New methods for processing and interpreting marine magnetic anomalies:Application to structure,oil and gas exploration,Kuril forearc,Barents and Caspian seas

New methods are presented for processing and interpretation of shallow marine differential magnetic data, including constructing maps of offshore total magnetic anomalies with an extremely high reso- lution of up to 1-2 nT, mapping weak anomalies of 5-10 nT caused by mineralization effects at the contacts of hydrocarbons with host rocks, estimating depths to upper and lower boundaries of anom- alous magnetic sources, and estimating thickness of magnetic layers and boundaries of tectonic blocks. Horizontal dimensions of tectonic blocks in the so-called ＂seismic gap＂ region in the central Kuril Arc vary from 10 to 100 km, with typical dimensions of 25-30 km. The area of the ＂seismic gap＂ is a zone of intense tectonic activity and recent volcanism. Deep sources causing magnetic anomalies in the area are similar to the ＂magnetic belt＂ near Hokkaido. In the southern and central parts of Barents Sea, tectonic blocks with widths of 30-100 kin, and upper and lower boundaries of magnetic layers ranging from depths of 10 to 5 km and 18 to 30 km are calculated. Models of the magnetic layer underlying the Mezen Basin in an inland part of the White Sea-Barents Sea paleorift indicate depths to the lower boundary of the layer of 12-30 km. Weak local magnetic anomalies of 2-5 nT in the northern and central Caspian Sea were identified using the new methods, and drilling confirms that the anomalies are related to concentrations of hydrocarbon. Two layers causing magnetic anomalies are identified in the northern Caspian Sea from magnetic anomaly spectra. The upper layer lies immediately beneath the sea bottom and the lower layer occurs at depths between 30-40 m and 150-200 m.

Magnetization plateaus and frequency dispersion of hysteresis on frustrated dipolar array

Competings or frustrated interactions are common for condensed matter systems. In consideration of the effect of dipole–dipole interaction, the static properties of square lattice spin systems are investigated using the Wang–Landau algorithm. The dynamic hysteresis is also simulated using the Monte Carlo(MC) method. The step-like magnetization under a DC magnetic field and two distinct peaks in hysteresis dispersion under an AC magnetic field are observed. Then, the formation of the properties of the frustrated dipolar array are discussed.

Investigation of magnetization reversal process in pinned CoFeB thin film by in-situ Lorentz TEM

Exchange bias effect has been widely employed for various magnetic devices.The experimentally reported magnitude of exchange bias field is often smaller than that predicted theoretically,which is considered to be due to the partly pinned spins of ferromagnetic layer by antiferromagnetic layer.However,mapping the distribution of pinned spins is challenging.In this work,we directly image the reverse domain nucleation and domain wall movement process in the exchange biased Co Fe B/Ir Mn bilayers by Lorentz transmission electron microscopy.From the in-situ experiments,we obtain the distribution mapping of the pinning strength,showing that only 1/6 of the ferromagnetic layer at the interface is strongly pinned by the antiferromagnetic layer.Our results prove the existence of an inhomogeneous pinning effect in exchange bias systems.

Study of magnetization reversal and anisotropy of single crystalline ultrathin Fe/MgO (001) film by magneto-optic Kerr effect

The magnetization reversal process of Fe/MgO （001） thin film is investigated by combining transverse and longi- tudinal hysteresis loops. Owing to the competition between domain wall pinning energy and weak uniaxial magnetic anisotropy, the typical magnetization reversal process of Fe ultrathin film can take place via either an ＂l-jump＂ process near the easy axis, or a ＂2-jump＂ process near the hard axis, depending on the applied field orientation. Besides, the hysteresis loop presents strong asymmetry resulting from the variation of the detected light intensity due to the quadratic magneto-optic effect. Furthermore, we modify the detectable light intensity formula and simulate the hysteresis loops of the Kerr signal. The results show that they are in good agreement with the experimental data.

Magnetization Reversal Process of Single Crystal a-Fe Containing a Nonmagnetic Particle

The magnetization reversal process and hysteresis loops in a single crystal α-iron with nonmagnetic particles are simulated in this work based on the Landau-Lifshitz-Gilbert equation. The evolutions of the magnetic domain morphology are studied, and our analyses show that the magnetization reversal process is affected by the interaction between the moving domain wall and the existing nonmagnetic particles. This interaction strongly depends on the size of the particles, and it is found that particles with a particular size contribute the most to magnetic hardening.

Demagnetization Process and Coercivity for Anisotropic HDDR NdFeB Bonded Magnets

The demagnetization process and the coercivity mechanism for amsotropic HDDR Nd(Fe,Co)B bonded magnets were studied by comparing the dependence of coercivity on the alignment field applied while the powders were pressed. The results showed that both the remanence and the coercivity of magnet increased with increasing alignment field. The demagnetization process of the magnet can be classified as the nucleation process inside the grains and the domain-wall motion between the grains. The combined effect of two processes determines the coercivity of HDDR NdFeB bonded magnets.

