magnetic field is accompanied by a distinctive spatial localization in specific regions, such as the closure domains at the surface of the stripes and the bulk domains localized in the inner part of the stripes. The complementarity of BLS and FMR techniques, based on different selection rules, is found to be a fruitful tool for the study of the wealth of localized magnetic excitations generally found in nanostructures.

Integrated optically inspired wave-based processing is envisioned to outperform digital architectures in specific tasks, such as image processing and speech recognition. In this view, spin waves represent a promising route due to their nanoscale wavelength in the gigahertz frequency range and rich phenomenology. Here, a versatile, optically inspired platform using spin waves is realized, demonstrating the wavefront engineering, focusing, and robust interference of spin waves with nanoscale wavelength. In particular, magnonic nanoantennas based on tailored spin textures are used for launching spatially shaped coherent wavefronts, diffraction-limited spin-wave beams, and generating robust multi-beam interference patterns, which spatially extend for several times the spin-wave wavelength. Furthermore, it is shown that intriguing features, such as resilience to back reflection, naturally arise from the spin-wave nonreciprocity in synthetic antiferromagnets, preserving the high quality of the interference patterns from spurious counterpropagating modes. This work represents a fundamental step toward the realization of nanoscale optically inspired devices based on spin waves.

The propagation of spin waves in antidot lattices with line defects has been studied by both microfocused Brillouin light scattering and micromagnetic simulations. The samples under investigation are NiFe square antidot lattices with circular holes of 250 nm of diameter, periodicity of 700 nm and thickness of 60 nm. Line defects have been introduced in the antidot lattices by removing one row (column) of holes every three rows (columns). Microfocused BLS has been used in order to map out the intensity profile of the main eigenmodes which are excited by a microwave current injected into a coplanar waveguide deposited on top of the sample surface. The comparison between micromagnetic simulations and ?-BLS measurements shows a good agreement not only for the measured frequency but also for the spatial profiles of the modes with the highest intensity in BLS spectra. These eigenmodes extend along the channels between dots rows and their frequency is different in presence of row- or column-defects because of the modification of the internal field felt by the precessing spins. © 2013 Elsevier B.V.

The excitation of spin waves by a microwave current injected into a coplanar waveguide with finite-width ground lines on a continuous Permalloy film is investigated both experimentally and numerically. Phase sensitive micro-focused Brillouin light scattering has been employed to reveal the spatial profile of the propagating spin waves in the magnetostatic surface wave geometry. The experimental results have been satisfactorily reproduced by means of micromagnetic simulations. The exciting microwave field used in this simulation has the spatial profile defined by the coplanar waveguide and user-defined periodic boundary conditions were employed in order to simulate the extended system. The resulting space and time dependent evolution of the magnetization has been analyzed by means of one and two dimensional fast Fourier transform algorithm in order to obtain the spatial profile and the frequency spectrum of the excited spin waves as well as their dispersion relations. Evidence is given to asymmetric emission from the two sides of the coplanar waveguide due to the symmetry breaking related to the sense of precession of the dynamical magnetization, as well as to the near-field effects of the extended spin wave emitter.

Single- or multi-layered planar magnetic dots, with lateral dimensions ranging from tens to hundreds of nanometers, are used as elemental switches in current and forthcoming devices for information and communication technology (ICT), including magnetic memories, spin-torque oscillators and nano-magnetic logic gates. In this review article, we will first discuss energy dissipation during irreversible switching protocols of dots of different dimensions, ranging from a few tens of nanometers to the micrometric range. Then we will focus on the fundamental energy limits of adiabatic (slow) erasure and reversal of a magnetic nanodot, showing that dissipationless operation is achievable, provided that both dynamic reversibility (arbitrarily slow application of external fields) and entropic reversibility (no free entropy increase) are insured. However, recent theoretical and experimental tests of magnetic-dot erasure reveal that intrinsic defects related to materials imperfections such as roughness or polycrystallinity, may cause an excess of dissipation if compared to the minimum theoretical limit. We will conclude providing an outlook on the most promising strategies to achieve a new generation of power-saving nanomagnetic logic devices based on clusters of interacting dots and on straintronics.

