Magnetic Patterns Research Articles

Single heading-line survey of MGTS for magnetic target pattern recognition

Single heading-line survey of MGTS for magnetic target pattern recognition

Temperature-dependent Scaling Behavior of Magnetic Hysteresis Loop of CoFeB/Pd Multilayer Film

We report our experimental investigation on the temperature-dependent hysteresis loops and magnetic domain behaviors of CoFeB (0.4 nm)/Pd (1 nm) multilayer on polyimide substrate with a perpendicular magnetic anisotropy, by means of magneto-optical Kerr microscopy. Hysteresis characteristics such as saturation magnetization, coercivity, and hysteresis loop area with respect to the temperature have been analyzed, where powerlaw scaling behaviors are observed with microscopic magnetic domain patterns mediated by numerous nucleation sites.

Brain imaging findings in CLCN2-related leukoencephalopathy.

CLCN2-related leukoencephalopathy is a rare autosomal-recessive disease caused by a loss-of-function mutation in the ClC-2 chloride channel, which is fundamental in ion and water brain homeostasis. With only 31 cases published in the literature, its precise pathophysiology is uncertain, clinical manifestations are nonspecific and little is known in terms of prognosis. Neuroimaging plays a fundamental role in the identification of CLCN2-related leukoencephalopathy, which has a typical magnetic resonance imaging pattern that, when recognized, should promote proper genetic study for diagnostic confirmation. We report a paediatric clinical case of CLCN2-related leukoencephalopathy with genetically verified c.1709G > A p(Trp570*) mutation, highlighting typical neuroimaging findings and the importance of imaging in the diagnostic approach.

Symmetry-dependent ultrafast manipulation of nanoscale magnetic domains

Femtosecond optical pumping of magnetic materials has been used to achieve ultrafast switching and recently to nucleate symmetry-broken magnetic states. However, when the magnetic order parameter already presents a broken-symmetry state, such as a domain pattern, the dynamics are poorly understood and consensus remains elusive. Here, we resolve the controversies in the literature by studying the ultrafast response of magnetic domain patterns with varying degrees of translation symmetry with ultrafast x-ray resonant scattering. A data analysis technique is introduced to disentangle the isotropic and anisotropic components of the x-ray scattering. We find that the scattered intensity exhibits a radial shift restricted to the isotropic component, indicating that the far-from-equilibrium magnetization dynamics are intrinsically related to the spatial features of the domain pattern. Our results suggest alternative pathways for the spatiotemporal manipulation of magnetism via far-from-equilibrium dynamics and by carefully tuning the ground-state magnetic textures.6 MoreReceived 8 July 2022Revised 25 November 2022Accepted 29 November 2022DOI:https://doi.org/10.1103/PhysRevB.106.224424©2022 American Physical SocietyPhysics Subject Headings (PhySH)Research AreasMagnetic domainsMagnetismUltrafast demagnetizationUltrafast magnetization dynamicsTechniquesCoherent X-ray scatteringUltrafast femtosecond pump probeAccelerators & BeamsNonlinear DynamicsCondensed Matter, Materials & Applied Physics

Magnetic patterning of Co/Ni layered systems by plasma oxidation

We studied the structural, chemical, and magnetic properties of Ti/Au/Co/Ni layered systems subjected to plasma oxidation. The process results in the formation of NiO at the expense of metallic Ni, as clearly evidenced by X-ray photoelectron spectroscopy, while not affecting the surface roughness and grain size of the Co/Ni bilayers. Since the decrease of the thickness of the Ni layer and the formation of NiO increase the perpendicular magnetic anisotropy, oxidation may be locally applied for magnetic patterning. Using this approach, we created 2D heterostructures characterized by different combinations of magnetic properties in areas modified by plasma oxidation and in the regions protected from oxidation. As plasma oxidation is an easy to use, low cost, and commonly utilized technique in industrial applications, it may constitute an improvement over other magnetic patterning methods.

Controlled Transport of Magnetic Particles and Cells Using C-Shaped Magnetic Thin Films in Microfluidic Chips.