High Energy and High Coercivity Sintered NdFeB Magnets by Low Oxygen Process

Using ball milling and single direction pressing, we can produce high performance NdFeB sintered magnets. The oxygen content of sintered magnets can be controlled under 1500xl0^-6 and the magnetic performance can be improved by using low oxygen processing. The high preformance NdFeB sintered magnets with Br=(1.4 ± 0.2)T, iHc>796 kA/m and (BH)max=(390± 16) kJ/m^3, have been batch produced.

Cost-effective integrated strategy for the fabrication of hard-magnet barium hexaferrite powders from low-grade barite ore

Ultrafine barium hexaferrite（BaFe12O19） powders were synthesized from the metallurgical extracts of low-grade Egyptian barite ore via a co-precipitation route. Hydrometallurgical treatment of barite ore was systematically studied to achieve the maximum dissolution efficiency of Fe（～99.7%） under the optimum conditions. The hexaferrite precursors were obtained by the co-precipitation of BaS produced by the reduction of barite ore with carbon at 1273 K and then dissolved in diluted HCl and FeCl3 solution at pH 10 using NaOH as a base; the product was then annealed at 1273 K in an open atmosphere. The effect of Fe^3＋/Ba^2＋ molar ratio and the addition of hydrogen peroxide（H2O2） on the phase structure, crystallite size, morphology, and magnetic properties were investigated by X-ray diffraction, scanning electron microscopy, and vibrating sample magnetometry. Single-phase BaFe（12）O（19） powder was obtained at an Fe^3＋/Ba^2＋ molar ratio of 8.00. The formed powders exhibited a hexagonal platelet-like structure. Good maximum magnetization（48.3 A×m^2×kg^–1） was achieved in the material prepared at an Fe^3＋/Ba^2＋ molar ratio of 8.0 in the presence of 5% H2O2 as an oxidizer and at 1273 K because of the formation of a uniform, hexagonal-shaped structure.

Can we determine the filament chirality by the filament footpoint location or the barb-bearing？

We attempt to propose a method for automatically detecting the solar filament chirality and barb beating. We first introduce the concept of an unweighted undirected graph and adopt the Dijkstra shortest path algorithm to recognize the filament spine. Then, we use the polarity inversion line （PIL） shift method for measuring the polarities on both sides of the filament, and employ the connected components labeling method to identify the barbs and calculate the angle between each barb and the spine to determine the bearing of the barbs, i.e., left or right. We test the automatic detection method with Ha filtergrams from the Big Bear Solar Observatory （BBSO） Ha archive and magnetograms observed with the Helioseismic and Magnetic Imager （HMI） on board the Solar Dynamics Observatory （SDO）. Four filaments are automatically detected and illustrated to show the results. The barbs in different parts of a filament may have opposite bearings. The filaments in the southern hemisphere （northern hemisphere） mainly have left-bearing （fight- bearing） barbs and positive （negative） magnetic helicity, respectively. The tested results demonstrate that our method is efficient and effective in detecting the bearing of filament barbs. It is demonstrated that the conventionally believed one-to-one correspondence between filament chirality and barb bearing is not valid. The correct detection of the filament axis chirality should be done by combining both imaging morphology and magnetic field observations.

Magnetic properties and magnetization mechanism of anisotropic NdFeB/SmFeN hybrid bonded magnets prepared with different coercivity NdFeB powders

Anisotropic NdFeB/SmFeN hybrid bonded magnets were prepared by warm compaction process under an orientation magnetic field of 22 kOe,mixing with anisotropic SmFeN powders in different addition and HDDR-NdFeB powders in different coercivity.With the addition of 20 wt% SmFeN,the density and remanence of hybrid magnets increase from 5.58 g/cm~3,8.4 kGs to 6.02 g/cm~3,9.0 kGs,respectively.And as the addition amount of SmFeN powders varies from 20 wt% to 40 wt%,the maximum energy product changes less than 0.5 MGOe.In addition,the magnetization process and the interactions between two powders were studied.It is found that the magnetization process of anisotropic NdFeB powders shows distinction in different initial states.The addition of SmFeN powders promotes the rotation of NdFeB powders together with applied field,which is beneficial to the degree of alignment of NdFeB powders.Because of the micron-sized long range coupling effect,the coercivity of hybrid magnets decreases slowly with the increase of low coercivity SmFeN.Meanwhile,the magnetization process of hybrid magnets is different from pure magnets,it increases rapidly at low field and then slowly,next leads to rapidity again and achieves the saturation magnetization finally.

