Magnetic Pulse Research Articles

Extreme terahertz magnon multiplication induced by resonant magnetic pulse pairs

Nonlinear interactions of spin-waves and their quanta, magnons, have emerged as prominent candidates for interference-based technology, ranging from quantum transduction to antiferromagnetic spintronics. Yet magnon multiplication in the terahertz (THz) spectral region represents a major challenge. Intense, resonant magnetic fields from THz pulse-pairs with controllable phases and amplitudes enable high order THz magnon multiplication, distinct from non-resonant nonlinearities such as the high harmonic generation by below-band gap electric fields. Here, we demonstrate exceptionally high-order THz nonlinear magnonics. It manifests as 7th-order spin-wave-mixing and 6th harmonic magnon generation in an antiferromagnetic orthoferrite. We use THz two-dimensional coherent spectroscopy to achieve high-sensitivity detection of nonlinear magnon interactions up to six-magnon quanta in strongly-driven many-magnon correlated states. The high-order magnon multiplication, supported by classical and quantum spin simulations, elucidates the significance of four-fold magnetic anisotropy and Dzyaloshinskii-Moriya symmetry breaking. Moreover, our results shed light on the potential quantum fluctuation properties inherent in nonlinear magnons.

Enabling magnetic pulse welding for dissimilar tubular arrester cable joints

AbstractClimate change exacerbates the need for resource-efficient and cost-effective production processes across manifold industries, including the field of electrical connections. This specific field is characterized by a conflict of objectives, i.e., weight reductions while maintaining joint strength and electrical conductivity. From a material point of view, the use of aluminum as a conductor material is suitable for this application, as it is lighter than copper, a classical conductor material. Electrical conductors are often used in the form of flexible cables, so-called stranded wires. This type of conductor as well as the fact that the sole use of aluminum in electrical systems is not feasible, e.g., because the predetermined connection terminals of power electronic components are made of copper, creates a substantial demand for dissimilar aluminum-copper cable arrester joints. However, traditional fusion-based welding processes have proved incapable of reliably producing these dissimilar aluminum-copper joints because of thermophysical effects and chemical incompatibilities, the latter eventually leading to the formation of intermetallic phases. These phases adversely affect the quality of the joint in terms of both mechanical and electrical performance. Yet, magnetic pulse welding, a pressure welding process, is ideally suited for producing dissimilar metal joints on the basis of a low energy input during the welding process. Consequently, the formation of intermetallic phases is restrained. However, magnetic pulse welding has not been sufficiently investigated for the reliable contacting of stranded cables to tubular arresters. As a result, this paper focuses on the fabrication of tubular stranded cable arrester joints using magnetic pulse welding. To shed light on possible material combinations, aluminum-to-aluminum and copper-to-copper joints as well as their dissimilar counterparts are welded. Subsequently, the joints are characterized with regard to their microstructure and quasi-static material strength. Electrical characterization comprises the four-wire Kelvin measurement method to evaluate the resistance of the electrical joints. The results demonstrate that magnetic pulse welding is ideally suited to join the aforementioned material combination and joint configuration due to its process characteristics eventually leading to material continuity. As a result, the stranded wires are welded to the tubular arresters rather than crimped. Consequently, a comparative analysis of the joint properties with those of the joining partners shows that the measured electrical resistances and mechanical tensile forces may be considered very good.

Artificial Intelligence-Powered Pulse Sequences in Nuclear Magnetic Resonance and Magnetic Resonance Imaging: Historical Trends, Current Innovations and Perspectives

This review article explores the historical background and recent advances in the application of artificial intelligence (AI) in the development of radiofrequency pulses and pulse sequences in nuclear magnetic resonance spectroscopy (NMR) and imaging (MRI). The introduction of AI into this field, which traces back to the late 1970s, has recently witnessed remarkable progress, leading to the design of specialized frameworks and software solutions such as DeepRF, MRzero, and GENETICS-AI. Through an analysis of literature and case studies, this review tracks the transformation of AI-driven pulse design from initial proof-of-concept studies to comprehensive scientific programs, shedding light on the potential implications for the broader NMR and MRI communities. The fusion of artificial intelligence and magnetic resonance pulse design stands as a promising frontier in spectroscopy and imaging, offering innovative enhancements in data acquisition, analysis, and interpretation across diverse scientific domains.

