Pulsed Magnetic Field Research Articles

Changes in the activity of micromycete endocellular oxidoreductases under the influence of low-frequency pulsed magnetic field and low-intensity laser radiation

This study aims to investigate the effects of low-frequency pulsed magnetic field (1.5 Hz) and low-intensity laser radiation (0.3 and 0.7 W) on the activity of micromycete endocellular oxidoreductases that catalyze biodegradation of industrial materials such as Penicillium cyclopium, Aspergillus niger, and Alternaria alternata. The investigated physical factors had dose-dependent effects on the activity of fungal endocellular oxidoreductases (catalase and peroxidase): increases and decreases in the activities of enzymes have been observed. An increase in the activity of enzymes can contribute to the manifestation of the adaptive properties of fungi against the action of such physical factors as low-intensity laser radiation and magnetic field. A decrease in the activity of endocatalase and endoperoxidase under the influence of these factors may suppress the vital activity of microorganisms.

Cations impact radical reaction dynamics in concentrated multicomponent aqueous solutions.

Ultraviolet (UV) photolysis of nitrite ions (NO2-) in aqueous solutions produces a suite of radicals, viz., NO·, O-, ·OH, and ·NO2. The O- and NO· radicals are initially formed from the dissociation of photoexcited NO2-. The O- radical undergoes reversible proton transfer with water to generate ·OH. Both ·OH and O- oxidize the NO2- to ·NO2 radicals. The reactions of ·OH occur at solution diffusion limits, which are influenced by the nature of the dissolved cations and anions. Here, we systematically varied the alkali metal cation, spanning the range from strongly to weakly hydrating ions, and measured the production of NO·, ·OH, and ·NO2 radicals during UV photolysis of alkaline nitrite solutions using electron paramagnetic resonance spectroscopy with nitromethane spin trapping. Comparing the data for the different alkali cations revealed that the nature of the cation had a significant effect on production of all three radical species. Radical production was inhibited in solutions with high charge density cations, e.g., lithium, and promoted in solutions containing low charge density cations, e.g., cesium. Through complementary investigations with multinuclear single pulse direct excitation nuclear magnetic resonance (NMR) spectroscopy and pulsed field gradient NMR diffusometry, cation-controlled solution structures and extent of NO2- solvation were determined to alter the initial yields of ·NO and ·OH radicals as well as alter the reactivity of NO2- toward ·OH, impacting the production of ·NO2. The implications of these results for the retrieval and processing of low-water, highly alkaline solutions that comprise legacy radioactive waste are discussed.

Magnetoresistance and Magnetic Relaxation of La-Sr-Mn-O Films Grown on Si/SiO2 Substrate by Pulsed Injection MOCVD

The results of magnetoresistance (MR) and resistance relaxation of nanostructured La1−xSrxMnyO3 (LSMO) films with different film thicknesses (60–480 nm) grown on Si/SiO2 substrate by the pulsed-injection MOCVD technique are presented and compared with the reference manganite LSMO/Al2O3 films of the same thickness. The MR was investigated in permanent (up to 0.7 T) and pulsed (up to 10 T) magnetic fields in the temperature range of 80–300 K, and the resistance-relaxation processes were studied after the switch-off of the magnetic pulse with an amplitude of 10 T and a duration of 200 μs. It was found that the high-field MR values were comparable for all investigated films (~−40% at 10 T), whereas the memory effects differed depending on the film thickness and substrate used for the deposition. It was demonstrated that resistance relaxation to the initial state after removal of the magnetic field occurred in two time scales: fast’ (~300 μs) and slow (longer than 10 ms). The observed fast relaxation process was analyzed using the Kolmogorov–Avrami–Fatuzzo model, taking into account the reorientation of magnetic domains into their equilibrium state. The smallest remnant resistivity values were found for the LSMO films grown on SiO2/Si substrate in comparison to the LSMO/Al2O3 films. The testing of the LSMO/SiO2/Si-based magnetic sensors in an alternating magnetic field with a half-period of 22 μs demonstrated that these films could be used for the development of fast magnetic sensors operating at room temperature. For operation at cryogenic temperature, the LSMO/SiO2/Si films could be employed only for single-pulse measurements due to magnetic-memory effects.