Temperature dependence of multi-jump magnetic switching process in epitaxial Fe/MgO(001) films

Temperature dependence of magnetic switching processes with multiple jumps in Fe/MgO（001） films is investigated by magnetoresistance measurements. When the temperature decreases from 300K to 80K, the measured three-jump hysteresis loops turn into two-jump loops. The temperature dependence of the fourfold in-plane magnetic anisotropy constant K1, domain wall pinning energy, and an additional uniaxial magnetic anisotropy constant KUare responsible for this transformation. The strengths of K1 and domain wall pinning energy increase with decreasing temperature, but KU remains unchanged. Moreover, magnetization reversal mechanisms, with either two successive or two separate 90°domain wall propagation, are introduced to explain the multi-jump magnetic switching process in epitaxial Fe/MgO（001） films at different temperatures.

Magnetic properties of misch-metal partially substituted Nd–Fe–B magnets sintered by dual alloy method

The misch-metal （MM） partially substituted Nd-Fe-B sintered magnets were fabricated by the dual alloy method, and the crystal structure, microstructure, and magnetic properties were analyzed comprehensively. X-ray diffraction （XRD） reveals that the increasing content of the MM has an inconsiderable effect on the crystallographic alignment of the magnets. Grains of the two main phases are uniformly distributed, and slightly deteriorate on the grain boundary. Due to the diffusion between the adjacent grains, the MM substituted Nd-Fe-B magnets contain three types of components with different Ce/La concentrations. Moreover, the first-order reversal curve （FORC） diagram is introduced to analyze the magnetization reversal process, coercivity mechanism, and distribution of reversal field in magnetic samples. The analysis indicates that there are two major reversal components, corresponding to the two different main phases. The domain nucleation and growth are determined to be the leading mechanism in controlling the magnetization reversal processes of the magnets sintered by the dual alloy method.

Research on Effect of Magnetized Pulp on Coal Slime Flotation

Effect of magnetization on oxygen concentration, pH, surface zeta potential, and wet heat of flotation pulp were researched. The result shows that magnetization treatment can improve the floatablility of coal and increase the difference in wet heat among coal, refuse, and pyrite, which is favorable for slime flotation and for removing sulfur and ash from coal.

Formation Process of Magnetized Fusion Target on the YingGuang 1 Device

Magnetized target fusion is an alternative method to fulfill the goal of controlled fusion, which combines advan- tages of both magnetic confinement fusion and inertial confinement fusion since its parameter space lies between the two traditional ways. Field reversed configuration （FFtC） is a good candidate of magnetized targets due to its translatable, compressible, high /3 and high energy density properties. Dynamic formation process of high density FFtC is observed on the YingGuang 1 device for the first time in China. The evolution of a magnetic field is detected with magnetic probes, and the compression process can be clearly seen from images taken with a high-speed multi-frame CCD camera. The process is also studied with two-dimensional magneto hydrodynamic code MPF-2D theoretically, and the results agree well with the experiment. Combining the experimental data and the theoretical analysis, the length of the formed FRC is about 39 cm, the diameter is about 2-2. 7cm, the average density is 1.3× 1016 cm-3, and the average temperature is 137eV.

Observational Features of Large-Scale Structures as Revealed by the Catastrophe Model of Solar Eruptions

Large-scale magnetic structures are the main carrier of major eruptions in the solar atmosphere. These structures are rooted in the photosphere and are driven by the unceasing motion of the photospheric material through a series of equilibrium configurations. The motion brings energy into the coronal magnetic field until the system ceases to be in equilibrium. The catastrophe theory for solar eruptions indicates that loss of mechanical equilibrium constitutes the main trigger mechanism of major eruptions, usually shown up as solar flares, eruptive prominences, and coronal mass ejections （CMEs）. Magnetic reconnection which takes place at the very beginning of the eruption as a result of plasma instabilities/turbulence inside the current sheet, converts magnetic energy into heating and kinetic energy that are responsible for solar flares, and for accelerating both plasma ejecta （flows and CMEs） and energetic particles. Various manifestations are thus related to one another, and the physics behind these relationships is catastrophe and magnetic reconnection. This work reports on recent progress in both theoretical research and observations on eruptive phenomena showing the above manifestations. We start by displaying the properties of large-scale structures in the corona and the related magnetic fields prior to an eruption, and show various morphological features of the disrupting magnetic fields. Then, in the framework of the catastrophe theory, we look into the physics behind those features investigated in a succession of previous works, and discuss the approaches they used.