Structure and mechanical properties of three-layer composites obtained by magnetic pulse welding of titanium and Zr-based metallic glass

Structure and mechanical properties of three-layer composites obtained by magnetic pulse welding of titanium and Zr-based metallic glass

Does deep TMS really works for smoking cessation? A prospective, double blind, randomized, sham controlled study

Introduction: A substantial proportion of smokers wishing to quit do not stop smoking when using current therapies to aid cessation. Magnetic pulses to specific brain areas designated as transcranial magnetic stimulation may modulate brain activity and thereby change chemical dependencies. Deep transcranial magnetic stimulation (dTMS) with the H4 coil stimulates neuronal pathways in the lateral prefrontal cortex and insula bilaterally, areas involved in tobacco addiction. Objective: To evaluate the efficacy and safety of dTMS with T4 coil in smoking cessation. Methods: In a double blind, controlled clinical trial, adult smokers of at least 10 cigarettes/day were randomized to active (n = 50) versus sham dTMS (n = 50). The protocol involved up to 21 sessions administered over up to 12 weeks. Tobacco use was monitored by self-report and confirmed by expired air monoximetry (at each dTMS visit) and blood cotinine (at the screening visit and at the end of sessions). Participants completed abstinence, mood and cognition scales at determined timepoints during follow-up. Results: In the intention to-treat-analysis, the cessation rate of the intervention and control groups was 14.0%. The reported side effects were as expected for this procedure. Although there were no serious adverse events, three participants were withdrawn according to safety criteria. Conclusion: Active treatment with dTMS H4 coil was safe but not effective for smoking cessation.

Variable repetition rate pulse power supply based on magnetic pulse compression for copper vapor lasers

Variable repetition rate pulse power supply based on magnetic pulse compression for copper vapor lasers

Mechanical Behaviors of Polymer-Based Composite Reinforcements within High-Field Pulsed Magnets.

The development of pulsed magnets capable of generating magnetic fields exceeding 100 Tesla has been recognized as a crucial pursuit for advancing the scientific research on high magnetic fields. However, the operation of magnets at ultra-high magnetic fields often leads to accidental failures at their ends, necessitating a comprehensive exploration of the underlying mechanisms. To this end, this study investigates, for the first time, the mechanical behaviors of Zylon fiber-reinforced polymers (ZFRPs) within pulsed magnets from a composite perspective. The study begins with mechanical testing of ZFRPs, followed by the development of its constitutive model, which incorporates the plasticity and progressive damage. Subsequently, in-depth analyses are performed on a 95-T double-coil prototype that experienced a failure. The outcomes reveal a notable reduction of approximately 45% in both the radial and axial stiffness of ZFRPs, and the primary reason for the failure is traced to the damage incurred by the end ZFRPs of the inner magnet. The projected failure field closely aligns with the experiment. Additionally, two other magnet systems, achieving 90.6 T and 94.88 T, are analyzed. Finally, the discussion delves into the impact of transverse mechanical strength of the reinforcement and axial Lorentz forces on the structural performance of magnets.

Review of High Voltage Pulsed Power Supplies and Power Electronics in Pulse Power Generation

Recently, pulse-shaped power supplies have become more popular. Pulsed power is versatile and useful as a supply method since it can take several shapes and has many pulse characteristics. The release of electrons, protons, and neutrons from an atom and the synthesis of molecules to generate ions or other molecules require a lot of immediate energy. Pulsed power is needed for decomposition, molecular fusion and material joining, radiation generation (e.g., electrons, lasers, radar), explosive processes for concrete recycling, wastewater and exhaust gas treatment, and material surface treatments. Industrial and environmental applications require pulsed power, which requires efficient and adaptive pulse modulators. Higher-quality repeating pulses are needed for plasma fusion and laser weapons. Marx Generators, Magnetic Pulse Compressors, Pulse Forming Networks, and Multistage Blumlein Lines have several uses. Pulse modulators use spark gap and hydrogen thyratron gas/magnetic switching technologies for their high voltage tolerance and low-rise times. These creatures are inefficient, unreliable, repetitious, and short-lived. These devices are heavy, bulky, and expensive. Solid-state switching technology can replace conventional devices, improving pulse supply. High-frequency switching repeats the pulsed power supply. These items are compact, efficient, affordable, reliable, and durable. Solid-state transistor applications may not meet switch voltage ratings and rise time constraints. Various power electronics configurations can produce solid-state high-voltage pulses.