Single-cell analysis is an emerging discipline that has shown a transformative impact in cell biology in the last decade. Progress in this field requires systems capable of accurately moving the cells and particles in a controlled manner. Here, we present a microfluidic platform equipped with C-shaped magnetic thin films to precisely transport magnetic particles in a tri-axial rotating magnetic field. This innovative system, compared to the other rivals, offers numerous advantages. The magnetic particles repel each other to prevent undesired cluster formation. Many particles move synced with the external rotating magnetic field, which results in highly parallel controlled particle transport. We show that the particle transport in this system is analogous to electron transport and Ohm's law in electrical circuits. The proposed magnetic transport pattern is carefully studied using both simulations and experiments for various parameters, including the magnetic field characteristics, particle size, and gap size in the design. We demonstrate the appropriate transport of both magnetic beads and magnetized living cells. We also show a pilot mRNA-capturing experiment with barcode-carrying magnetic beads. The introduced chip offers fundamental potential applications in the fields of single-cell biology and bioengineering.

Theoretical study of the magnetic properties of the CoCu2O3 compound

In this paper we present a theoretical study of the magnetic properties of the ${\mathrm{CoCu}}_{2}{\mathrm{O}}_{3}$ compound. The magnetic effective exchange interactions and zeroth-field splitting were computed using ab initio methods, then the magnetic order and transition temperature were determined using classical Monte Carlo simulations. We showed that, unlike other members of the $A{\mathrm{Cu}}_{2}{\mathrm{O}}_{3}$ family, the presence of an additional magnetic atom, associated with a large folding of the puckered layers in the ($\stackrel{P\vec}{a}, \stackrel{P\vec}{b}$) directions, induces a magnetic pattern based on coupled three-leg ladders, quite different from the two-leg structural ladders. The propagation vector has been found to be $\stackrel{P\vec}{q}=(0,\frac{1}{2},\frac{1}{2})$. It is associated with a doubly degenerated ground state suggesting a doubling of the unit cell. The large ${\mathrm{Co}}^{2+}$-ion anisotropy was shown to be of crucial importance in the high transition temperature observed in this compound.

Divergent magnetic resonance imaging atrophy patterns in Alzheimer’s disease and primary age‐related tauopathy

AbstractBackgroundPrimary age‐related tauopathy (PART) is a pathological disorder characterized by the presence of tau‐positive neurofibrillary tangles (NFTs) and no amyloid‐beta (Aβ) deposition (“definite PART”). Currently, the diagnosis of PART is histologically assessed by the presence of tau positive NFT with Braak staging and a Consortium to Establish a Registry for Alzheimer’s disease (CERAD) Aβ stage of 0.MethodOur study compared brain magnetic resonance imaging (MRI) with neuropathological findings in patients with PART and AD, while assessing the relationship between brain atrophy and clinical impairment. We analysed 233 participants: 32 with no plaques (“definite” PART ‐ CERAD 0), and 201 cases within the AD spectrum, with 25 with sparse (CERAD 1), 76 with moderate (CERAD 2) and 100 with severe (CERAD 3) degree of neuritic plaques.ResultUpon correcting for age, sex and age difference at MRI and death, there were significantly higher levels of atrophy in CERAD 3 compared to CERAD 1‐2 and a trend compared to CERAD 0. In the anterior temporal region, there was a trend for higher levels of atrophy in CERAD 0 compared to CERAD 1. We then assessed the correlation between regional brain atrophy and CDR‐sum‐of‐boxes score for PART and AD, and found that overall cognition deficits are directly correlated with regional atrophy in the AD continuum, but not in definite PART. We further observed correlation between regional brain atrophy with multiple neuropsychological metrics in AD, while PART showed only specific correlations between language deficits and anterior temporal atrophy.ConclusionOverall, these findings support PART as an independent pathologic process from AD.

A synthesis of fauna, palaeoenvironments and stratigraphy of the Miocene Tagay locality (Olkhon Island, Lake Baikal, Eastern Siberia)

We report about the Early Miocene Tagay fauna of Olkhon Island, the largest island of the Baikal Lake. The Tagay fauna is of high scientific importance because of the diversity of fishes, amphibians, lizards, snakes, turtles, manifold birds and mammals. The lithology, geochemistry and the fossil record along the Tagay-1 section allow reconstruction of various palaeoenvironments, i.e. open water, shallow lakes with adjacent wetlands, riverine woodlands, and also forested and dry habitats. The fossil record, lithology and geochemical sediment-analyses suggest a temperate palaeoclimate with short humid and dry periods. The small mammal record and the magnetic polarity pattern of the upper part of section Tagay-1 correlate with the subchrons C5Cn.2r – C5Cn.1r of Chron C5C and the late Burdigalian Stage of the Geologic Time Scale (GTS2000). The corresponding age range of the Tagay fauna is ~16.5 to ~16.3 Ma.