Magnetic-field-induced valence change in Eu(Co1−xNix)2P2 up to 60 T

The solid solution 122 compounds, $\mathrm{Eu}{({\mathrm{Co}}_{1\ensuremath{-}x}{\mathrm{Ni}}_{x})}_{2}{\mathrm{P}}_{2}$, show a valence transition between divalent state and intermediate valence states at Eu, which is firmly correlated to multiple degrees of freedom in the solid such as the isostructural transition between the collapsed tetragonal (cT) and uncollapsed tetragonal (ucT) structures, $3d$ magnetism, and the formation of P-P dimers. To gain insights into the correlated behavior, we investigate the effect of high magnetic fields on the samples of $x=0.4$ and 0.5 using magnetostriction and magnetization measurements up to 60 T. The samples are in the Eu valence-fluctuating regime, where the possible structural transition from cT to ucT may be induced by the Eu valence change under the magnetic fields. For both samples, magnetostriction smoothly increases with increasing magnetic fields. The behavior is in good agreement with the calculated results using the interconfigurational fluctuation (ICF) model that describes the Eu valence change. This indicates that $\mathrm{\ensuremath{\Delta}}L$ represents the change of the Eu valence state in these compounds. Magnetization curves for both compounds show good agreement with the ICF model at high magnetic fields. In contrast, in the low-magnetic-field region, magnetization curves do not agree with the ICF model. These results indicate that the Eu valence changes manifest themselves in the magnetization curves at high magnetic fields and that the magnetism of the $3d$ electrons manifests itself in the magnetization at low magnetic fields. Hence, we conclude that the valence change occurs within the Eu valence fluctuation regime coupled with the cT structure. Thereby, we believe that the transition to ucT structure, which is firmly coupled with the divalent Eu state, does not occur within the magnetic field range of the present study. Even higher magnetic fields or pulsed magnetic fields with slower pulse durations may induce such large state changes in the present material, which is triggered by the Eu valence change under high magnetic fields.

Field induced phase transition and magnetic phase diagram of multiferroic Ca2CoSi2O7

Magnetic phase transitions are important for the application of individual materials toward modern spintronics and sensing. Using high-resolution sound velocity and pyrocurrent measurements, we have obtained a detailed magnetic phase diagram of multiferroic Ca2CoSi2O7 for magnetic fields applied along the crystallographic [100]- and [001]-directions. The magneto-acoustic measurements were conducted for both longitudinal and transverse modes in both static and pulsed magnetic fields up to 17 and 68 T, respectively. Distinct anomalies with significant changes in sound velocity and sound attenuation were observed at the onset of the structural and magnetic phase transitions. Interestingly, results obtained for fields parallel to the [100]-direction reveal a hysteresis and step-like decrements in ultrasound indicating a transition into a different metastable structural distortion below TN and at magnetic fields between 4 and 10 T that has not been previously reported. We believe that this field-induced distorted structure phase may be the cause of the subsequent phase transition at 11 T. At low temperatures, a softening of the lattice within the ordered phases is also observed, which may be due to residual spin fluctuations.

Efficient scheme for time-dependent thermal pure quantum state: Application to the Kitaev model with armchair edges

We consider the time-dependent thermal pure quantum state method and introduce the efficient scheme to evaluate the change in physical quantities induced by the time-dependent perturbations, which has been proposed in our previous paper [H. Taguchi et al., Phys. Rev. B 105, 125137 (2022)]. Here, we treat the Kitaev model to consider the Majorana-mediated spin transport, as an example. We demonstrate how efficient our scheme is to evaluate spin oscillations induced by the magnetic field pulse.