Technique for Selecting Control Decisions in Optimizing Technological Modes of Processing Iron Ore Raw Materials Using Electromagnetic Influences

Purpose of reseach. The paper considers the process of selective pre-destruction of interphase boundaries in iron ores by using magnetic-pulse treatment. When analyzing the stress-strain state and viscous fracture, the relative similarity of the fracture criteria in the main minerals of iron ores due to magnetically-striction deformation of magnetite grains. Methods.It has been established that the strength and toughness of the destruction of magnetite exceeds the analogous properties of calcite in the composition of skarn iron ores, the strength and toughness of quartz fracture exceeds the analogous properties of magnetite. A difference in the character of the destruction of skarn ores and ferruginous quartzites. The criterion for estimating the degree of softening of interphase boundaries in iron ores due to the magnetic-impulse action based on the probabilistic approach is formulated. Results.A theoretical estimate is made of the degree of selective softening of iron ores under magnetic-pulse treatment, taking into account the strength and magnetostriction properties of magnetite. The results of experiments on nanoindentation of interphase boundaries before and after magnetic-pulse processing are presented. Conclusion. By analyzing the lengths of developing microcracks under the influence of a nanoindenter, the possibility of reducing the fracture toughness after a magnetic pulse treatment of iron ore.

Optoelectronic–thermomagnetic effect of a microelongated non-local rotating semiconductor heated by pulsed laser with varying thermal conductivity

Abstract In this study, we investigated the effect of a rotation field and magnetic field on a homogeneous photo-thermoelastic nonlocal material and how its thermal conductivity changes as a result of a linearly distributed thermal load. The thermal conductivity of an interior particle is supposed to increase linearly with temperature under the impact of laser pulses. Microelastic (microelements distribution), non-local semiconductors are used to model the problem under optoelectronic procedures, as proposed by the thermoelasticity theory. According to the microelement transport processes, the micropolar-photo-thermoelasticity theory accounts for the medium’s microelongation properties. This mathematical model is solved in two dimensions using the harmonic wave analysis. Non-local semiconductor surfaces can generate completely dimensionless displacement, temperature, microelongation, carrier density, and stress components with the appropriate boundary conditions. The effects of thermal conductivity, thermal relaxation times, magnetic pressure effect, laser pulses, and rotation parameters on wave propagation in silicon (Si) material are investigated and graphically displayed for a range of values.

Magneto‐Responsive Bistable Structures with Rate‐Dependent Actuation Modes

AbstractStructural instabilities can be used to provide rapid responses activated by mechanical force or displacement thresholds. The emergence of responsive materials has opened the door for adapting such structural instabilities to actuators that will abruptly deform guided by external stimuli. However, fast configurational transitions between equilibrium states imply important viscoelastic roles at the material level that inevitably scale up to the structural level. A comprehensive understanding of viscoelastic effects is provided on bistable structural transitions combining a new experimental perspective and a thorough modeling analysis. The insights from these results are here translated to magneto‐responsive bistable structures offering a route‐map to design effective actuation conditions. The bistable transition functionally depends on the combination of magnetic field amplitude and application rate. The understanding of the viscoelastic and magneto‐mechanical coupling provides efficient actuation via temporal magnetic pulses, removing the need of generating continued magnetic fields. Finally, these insights are combined to develop a responsive structure whose transient and steady bistable transitions can be modulated by the application rate of external magnetic stimuli.

Observation of pinning and pinning evasion dynamics of a magnetic vortex core

An understanding of the dynamics of magnetic textures as they interact with defects in the host material is critical for proposed applications that depend on controlled translation of these magnetic textures. We report on the experimental observation of magnetic vortex core (VC) trajectories as they are affected by a potential energy landscape arising from defects in thin, permalloy disks. We first map the VC pinning landscape using equilibrium Kerr microscopy, and then use multiplexed time-resolved Kerr microscopy to track in-plane dynamics of a magnetic VC in response to a magnetic field pulse with ns time resolution, and several-nm spatial resolution. The initial position of the VC is set by applying a static magnetic field to shift the dynamics relative to the pinning landscape. We observe the expected spiral trajectory as the VC relaxes to equilibrium over several tens of nanoseconds. However, in the presence of strong pinning, we also observe pinning evasion as the VC trajectory is deflected due to the pinning potential, and enhanced damping as the vortex becomes pinned. We compare to a simple model based on the Thiele equation of motion to understand these results.

