Variable Magnetic Susceptibility Research Articles

Silurian to Early Triassic Magnetic Susceptibility Variations in the South Yellow Sea and Their Environmental Implications: Records From the CSDP‐2 Well

ABSTRACTUntil recently, no physical rock samples from the Palaeozoic to Mesozoic eras had been recovered from the South Yellow Sea (SYS), leaving the palaeoclimatic significance of this period largely unexplored. This study analyzes data from the Lower Silurian to Lower Triassic strata of the CSDP‐2 Well, including magnetic susceptibility (MS) data from 251 samples and geochemical element data for 345 samples, to determine environmental changes and their implications. We successfully establishes vertically continuous and complete MS and geochemical curves within the SYS, and two depth segments with anomalous values and four climatic shifts are identified. Through the coupled analysis of MS and geochemical data, along with the synthesis of previously published data, one anomalous segment from 1690‐2006. 9 meters below sea floor (mbsf) could represent the Late Devonian‐Early Permian Ice Age, which lasted approximately 80 Ma. Another segment from 820‐930 mbsf represents Emeishan and Siberian volcanism, with an interval between the two events spanning approximately 2.7 Ma. And 15 variation cycles are identified by analyzing changes of MS values, we found that geological event cycles spanned 3‐9 Ma during the Early Silurian to Permian, but the interval shorten to approximately 28.6 Kyr in the Early Triassic. In summary, the CSDP‐2 Well records several significant geological events and the SYS underwent an exceptionally complex evolution of geological environments during the Early Mesozoic. Additionally, MS data from CSDP‐2 Well reveal unique variation patterns not seen in adjacent areas or other blocks, indicating that while the SYS was influenced by global climate and tectonic activities at block‐level, it also experienced distinct regional geological environmental changes.

Operando monitoring the redox activity of sodium vanadium titanium phosphate electrodes in organic and aqueous electrolytes by magnetometry

The bulk oxidation states of the transition metals in Na2VTi(PO4)3 are monitored continuously based on magnetic susceptibility variations. It is shown that the same charge compensation processes occur in organic and aqueous electrolytes.

Assessing soil erosion risk through geospatial analysis and magnetic susceptibility: A study in the Oued Ghiss dam watershed, Central Rif, Morocco

In northern Morocco, water erosion presents a critical risk for soil degradation and dam sedimentation, attributable to extreme climatic conditions, variegated topography, lithological vulnerabilities, and anthropogenic pressures. This study quantitatively and spatially evaluates soil erosion susceptibility within the catchment area of the Oued Ghiss dam in Central Rif, Morocco. Utilizing the Revised Universal Soil Loss Equation (RUSLE) integrated with Geographic Information Systems (GIS) and calibrated through magnetic susceptibility metrics, the study provides a detailed analysis of erosion factors. The model was applied using GIS to spatially analyze data on rainfall, soil type, topography, land cover, and management practices, with magnetic susceptibility measurements used to calibrate the model by identifying stable and erosion-prone areas. The resultant soil loss map reveals a mean erosion rate of 24 t/ha/year. Specifically, 37.28 % of the catchment area exhibits an erosion rate under 5 t/ha/year, 40.16 % between 5 and 10 t/ha/year, 22.77 % between 10 and 20 t/ha/year, and 0.86 % surpasses 20 t/ha/year. Magnetic susceptibility measurements across various soil profiles indicated that stable soils showed increased susceptibility towards the surface, while eroded soils displayed decreased susceptibility, with significant correlations found between magnetic susceptibility variations and the final risk map. This innovative calibration of the RUSLE model through magnetic susceptibility improves erosion vulnerability assessments and results in a more detailed soil loss map. The findings provide critical information for policymakers to develop targeted management plans for erosion-prone areas, particularly benefiting the Ghiss dam watershed, where these insights will aid in preventing dam siltation and enhancing water resource management. This confirms magnetic susceptibility's reliability in assessing soil erosion vulnerability and improving numerical models.

Strongly Negative Low‐Field Variation of Magnetic Susceptibility: Rock Magnetic Character of the Basement‐Cover Interface of Northeastern Oklahoma

AbstractSome rock and soil samples exhibit significant loss of magnetic susceptibility (χ) with increasing applied field amplitude even at relatively low (10–100s of A/m) fields, a behavior which remains unexplained. Exceptionally strong negative field‐dependence of susceptibility (χHD) is present in sandstones and altered intermediate‐felsic igneous rocks in several cores from the northeastern Oklahoma subsurface. These same rocks also show elevated frequency‐dependence of susceptibility (χFD), with reasonable correlation of χHD to χFD, and frequency‐dependent χHD. Results from multiple characterization methods indicate that strongly negative χHD in these rocks is linked to a yet‐unidentified phase which begins the approach to magnetic saturation in low fields (<1 mT/800 A/m), shows elevated χFD to low temperatures, is unstable at high temperatures, possesses significant anisotropy of magnetic susceptibility, and becomes paramagnetic above ∼83°C. Clear associations with fluid alteration features indicate that this material may be highly relevant to rock alteration, diagenetic, and environmental studies.