Magnetic Systems for Regenerative Medicine

Magnetic Systems for Regenerative Medicine

Palaeomagnetic data from the late Cenozoic Tagay section (Olkhon Island, Baikal region, Eastern Siberia)

One of the most important fossil fauna localities in the Baikal region is the Tagay section. It is located on the shore of Tagay bay at the northwestern coast of Olkhon Island in the Baikal Lake and consists of two different exposures, Tagay-1 and Tagay-2. The Tagay-1 section exposes predominantly lake sediments of Miocene age and contains a faunal complex. The Tagay-2 section is composed of slope wash and subaerial sediments of Early Pleistocene (Calabrian?) age with remains of small mammals. A total of 95 samples for palaeomagnetic studies were taken in both sections. Magnetic susceptibility (MS), its frequency dependence (Fd) and anisotropy were measured from all samples. The stable component of the natural remanent magnetization (NRM) was obtained using stepwise alternating field (AF) demagnetization. The magnetic polarity pattern was constrained for the Tagay-1 section. It includes an extended zone of reversed polarity, complicated by three normal subzones of minor rank. Palaeontological data allow correlation of the Tagay-1 pattern with the magnetic chrons C5Dn to C5Cn.1n (late Burdigalian – early Langhian). Palaeomagnetic directions in the upper part of the Tagay-2 section are randomly distributed due to intensive slope-wash processes resulted in mechanical perturbation of the sediments. The lower part of Tagay-2 section demonstrates only reversed polarity, although the scatter of directions is quite large due to landsliding. This reversed interval may be correlated with the Matuyama chron between Cobb Mountain and Olduvai subchrons. Synchronous increase of MS and Fd values in palaeosols suggests a pedogenic (or “Chinese”) mechanism influencing magnetic properties of the Tagay-2 section under warm palaeoclimatic conditions.

Images Reconstruction from Functional Magnetic Resonance Imaging Patterns Based on the Improved Deep Generative Multiview Model

Reconstructing visual stimulus images from the brain activity signals is an important research task in the field of brain decoding. Many methods of reconstructing visual stimulus images mainly focus on how to use deep learning to classify the brain activities measured by functional magnetic resonance imaging or identify visual stimulus images. Accurate reconstruction of visual stimulus images by using deep learning still remains challenging. This paper proposes an improved deep generative multiview model to further promote the accuracy of reconstructing visual stimulus images. Firstly, an encoder based on residual-in-residual dense blocks is designed to fit the deep and multiview visual features of human natural state, and extract the features of visual stimulus images. Secondly, the structure of original decoder is extended to a deeper network in the deep generative multiview model, which makes the features obtained by each deconvolution layer more distinguishable. Finally, we configure the parameters of the optimizer and compare the performance of various optimizers under different parameter values, and then the one with the best performance is chosen and adopted to the whole model. The performance evaluations conducted on two publicly available datasets demonstrate that the improved model has more accurate reconstruction effectiveness than the original deep generative multiview model.

Application of anisotropy of magnetic susceptibility to construct the palaeocurrent direction using slender fossil orientations

Oriented samples were collected in the southern Mongolia Plateau and north‐eastern Tibetan Plateau to detect links between microstructural features, which are inferred from magnetic fabrics, and outcrop‐scale sedimentary structures that include slender fossil orientations. Palaeocurrent imprints in particles and their recognition in magnetic fabrics depend on the kinetics of current and any post‐depositional reworking. Here, we restored the flooding palaeocurrent direction through the statistical orientation of slender fossils and imprints indicated by magnetic fabric patterns in the sediments. We found that the tilt response of the minimum susceptibility axes preserves more links to the dynamic orientation of fossil deposits, while the maximum susceptibility axes may be easily reworked by a weak but long‐term tectonic compression. Comparing the two methods reveals the correlation between fossil distribution and magnetic fabric. The dynamic identification of anisotropy of magnetic susceptibility on large quantitative samples contributes to provide an alternative way for further statistics of fine‐grained sediments and fabric arrangement.