Control of the memory cell magnetization by a combined pulse of local magnetic fields

We study the process of controlling the states of a magnetic memory cell by a pulsed magnetic field. The magnetization dynamics of such a system is described by the Landau-Lifshitz equation. We find the optimal parameters of time dependence, amplitude and duration of magnetic field pulses created by currents in the control system, which provide a fast inertialess process of switching the magnetization of the functional element of the cell.

Birthplace of ball lightning

Examples of ball lightning formation at high altitude near a linear lightning channel are considered. A photograph of ball lightning emerging from a linear lightning channel is shown. It is shown that the process of ball lightning formation lasts no more than 30 ms. A model of ball lightning formation due to the action of a magnetic field pulse of a linear lightning current on the ionized volume of space is described. A scheme has been proposed to explain a rare event - the gathering of ball lightning from sparks. Cases of the formation of ball lightning at a large distance from the site of a linear lightning strike, when energy was transferred through wires, are considered. It is noted that the process of formation of such ball lightning and their properties differ markedly from ball lightning appearing near the channel of linear lightning. This made it possible to distinguish these objects into a special type of ball lightning. A model of the process of formation of such ball lightning is described, according to which their core consists of ions flowing from the electrode of an air electrical capacitor (antenna, power line), and the shell material is dust particles. Cases of observation of objects with a size of 50 microns - 1 mm appearing during electrical discharges in water are considered. The analogy of these objects with miniature ball lightning is shown.

Tesla-class single-cycle terahertz magnetic field pulses generated with a spiral-shaped metal microstructure

Abstract We study the terahertz (THz) magnetic field pulse enhanced by a spiral-shaped antenna resonator (SAR). We deposit the SAR on the surface of a terbium-gallium-garnet crystal, which has a large Verdet constant, and measure the Faraday rotation angle for strong THz pulse excitation by magneto-optical sampling (MOS) with near-infrared light. The determined magnetic field strength and field-enhancement spectrum are consistent with the theoretical predictions. This first report of the detection of the magnetic field of a Tesla-class picosecond pulse by magneto-optical sampling is expected to be useful in research on the control of magnetization in spintronic devices.

Design of field shaper suitable for plate and experimental research on welding of dissimilar materials

Magnetic pulse welding realizes solid-state connection through a high-speed collision of materials, which can effectively overcome the welding difficulties of light metal materials. In the magnetic pulse welding system, in order to improve the welding efficiency, a field shaper is usually applied between the multi-turn coil and the workpiece to concentrate the magnetic field in the welding area, thereby improving the electromagnetic force. However, a large number of researchers are currently on the tube-welded field shaper, and very few researchers have studied the structure of the plate-welded field shaper. Therefore, this paper proposed a new field shaper for plate welding. The effect of the structure parameter of the field shaper on the magnetic field and electromagnetic force on the aluminum plate was analyzed in the COMSOL multiphysics software. The optimal structure parameters of the field shaper were selected. The plastic deformation and the generation of jets under different voltages and the welding of the same/dissimilar metal materials at different standoff distances were studied experimentally, which verifies the feasibility of the new field shaper.

Gradient of nanostructures at the interface of Al/Cu welded joints produced by the high strain-rate collision during magnetic pulse impact welding