High field magnetism of the triangular lattice antiferromagnet CsFeCl$_3$ under high pressure

Magnetization measurements of the triangular lattice antiferromagnet CsFeCl_{3}3 at 1.4 K for H \parallel cH∥c were performed in pulsed high magnetic fields of up to 51 T under high pressures of up to 0.80 GPa. At ambient pressure, the magnetization below H_{c1}Hc1 = 4 T is small, and then it changes steeply between H_{c1}Hc1 and H_{c2}Hc2 = 12 T, followed by a gradual increase in magnetization up to H_{m}Hm = 33 T where a two-step metamagnetic transition occurs. With increasing pressure, the H_{c1}Hc1 and H_{m}Hm shifted to the low-field side, while the H_{c2}Hc2 shifted to the opposite side. The change in H_{m}Hm may depend on the difference in the single-ion anisotropies on pressure in the lowest JJ = 1 and the excited J=2J=2 states.

Application of high-intensity pulsed magnetotherapy in the medical rehabilitation of children with degree scoliose (methodological recommendations)

In the medical rehabilitation of children with scoliosis, a fairly wide range of physiotherapy technologies (sinusoidal modulated currents, interference currents, laser therapy, combined use of hypobarotherapy and electrical muscle stimulation, low-intensity magnetic therapy, biofeedback therapy) are used. At the same time, the search for the most effective methods of physiotherapy aimed at stimulating muscle tone, local blood circulation and metabolic and trophic processes in bone and muscle tissues continues. One of the promising methods is high-intensity pulsed magnetic therapy (HIMT), which is a therapeutic effect of a pulsed magnetic field (PMF) with a pulse repetition rate of about 0.5 Hz, a duration not exceeding several milliseconds and an amplitude reaching 1500 mT or more on the working surface of the inductor. The guidelines substantiate the use of this method in the medical rehabilitation of children with scoliosis of the II degree on the basis of the revealed favorable effect of a high-intensity pulsed magnetic field on the dynamics of the orthopedic status, strength endurance of the trunk muscles, cardio-respiratory parameters and microcirculation in children with scoliosis of the II degree. The effectiveness, necessity and expediency of including high-intensity pulsed magnetic therapy in the program of medical rehabilitation of children with II degree scoliosis has been proved. The methodological recommendations are addressed to traumatologists — orthopedists, physiotherapists, physical therapy doctors, physical and rehabilitation medicine doctors, reflexologists, pediatricians, and other specialists of medical organizations.

Effect of high intensity pulsed magnetic field (30 T) on microstructure and tribological properties of Ni-based coatings

Pulsed magnetic fields can improve ferromagnetic and paramagnetic materials by improving their stress structure, domain variation, phase structure distribution and grain size of both solid and molten metals. Therefore, we strengthened the Ni-based wear-resistant coating by using the high-intensity (30 T) pulsed magnetic field equipment independently developed by our research group. The results show that the magnetic domains appeared as sheet domains and showed sinusoidal distribution after pulsed magnetic field intensification. The crystal structure is improved, the residual compressive stress is increased and the tribological coefficient is decreased. This study provides a new perspective on the design of high-strength metal base coatings for various applications.

STIRRING OF METAL MELTS FOR IMPROVING THE EFFICIENCY OF THE “LADLE – FURNACE” UNITS Message 2. NEW METHOD FOR ELECTROMAGNETIC STIRRING OF METALLIC MELT IN “LADLE – FURNACE” UNIT