The usefulness of the magnetic susceptibility of loess paleosol sequences for paleoclimate and stratigraphic studies: The case of the Quaternary Palouse loess, northwestern United States

Worldwide, Quaternary loess-paleosol sequences archive terrestrial paleoenvironmental information. The Palouse loess in the northwestern USA is one such deposit representing at least a million years of sediment accumulation. Loess paleosol sequences are often studied via the magnetic susceptibility of sediments and the changes in susceptibility with depth. However, since variations in magnetic susceptibility can have different underlying causes, the interpretation of the magnetic susceptibility of loess depends on factors specific to each major loess region. We measured the magnetic susceptibility of sediments along depth profiles in a well-studied exposure of the Palouse loess in eastern Washington, USA (the “CLY-2 site,” 46.3131° N, 118.4874° W, WGS84). Our measurements show that the magnetic susceptibility of sediments in the Palouse loess varies systematically and predictably with depth and can be correlated with other magnetic susceptibility profiles at the outcrop scale and at the regional scale. We also measured changes in grain size, elemental abundance, mineralogy, and other magnetic properties to determine the most likely cause of the magnetic susceptibility signal. Based on these results, variations in magnetic susceptibility in the Palouse are likely driven mostly by changes in coarse sediment supply and accumulation of tephra rather than changes in weathering. Magnetic susceptibility is useful as an inexpensive, non-destructive tool for stratigraphic correlation of Quaternary loess deposits in the Palouse, especially in combination with paleosol stratigraphic markers and known tephra deposits.

Holocene paleoenvironmental history of Jackson Lake (Grand Teton National Park, USA) deduced from CHIRP seismic reflection and radiocarbon-dated sediment cores

Sedimentary records from Jackson Lake (Grand Teton National Park, Wyoming, USA) provide an opportunity to investigate the Late Quaternary tectonic and hydroclimatic history of a region known to have considerable earthquake hazard potential. Here, we present a new paleoenvironmental reconstruction for Jackson Lake using high-resolution Compressed High-Intensity Radar Pulse (CHIRP) seismic reflection data and sediment cores from Moran Bay, which is adjacent to the active Teton fault on the southwestern lake margin. Three seismic units (SU) are present within Moran Bay. The lowermost SU-1 defines the acoustic basement, which is characterized by a sharp reflector of variable relief above material with a very low signal-to-noise seismic response; direct sampling reveals this unit to be glaciogenic in origin. SU-2 contains diverse acoustic facies that onlap, downlap, and drape underlying strata. Prominent in SU-2 are faulted, folded, and slumped reflections with mixed amplitude characteristics, as well as reflections organized into prograding clinoforms, which suggest a history of deformation and slope instability in fluvio-deltaic and shallow lacustrine environments. A local unconformity separates SU-2 and SU-3, and above this boundary clinoform packages backsteps towards the hinterland. A bi-directionally tapering package of low-moderate amplitude, continuous to semi-continuous reflections onlap the clinoform; this unit was fully cored (13.8 m), allowing the unit boundary to be sampled and dated. Radiocarbon ages indicate that the core spans ca. 10.4 calibrated kiloyears before present (cal ka BP) to present. Retrogradational stacking of deltaic clinoforms are best explained by increased accommodation in Moran Bay around ca. 10 ka, consistent with a major earthquake and hanging wall subsidence on the Teton fault. Two turbidites identified in the strata align temporally (ca. 10.3 ± 0.4 cal ka BP and ca. 8.3 ± 0.3 cal ka BP) with earthquakes on the Teton fault that have been identified in terrestrial and lacustrine paleoseismic records. From ca. 10.4–6.6 cal ka BP core sediments are relatively rich in clay with highly variable magnetic susceptibility and organic carbon content. Deposition during this period was influenced by an evolving stream network and a relatively dry paleoclimate. From ca. 6.6–2.7 cal ka BP core sediments have higher sand and organic carbon contents, suggesting variable fluvial discharge and climate instability. The youngest core records produced a sharp increase in sedimentation rate, sand and organic carbon content, propelled by greater effective moisture, higher lake levels, and increasing watershed vegetation density. Based on clinoform rollover position, water levels at ∼2,046, ∼2,049, ∼2,053, and 2063 m asl characterized Moran Bay during the Holocene. Together, the seismic and core data records indicate a complex and dynamic Holocene lacustrine evolution controlled by fault motion and water level changes.

Integrated groundwater exploration in basement complex terrain for sustainable regional water supply in Abuja, Nigeria