This paper focuses on the nanoscale characterization of a welded Al/Cu interface produced by magnetic pulse welding. Welding tests were performed using three field shapers with similar dimension but having strongly different electrical conductivity. Other welding parameters were strictly the same. The three tests produce similar welded joints that consist of a similar morphology of wavy interface at the macroscopic scale. Thus, the Al to Cu transition zone across the location of an interfacial wave is identified as a suitable repetitive site that enables for repetitive fine-scale characterization across a distance less than 1 µm. Transmission Electron Microscopy (TEM) observations of the welded Al/Cu interface reveal a gradient of nanostructures which consists of an amorphous AlxCuy nanolayer (∼30 nm) and then, a nanocrystalline layer with a thin thickness of a few tens of nanometres at the Cu side and at the Al side as well. This hierarchical nano-featured structure is confined within a very short total distance of about 200 nm. Outside these confined nanostructures, the interface exhibits a crystalline structure. These nanofeatures were observed at the interface of the Al/Cu welded joint produced by three different field shapers, that shows a reproducibility of the interface structure at the nanoscale level. A thermomechanical analysis of the high strain process at a collision point allows for depicting the mechanism of microstructure formation confined at the Al/Cu interface. The shear strain rate across the interface shows peaks where the temperature distribution also reaches a peak beyond the melting point of Al. The thermal kinetics within the molten zone is characterized by a high cooling rate up to 103 °C/ns during the melting/solidification stage that explains the observation of the amorphous nanolayer revealed by the TEM observation. The formation of nanocrystalline structure confined at both sides of the amorphous layer can be explained by a nucleation of crystals at a very early stage governed by the thermal kinetics at the boundaries (Al side and Cu side) of the melted zone, and by a dynamic recrystallization governed by the gradient of shearing at high strain rate confined at the collision point. Together, these processes of highly transient thermomechanical responses confined at the Al/Cu interface explain the formation mechanism of interface microstructure that results in the hierarchical nanostructure as identified by TEM characterizations.

Energy efficiency improvement method of magnetic pulse welding based on auxiliary capacitance

Energy efficiency improvement method of magnetic pulse welding based on auxiliary capacitance

Magnetic properties and magnetocaloric effect of DyCo9Si4

Polycrystalline samples of DyCo9Si4 with the tetragonal LaFe9Si4-type structure have been synthesized by arc melting and high-temperature annealing. Results of the magnetization M and specific heat Cp measurements show the existence of two magnetic anomalies at TC = 40 K and Tm = 20 K. The transition at TC = 40 K is attributed to the ferromagnetic transition of the Co sublattice. The magnetic moments of Dy3+ appear to align gradually below TC, and almost fixed below Tm, at which a broad maximum in Cp has been observed. Field-dependent M at T = 2 K up to H = 7 T suggested that the magnetic moment of Dy3+ is coupled antiferromagnetically with those of Co, forming a ferrimagnetic structure. Magnetization measurements up to 50 T at low temperatures using a pulse magnet demonstrated a spin-flip transition around H = 20 T, above which the magnetic moments of Co and Dy are in parallel. The spin-flip transition becomes broad with increasing temperature but still remains at TC = 40 K, indicating a strong antiparallel coupling between Co and Dy moments even in the paramagnetic state. The magnetocaloric effect was evaluated from Cp and M, and also from the sample-temperature variation in the quasi-adiabatic process with the pulsed magnetic field. The maximum entropy change for the field change from 5 to 0 T was observed at around T = Tm with the value ΔS = 5 J/kg K. The maximum temperature of ΔS shifts to higher temperatures in high magnetic fields, resulting in the large value of ΔS = 24 J/kg K at T ∼ TC by the field change from 50 to 0 T. The present results demonstrate that the pulsed-field measurement is a powerful method to evaluate the magnetocaloric effect of materials.

Relation between task-related activity modulation and cortical inhibitory function in schizophrenia and healthy controls: a TMS-EEG study.

Schizophrenia has been associated with a reduced task-related modulation of cortical activity assessed through electroencephalography (EEG). However, to the best of our knowledge, no study so far has assessed the underpinnings of this decreased EEG modulation in schizophrenia. A possible substrate of these findings could be a decreased inhibitory function, a replicated finding in the field. In this pilot study, our aim was to explore the association between EEG modulation during a cognitive task and the inhibitory system function in vivo in a sample including healthy controls and patients with schizophrenia. We hypothesized that the replicated decreased task-related activity modulation during a cognitive task in schizophrenia would be related to a hypofunction of the inhibitory system. For this purpose, 27 healthy controls and 22 patients with schizophrenia (including 13 first episodes) performed a 3-condition auditory oddball task from which the spectral entropy modulation was calculated. In addition, cortical reactivity-as an index of the inhibitory function-was assessed by the administration of 75 monophasic transcranial magnetic stimulation single pulses over the left dorsolateral prefrontal cortex. Our results replicated the task-related cortical activity modulation deficit in schizophrenia patients. Moreover, schizophrenia patients showed higher cortical reactivity following transcranial magnetic stimulation single pulses over the left dorsolateral prefrontal cortex compared to healthy controls. Cortical reactivity was inversely associated with EEG modulation, supporting the idea that a hypofunction of the inhibitory system could hamper the task-related modulation of EEG activity.