The features of refractory lining’s wear of “ladle – furnace” unit at work on metallurgical mini-plant with intensive stirring of liquid metal by gas and electromagnetic field is studied. It was established that the most affected areas are slag zone, ladle’s bottom, as well as side wall, near which the electromagnetic stirrer is located. The stability of these areas determines the duration of the ladle working between repairs. Recommendations for recovery of the lining’s working layer have been developed. Also, there are formulated the requirements for rationalization of melt stirring modes. Theoretical studying of influence of electromagnetic stirring on heat & mass transfer processes in liquid metal bath of metallurgical aggregates (in particular, during homogenization of alloy in free turbulence mode at input of additives) was investigated. New electromagnetic stirrer was designed in the PTIMA NASU, and it is proposed for technologies of melting and finishing of alloys. The stirrer creates the pulsating magnetic field, and its force lines spread equally intensively both in the horizontal and vertical planes. It is shown that design of developed stirrer, its power supply by industrial frequency 50 Hz, and physical nature of the generated field’s action provide the simplicity of its making and operation. So, new stirrer has essential technical, economic and technological advantages in comparison with known stirrers of travelling magnetic field at the same parameters of electromagnetic systems. Joint research performed by specialists of the PTIMA NASU and IED NASU with using mathematical modeling and experiments on aluminum melt showed the following. It is possible to realize a wide range of stirring modes, both intensity and melt movement directions. Thus, the application of developed electromagnetic stirrer in the “ladle – furnace” units will allow to significantly expand the possibilities for finishing liquid alloys on chemical composition and temperature, especially at small metallurgical plants.

Pulsed field magnetization of a rectangular Y–Ba–Cu–O bulk, single grain superconductor assembly

The practical magnetization of arrays of multiple single grain, bulk high temperature superconductors is essential for practical applications, such as trapped flux rotating machines, magnetic resonance imaging and nuclear magnetic resonance. We report a systematic investigation of the pulsed field magnetization (PFM) of a bulk assembly consisting of two rectangular Y–Ba–Cu–O bulk single grains, in close proximity, at various temperatures. The measurements of the dynamic variation of the magnetic flux density, supported by numerical analysis, reveal that the induced screening currents during the rise of a pulsed field may greatly enhance the flux density in the region of the junction leading to uneven flux penetration and to an increased likelihood of flux jumps in this region. Such coupling between field and current promotes magnetic flux penetration and improves the peak trapped field from 3.01 T for a bulk single grain to 3.11 T for the bulk assembly at 30 K, improving the magnetization efficiency from 80% to 90%. The peak trapped field was further enhanced to 3.39 T and 3.31 T for the single bulk single grain and the bulk assembly, respectively, by employing a two-step multi-pulse PFM process.

Automation of Kerr microscopy system for domain wall velocity measurements

The present work reports the automation of a Kerr microscopy system for capturing magnetic domains and subsequently measuring the displacement of domain walls (DWs) with pulsed magnetic fields. Suitable algorithms are utilized for enhancing the image contrast, image filtering and the simultaneous quantitative evaluation of images, while the data acquisition with pulsed fields is run in the front-end. In order to test these aspects, DW velocity measurements in the widely studied Pt/Co/Pt system, which exhibits perpendicular magnetic anisotropy, are carried out at different temperatures (300 K). It is observed that the obtained features agree with the results reported in the literature, indicating the validity of the developed automation.

Effects of PMMT on microstructure and macrosegregation of large-sized 6061 alloy billet

The pulsed magnetic field melt treatment (PMMT) was applied in the direct chill (DC) casting of 6061 alloy billets with a diameter of 430 mm. The results indicated that the billet solidification structure was refined and homogenised. The grain size was reduced by 20.4% in the billet centre. Meanwhile, the PMMT can reduce the addition of grain refiner. The negative macrosegregation in the billet centre was reduced significantly. This can be attributed to the melt structure being changed by the energy of the pulsed magnetic field, which leads to the temperature of the melt variation and increased nucleation rate. This study may offer a promising method for the high-quality large-sized 6061 alloy billets preparation with less grain refiner.