Interface change of Pr-Fe-B thin films with different ferromagnetic compositions

The thin film structure of the Si3N4/Pr-Fe-B/Si3N4/glass substrate was fabricated by the sputtering process followed by an in-situ annealing process at 650 °C. The changes at the interface of magnetic layer/underlayer were investigated with simultaneous addition of Fe content in the range of 68.9 to 76.61 at.% during the sputtering process. With ferromagnetic properties and more reactive and movable capacity of Fe, the addition of Fe created significant changes in the crystal structure, surface morphology, microstructure, and magnetic properties in Pr-Fe-B thin films. X-ray diffraction results confirmed the presence of two Pr2Fe14B and Pr2Fe23B3 magnetic phases in the thin films. The surface morphology of the thin films observed through SEM pictures and AFM images showed the blossom phenomenon with various grain sizes and surface roughness, respectively. The microstructure of the thin films through HR-TEM pictures revealed the discernable change at the interface of the Pr-Fe-B layer/Si3N4 underlayer. The new Fe3Si underlayer formed different thicknesses at the interface corresponding to various Fe contents. The stacking of (100) and (010) planes of Pr2Fe14B phase with different d-spacings was observed at higher magnification of HR-TEM. Results of magnetic measurement showed that the thin film at 73.32 at.% Fe content had the better growth potential of perpendicular magnetic anisotropy (PMA) and obtained a higher coercivity of approximately 4.5 kOe. MFM images through magnetic domain observation showed that the thin films had the same magnetic domain pattern but varied in magnetic domain size. Analysis of saturation magnetization and effective uniaxial anisotropy of the thin films showed the contribution of the interface magnetic anisotropy (to the PMA with the value of Ki = 122.25 × 106 erg/m2.

Surface imprinting by using bi-functional monomers on spherical template magnetite for selective detection of levodopa in biological fluids

The present work introduces an innovative biosensing platform for greatly sensitive determination of levodopa medicine. Initially, spherical magnetic (SM) nanoparticles were prepared by hydrothermal fabrication approach and used as a pattern to make spherical magnetic molecular imprinted polymer (SMMIP). Afterward, levodopa-molecularly imprinted layer was grown on the surface of the spherical magnetic pattern by electropolymerization with dopamine and resorcinol as bi-functional monomers and levodopa as a template molecule, which enhanced the specific recognition of the sensing platform to levodopa. The presence of SM nanoparticles could not only accelerate the mass transfer, the electron transport rate, and improve specific surface area of the electrode but also facilitate the recognition of the polymer, in this way increasing the current response and improving the performance of the biosensor. The superior sensing efficiency of the presented biosensor was confirmed based on the low limit of detection of 10 nmol L−1 which represented two linear ranges from 0.5 to 200 μmol L−1 and 200–1000 μmol L−1 for levodopa. More importantly, the practicability of the biosensor was proved by detecting levodopa in tablet, blood serum and plasma, implying that the sensing platform was suitable for monitoring levodopa in actual biological fluid and medicine.

Megashears and hydrothermalism at the Martian crustal dichotomy in Valles Marineris

Observations of ancient deep deformation systems on Mars are important for constraining planetary dynamics, as well as to identify potential mineral resources. However, such systems were thought to be unexposed and inaccessible to analysis. Here, we apply structural and hyperspectral analyses, and correlate results with magnetic anomaly patterns, to investigate two large right-lateral brittle-ductile shear zones and fault megabreccia exposed in the deepest parts of Valles Marineris. The shear zones follow the trace of the edge of the Borealis impact basin, thought to represent the planetary dichotomy boundary. We identify hydrothermally altered mafic igneous rocks in the sheared basement. We suggest that the shear system was initiated as basin ring fault system in the pre-Noachian, with further reactivation up until the Hesperian, and may still be a potential source of marsquakes. Hydrothermal circulation through the shear zones may have initiated primary mineralizations which are promising for base and rare metal exploration.