Neural Mechanism in Emotion Regulation by Simultaneous Recording of EEG and fMRI

The combination of electroencephalogram (EEG) and functional magnetic resonance imaging(fMRI) is a very attractive aim in neuroscience in order to achieve both high temporal and spatial resolution for the non-invasive study of cognitive brain function. In this paper, we record simultaneous EEG-fMRI of the same subject in emotional processing experiment in order to explore the characteristics of different emotional picture processing, and try to find the difference of the subjects' brain hemisphere while viewing different valence emotional pictures. The late positive potential(LPP) is a reliable electrophysiological index of emotional perception in humans. According to the analysis results, the slow-wave LPP and visual cortical blood oxygen level-dependent (BOLD) signals are both modulated by the rated intensity of picture arousal. The amplitude of the LPP correlate significantly with BOLD intensity in visual cortex, amygdala, temporal area, prefrontal and central areas across picture contents.

Magnetic relaxation behavior of a spatially closed dysprosium(Ⅲ) phthalocyaninato double-decker complex

The SMM properties of the spatially closed Dy（Ⅲ） double-decker Pc complex Dy（obPc）2 （1）, which is equivalent to a pseudo dinuclear complex, are reported. Complex 1 crystallized with ethanol in the crystal lattice in the monoclinic space group P22/n and was isomorphous with Tb（obPc）2 （3）, which is arranged in a dimer structure along the b axis. The intermetallic Dy-Dy distance was determined to be 0.756 nm. ZMT versus T plots for 1 decreased with a decrease in T, which suggests the existence of an antiferromagnetic （AF） interaction between the Dy3＋ ions. The M-H curve for 1 at 1.8 K showed magnetic hysteresis. In ac susceptibility measurements on a powder sample of 1, which were dependent on the applied ac field, indicating that 1 is an single molecule magnet （SMM）, a maximum appeared at 22 K at an ac frequency 09 of 1488 Hz. The shape of the peaks dras- tically changed, and the peaks did not shift when an Hd~ large enough to suppress the quantum tunneling of the magnetization （QTM） was applied. The energy barrier （A/hc） was estimated to be 44 cm-1 with a pre-exponential factor （r0） of 1.6 × 10-5 s from an Arrhenius plot. Our results suggest that the SMM/magnetic properties of 1 significantly change in a dc magnetic field. These relaxation mechanisms are related to the energy gap of the ground state and to QTM.

Dy gradient and coercivity in grain boundary diffusion processed Nd-Fe-B magnet

By controlling Dy vapor deposition process, the amount of Dy that diffused into the magnet was increased gradually from 0.1 wt.% to 0.3 wt.%. Compared with the original status, the coercivity increment was not proportional to the Dy diffusion amount. Subsequent H（cj） and Dy content gradient data showed that slope of the 0.3 wt.% sample gradient was bigger than that of 0.1 wt.% one, and the gaps between outer flakes and inner flakes enlarged with the increasement of Dy diffusion amount. Although Dy mostly enriched in triple-junction regions in electron-probe microscope analysis（EPMA） images, the following Auger depth graph showed that Dy content was as high as 3.0 at.% in 1.5 mm deep center. It proved that Dy tended to get into the main phase rather than stayed in the grain boundary during the diffusion process, and over-diffusion of Dy in the main phase was unhelpful for the coercivity enhancement.

Anisotropic NdFeB/SmCoCuFeZr composite bonded magnet prepared by warm compaction process

Anisotropic NdFeB/SmCoCuFeZr composite bonded magnets were prepared by warm compaction process. The effects of adding SmCoCuFeZr magnetic powder on the properties of anisotropic bonded NdFeB magnet were investigated in this work. The results show that, both magnetic properties and temperature stability of the bonded magnet can be improved by adding fine SmCoCuFeZr magnetic powder. In the present study, the optimal content of SmCoCuFeZr magnetic powder was about 20 wt.%, in this case, the Br, Hcj, and（BH）maxof the NdFeB/SmCoCuFeZr composite magnet achieved 0.943 T, 1250 kA/m, and168 kJ/m^3, respectively.

Observation of magnetic domain evolution in constrained epitaxial Ni–Mn–Ga thin films on MgO(0 0 1) substrate

Epitaxial Ni–Mn–Ga thin films have promising application potential in micro-electro-mechanical sensing and actuation systems. To date, large abrupt magnetization changes have been observed in some epitaxial Ni–Mn–Ga thin films, but their origin-either from magnetically induced martensite variant reorientation(MIR) or magnetic domain evolution-has been discussed controversially. In the present work, we investigated the evolutions of the magnetic domain and microstructure of a typical epitaxial Ni–Mn–Ga thin film through wide-field magneto-optical Kerr-microscopy. It is demonstrated that the abrupt magnetization changes in the hysteresis loops should be attributed to the magnetic domain evolution instead of the MIR.