On the high-field characterization of magnetocaloric materials using pulsed magnetic fields

Magnetic refrigeration is a highly active field of research. The recent studies in materials and methods for hydrogen liquefaction and innovative techniques based on multicaloric materials have significantly expanded the scope of the field. For this reason, the proper characterization of materials is now more crucial than ever. This makes it necessary to determine the magnetocaloric and other physical properties under various stimuli such as magnetic fields and mechanical loads. In this work, we present an overview of the characterization techniques established at the Dresden High Magnetic Field Laboratory in recent years, which specializes in using pulsed magnetic fields. The short duration of magnetic-field pulses, lasting only some ten milliseconds, simplifies the process of ensuring adiabatic conditions for the determination of temperature changes, . The possibility to measure in the temperature range from 10 to 400 K allows us to study magnetocaloric materials for both room-temperature applications and gas liquefaction. With magnetic-field strengths of up to 50 T, almost every first-order material can be transformed completely. The high field-change rates allow us to observe dynamic effects of phase transitions driven by nucleation and growth as well. We discuss the experimental challenges and advantages of the investigation method using pulsed magnetic fields. We summarize examples for some of the most important material classes including Gd, Laves phases, La–Fe–Si, Mn–Fe–P–Si, Heusler alloys and Fe–Rh. Further, we present the recent developments in simultaneous measurements of temperature change, strain, and magnetization, and introduce a technique to characterize multicaloric materials under applied magnetic field and uniaxial load. We conclude by demonstrating how the use of pulsed fields opens the door to new magnetic-refrigeration principles based on multicalorics and the ‘exploiting-hysteresis’ approach.

A bibliometric analysis of global publication trends on rTMS and aphasia.

Aphasia is one of the most devastating cognitive disorders caused by brain injury and seriously hinders patients' rehabilitation and quality of life. Repetitive transcranial magnetic stimulation involves the repeated application of extracranial pulsed magnetic fields to the local central nervous system to alter the membrane potential of cortical nerve cells, generating induced currents that affect brain metabolism and electrical activity. As one of the most popular noninvasive brain stimulation techniques, it has been used to treat aphasia. However, only a few bibliometric studies have examined the research direction and main findings in the field. To obtain an in-depth understanding of the research status and trend in this area, a bibliometric analysis based on the Web of Science database was conducted. VOSviewer (Leiden University, Leiden, Netherlands) and Microsoft Excel (Microsoft, Redmond, USA) were used to extract bibliometric information. Analysis of global distribution was conducted using the webpage mapping implement GunnMap2 (http://lert.co.nz/map/). Publications in this field were retrieved from the Web of Science Core Collection database, and 189 articles met the final inclusion criteria. The most influential authors, institutions, journals, and countries were Ralph MA from the University of Manchester, Harvard University, Neuropsychologia, and the USA, respectively. This study revealed publication patterns and emerging trends in the literature, providing a detailed and objective overview of the current state of research on repetitive transcranial magnetic stimulation for the treatment of aphasia. This information will be of great benefit to anyone seeking information about this field and can serve as a reference guide for researchers aiming to conduct further research.

Magnetic field induced reentrant multipolar ordering in the distorted kagome-lattice antiferromagnet Dy3Ru4Al12

We report on ultrasonic and magnetocaloric-effect measurements of the hexagonal antiferromagnet ${\mathrm{Dy}}_{3}{\mathrm{Ru}}_{4}{\mathrm{Al}}_{12}$ having a distorted kagome lattice. We observed a pronounced softening of the transverse modulus, ${C}_{44}$, above 30 T applied along [100], indicating an as-yet-unidentified magnetic field induced phase transition. We determined the field-temperature phase diagrams using pulsed magnetic fields up to 55.2 T, applied along [100] and [001]. Optimizing crystal-electric-field parameters within the mean-field approximation, we conclude that the enhancement of the field induced phase-transition temperature is due to electric quadrupolar and magnetic octupolar mediated interactions. We propose that the order parameter of the magnetic field induced phase transitions is the electric quadrupole ${O}_{zx}$, facilitated by octupole-mediated interactions.