Ground magnetic survey and 3D geophysical model of ultrabasic rocks from the Martín García Complex (Buenos Aires, Argentina)

The Martín García Complex, which crops out at the homonymous island of the Río de la Plata Estuary, is composed of intermediate to silicic orthogneisses and granitoids, hornblende and olivine gabbros, and felsic dykes of Paleoproterozoic and Mesoproterozoic ages, as well as serpentinized ultrabasic rocks of unknown age. A major part of this igneous-metamorphic basement is covered by sediments and vegetation, hiding the relationships between the different rock units, and hindering their study. Therefore, a ground magnetic survey and the consequent 3D geophysical modeling were conducted to elucidate the geometry of the ultrabasic bodies in the subsurface. Normal and reverse dipolar sub-circular and elongated (∼ENE-WSW) magnetic anomalies were identified. It is proposed that Cr-rich spinels would be responsible for some of the detected magnetic anomalies. Our results suggest the existence of three magnetic units with a dyke-type geometry, all of them with ∼ENE-WSW trend and steep dip. The magnetic survey and 3D modeling allowed us to confirm the continuity and extension in the subsurface of the ultrabasic bodies cropping out discontinuously on the surface. According to their crosscutting relationships, a post-Stenian age is proposed for these rocks. Magnetic patterns identified in Martín García Island are similar to those observed in western Uruguay, suggesting that the Martín García Complex would be part of the Piedra Alta Terrane (Río de la Plata Craton).

Temperature Rise Calculation of Magnetic Core Considering the Temperature Effect of Magnetic Properties in an Electrical Steel Sheet

The magnetic properties of electrical steel sheets are affected by magnetization patterns, working temperature, and external pressure. In order to study the temperature effect of electrical steel sheets on the temperature rise of a transformer core, in this paper, based on the magnetic property test system of an electrical steel sheet, the permeability and loss of a 50AW600 grain non-oriented electrical steel sheet and a 30ZH120 grain oriented electrical steel sheet under different temperatures and excited frequencies were measured, and the influence of temperature on the properties of the material was analyzed. A magneto-thermal iterative coupling method considering the temperature effects of magnetic properties in the electrical steel sheet was investigated. Based on the above measurement data and iterative coupling method, the temperature distribution of the core of a 500-kV power transformer was simulated and analyzed, and compared with the simulation results of the traditional coupling method without considering the temperature effect of the electrical steel sheet. Magneto-thermal coupling simulation under no-load operation is a symmetrical problem. It was found that the temperature of the hottest spot of the transformer core calculated by the magneto-thermal iteration method proposed in this paper was significantly reduced, the temperature of the hottest spot on the core column was about 45 °C, and the temperature of the hottest spot on the upper and lower yoke was about 39 °C, which provides an effective simulation method for accurately calculating the temperature rise distribution of electrical products such as transformers.

Manipulation of Magnetic Skyrmion Density in Continuous Ir/Co/Pt Multilayers

We show that magnetic skyrmions can be stabilised at room temperature in continuous [Ir/Co/Pt]5 multilayers on SiO2/Si substrates without the prior application of electric current or magnetic field. While decreasing the Co thickness, a transition of the magnetic domain patterns from worm-like state to separated stripes is observed. The skyrmions are clearly imaged in both states using magnetic force microscopy. The density of skyrmions can be significantly enhanced after applying the "in-plane field procedure". Our results provide means to manipulate magnetic skyrmion density, further allowing for the optimised engineering of skyrmion-based devices.

The Supersonic Flutter Behavior of Sandwich Plates with an Magnetorheological Elastomer Core and Gnp-Reinforced Face Sheets

This paper is provided to study the supersonic flutter behavior of sandwich plates with a magnetorheological (MR) core and polymeric face sheets reinforced with graphene nanoplatelets (GNPs). The mathematical modelings of the plate and the aerodynamic pressure of the fluid flow are performed utilizing the first-order shear deformation theory (FSDT) and the linear piston theory, respectively. The effective mechanical properties of the face sheets are estimated utilizing the rule of mixture along with the Halpin–Tsai model. Hamilton’s principle is employed to derive the governing equations and associated boundary conditions and these equations are solved using a semi-analytical approach for a Levy-type plate. The influences of different parameters on the aeroelastic stability of the plate are investigated such as the thickness of the MR core, magnetic field intensity, distribution pattern and mass fraction of the GNPs, boundary conditions, and geometrical parameters of the plate. This paper is the first theoretical attempt to study the effects of MR materials on the aeroelastic stability of Levy-type moderately thick sandwich plates and presents useful results that will be useful in the future of air vehicles.