Micromagnetic simulations are exploited to analyse the spectrum of dynamical spin eigenmodes in a rectangular MgO-based magnetic tunnel junction (MTJ), with sub-40 nm lateral size, as those exploited in current read heads. It is found that, in spite of the reduced lateral dimensions of this structure, there are several eigenmodes in the range between 0 and 20 GHz, whose frequency and spatial character are markedly dependent on the non-uniformity of the internal field, as well as on the characteristics of the external bias field that is provided by an integrated permanent magnet. The frequency evolution of the modes with the intensity of an additional external field is such that it exists a range of values where the two main eigenmodes of the stack get very close to each other and interchange their preferential localization in the free and reference layers. If one moves from analysis of the small-amplitude magnetization precession to larger amplitude dynamics (precession angles exceeding a few degrees, as it occurs in current MTJ sensors), significant non-linear effects appear in the spectra, such as second harmonics and extra-peaks due to mode mixing. In addition, a sizeable low-frequency tail, that can negatively impact the signal-to-noise ratio of read heads and MTJ sensors, is found in the sub GHz range. These results suggest that a detailed understanding of the dynamical properties of these devices is crucial in order to tailor and optimize their performance.

With read-head structures becoming very small (20°) and cause the appearance of considerable magnetic noise in the read-back function. For instance, the experimental test of a read-head sensor shows that a considerable low-frequency noise appears in the measured signal in coincidence with the superposition of high-frequency eigenmodes of the stack. To shed light on these experimental data, we perform extensive micromagnetic simulations to analyze the spin-wave spectrum of the read-head sensor and its evolution under the application of an external magnetic field. We show that the nonuniformity of both the bias field and the demagnetizing field induces pronounced spatially dependent dynamics within each layer. Moreover, the derived read-back function is characterized by different peaks that reflect the underlying eigenmodes spectrum, as suggested also by simple macrospin approach. However, for large precession amplitude, nonlinear and mixing effects appear, leading to the presence of extra peaks and of a low-frequency tail in the readback signal, in qualitative agreement with experiments.

We have investigated both experimentally and numerically the magnonic band structure of arrays of closely spaced Fe/permalloy nanowires (NWs) with an L-shape cross-section using the Brillouin light scattering technique and GPU-based micromagnetic simulations. NWs consist of a 340 nm wide and 10 nm thick permalloy layer covered by a 170 nm wide Fe overlayer. The thickness of the latter was varied in the range from 0 to 10 nm in order to analyze its influence on the magnonic band structure. We found that both the frequency and the spatial profile of the most intense and dispersive mode, can be efficiently tuned by the presence of the thin Fe NW overlayer. In particular, by increasing the Fe thickness, one observes a substantial frequency increase, while the spatial profile of the mode narrows and moves to the permalloy NW portion not covered by Fe. In addition, the presence of the Fe overlayer causes a significant increase of the number of detected modes and a change of their intensity in the Brillouin spectra as a function of the Bloch wave number. These results show that it is possible to engineer the band structure of magnonic crystals consisting of bi-layered, L-shaped, NWs by a careful control of the overlayer thickness.

The production and the characterization of high-quality ScAlN films, whose electromechanical coupling is larger than those of traditional AlN films, is attracting interest to develop the next generation of bulk acoustic wave resonators for mobile communications. We have exploited the Brillouin light scattering technique (BLS) to achieve a detailed elastic characterization of both AlN and ScAlN films with Sc concentration of 6% and 9.5%. By accurate control of the polarization state of both the incoming and the scattered light, we could detect and identify several distinct acoustic modes, achieving a determination of the whole set of five independent elastic constants and comparing them to recent theoretical predictions based on density functional theory.

1. L’invenzione del dramma in Grecia: i rischi del “gioco” In questa sezione non si intende discutere fonti e documenti sulla nascita del teatro in Occidente, aggiungendo magari nuove ipotesi a un dibattito che, nel corso del tempo, ha evidenziato l’impossibilita di una prosecuzione, una volta riconosciuta l’effettiva assenza di una definita linea genealogica che lega elementi performativi nei riti religiosi e rappresentazioni drammatiche. L’intento principale, qui, e segnalare le peculiarita...