Исследование внутреннего трения натуральной и модифицированной прессованием древесины березы повислой (Betula pendula Roth)

A method is proposed for approximating of the internal friction of wood based on the Boltzmann superposition principle, which describes the complex viscoelastic behavior of the system by a linear combination of components. Prepared samples of natural and modified wood, sawn from the stem part of drooping birch (Betula pendula ROTH) trees growing in the Khlevensky Forestry (52.184130, 39.110463, ASL 157m), were exposed to radial and tangential directions with ultrasound (frequency 24.5 kHz, exposure 0 -20 minutes, step 5 minutes) and pulsed magnetic field (strength - 0.3 T, exposure 0-2 minutes, step 0.5 minutes). Next, the internal friction of the samples was studied on an experimental setup using the logarithmic damping decrement based on free-bending vibrations. The absolute values of the dimensionless viscosity coefficient κ included in the model as the main structural parameter for samples of natural and modified wood were obtained at a significance level of p=0.95: for moisture content from 4.3 to 15; for ultrasound 4.6 to 20; for a pulsed magnetic field from 3.6 to 7.7. The absolute values of the dimensionless scaling factors μ for natural and modified wood samples range from 1.92 to 3.91. The highest approximation value was achieved when testing natural wood samples of silver birch (Betula pendula ROTH): R2=0.98 for the radial direction, the influence of the humidity factor, and R2=0.85 for the tangential direction, the influence of the ultrasonic factor, as well as for a sample of modified wood brand "Destam" in the radial direction R2=0.96, the influence of the factor of the pulsed magnetic field.

Algorithms of hysteresis interference

The calculated distribution of the electric voltage U at the output of the magnetic head (MG) scanning the magnetic carrier (MN) along the x coordinate is presented. The coordinates and amplitudes of the first maxima of hysteresis interference (HI) obtained in a pulsed magnetic field were found. Calculations with repeated use of the initial branch of the residual magnetization of the MN when constructing hysteresis interference are proposed. An analysis of the initial and hysteresis branches of signals for MH and other information carriers, signal converters and control systems has been carried out. The use of the obtained results allows to improve the quality of control of the properties of materials and objects.

O-vacancies induced in co-doped ZnO:(Cu,Fe) synthesized via hydrothermal method by pulsed magnetic field

Parent ZnO nanoparticles dually doped (Cu, Fe) were synthesized by the hydrothermal method in the presence of variant pulse magnetic field (PMF) at (0, 4T). X-Ray diffraction (XRD) was used to find crystal structure, Scanning Electron Microscope (SEM) revealed that the transformation of elongated spheres into spheres with increasing magnetic pulse (4T), Raman scattering peaks appeared at 437.70 and 436.63 cm−1 belonged to ZFCO-0T and ZFCO-4T indicated defects and inclusion of dopant elements in parent sample, XPS analysis showed that the decline in compressive strain enhances the contents of vacancies of oxygen (VO) for ZFCO-4T sample, and Bound Magnetic Polarons (BMPs) explained the RTFM order i.e.the sample ZFCO-4T has a higher number of polarons and they overlap excellently.

Realisation of the reconfigurable pulsed high magnetic field facility and its scientific application at Wuhan National Pulsed High Magnetic Field Centre

AbstractTo generate arbitrary shape magnetic field waveforms for advanced scientific research, a reconfigurable pulsed high magnetic field facility (PHMFF) was developed at Wuhan National Pulsed High Magnetic Field Centre (WHMFC). First, the basic elements of PHMFF are introduced, and a ternary physical model composed of energy storage unit, magnet, transmission circuits and other auxiliary units is summarised to describe various magnetic field systems. Second, in order to realise the reconfiguration of magnetic field systems based on detailed elements, the control system with the ability of dynamic construction and control sequence reconfiguration is designed. On this basis, the PHMFF has been realised and various magnetic field systems are constructed to produce arbitrary shape magnetic field waveforms, such as half‐sine, ultra‐high, flat‐top and repetitive field pulses, which not only enhances the capability and efficiency of PHMFF, but also makes more scientific research possible in pulsed magnetic fields. So far, a peak magnetic field of 94.8 T, a flat‐top magnetic field of 64 T/10 ms and a repetitive magnetic field waveform of 20 T/60 Hz have been achieved, and some experiments and studies on the physical properties of materials have been carried out at WHMFC.