This study integrates geophysical and geological analyses to identify potential areas for regional water supply in newly developed sites and regions lacking coverage from the lower Usuma Dam. Covering an expanse of approximately 5200 km2, high-resolution aeromagnetic data were collected, analyzed, and interpreted alongside thirty-five (35) vertical electrical sounding (VES) data points, utilizing the Schlumberger array with current electrode separations (AB/2) ranging from 100 to 140 m and potential spacing MN/2 varying from 0.25 to 5m. The aeromagnetic data, reduced to the equator, reveal anomalies characterized by variations in magnetic susceptibility, indicative of changes in rock composition. Total magnetic field intensity ranges from 435.7 nT to 568.3 nT, with variations attributed to the presence of diamagnetic materials, specifically magnetite and quartzite in basement rocks. Residual data, ranging from −92 to 41.4 nT and high residual values correspond to granite gneiss and coarse porphyritic biotite hornblende granite. First vertical derivative results expose lineaments with lengths ranging from 894.4m to 11.627 km, supported by tilt derivative lineaments of 1.131–11.400 km these delineate potential zones for urban and regional groundwater supply, emphasizing the role of lineaments and faults in controlling structural geometry for groundwater flow. Geological mapping affirms high fracturing with conjugate faults in the area. Interpreted VES curves identify 65.7% as H-type, 22.9% as KH, and 5.7% as QH curves, with HK- and A-type curves at 2.9%. Overburden thickness varies from 6 to 44 m at specific VES points. Iso-resistivity maps exhibit high resistivity values (6000 to 9000 Ωm) due to geological outcrops, while low resistivity values result from a partially or highly fractured basement. Recommendations include drilling 31 VES points for regional water supply in Abuja's urban area, offering a diversified water source and reducing dependence on potentially vulnerable surface water supplies.

Seasonal and Spatial Variations of Magnetic Susceptibility of Street Dust in Several Cities of Isfahan Province and their Relationship with the Concentration of Selected Heavy Metals

Seasonal and Spatial Variations of Magnetic Susceptibility of Street Dust in Several Cities of Isfahan Province and their Relationship with the Concentration of Selected Heavy Metals

Optimized analysis of the AC magnetic susceptibility data in several spin-glass systems using the Vogel–Fulcher and Power laws

In spin-glasses (SG), the relaxation time τ (=1/2πf) vs Tf data at the peak position Tf in the temperature variation of the ac magnetic susceptibilities at different frequencies f is often fit to the Vogel–Fulcher Law (VFL): τ = τ0 exp[Ea/kB(Tf − T0)] and to the Power Law (PL): τ = τ0* [(Tf−TSG)/TSG]−zυ. Both of these laws have three fitting parameters each, leaving a degree of uncertainty since the magnitudes of the evaluated parameters τ0, Ea/kB, τ0*, and zυ depend strongly on the choice of T0 and TSG. Here, we report an optimized procedure for the analysis of τ vs Tf data on seventeen SG systems for which we could extract such data from published sources. In this optimized method, the data of τ vs Tf are fit by varying T0 in the linear plots of Ln τ vs 1/(Tf − T0) for the VFL and by varying TSG in the linear plot of Ln τ vs Ln (Tf − TSG)/TSG for the PL until optimum fits are obtained. The analysis of the associated magnitudes of τ0, Ea/kB,τ0*, and zυ for these optimum values of T0 and TSG shows that the magnitudes of τ0*, τ0, and zυ fail to provide a clear distinction between canonical and cluster SG. However, new results emerge showing Ea/(kBT0) < 1 in canonical SG, whereas Ea/(kBT0) >1 for cluster SG systems, and the optimized T0 < optimized TSG in all cases. Although some interpretation of these new results is presented, a more rigorous theoretical justification of the boundary near Ea/(kBT0) ∼ 1 is desired along with testing of these criteria in other SG systems.

Magnetodielectric Material for VHF Antenna Devices Tunable by a Low DC Magnetic Field

This study presents the performance of a magneto-dielectric material (MDM) specially developed to enable the tunability of antenna devices operating in the VHF band. A current flowing through the sample, which creates a DC magnetic field inside the sample with the same symmetry as the magnetic domains, controls the magnetic susceptibility variation of the MDM. By changing the magnetization state of the MDM with a low DC magnetic field of 740 A.m-1, a tunability of 40% can be observed. The MDM tunability at VHF frequencies is also highlighted by microwave measurements for different magnetization states.

Centennial scale temporal responses of soil magnetic susceptibility and spatial variation to human cultivation on hillslopes in Northeast China

Soil loss is a significant environmental issue that causes soil degradation and threatens national food security in the black soil region of Northeast China. The magnetic susceptibility (MS) technique is a promising method for evaluating soil loss and estimating soil redistribution. In this study, undisturbed soil samples were selected from four typical black soil cropland slopes with 110a, 60a, 30a, and 20a cultivated durations at 10 cm intervals from the surface to a depth of 50 cm to measure soil MS. Based on measurable magnetic indexes, a quantitative relationship between MS and cultivation duration was constructed. The results indicated that: (1) The MS showed an approximate trend, namely 110a < 60a < 20a < 30a < 0a, the longer the sloping land was cultivated, the smaller the MS. (2) The reduction rate of χlf on the surface and underlying soil ranged from 1.57 to 3.27 and was also enhanced in the topsoil. (3) The relative difference value of MS among cultivation durations were greater at the lower slope than at the upper and middle slopes for all selected slopes; however, all positions became nearly constant after 50a of cultivation; (4) MS values substantially correlated in power function with cultivation duration on the entire slope and on three slope positions with r2 values from 0.50 to 0.86 and root mean square error values from 0.21 to 0.41. Soil MS in croplands varied with cultivation duration and was directly proportional to the increase in cultivation duration, which was used to establish soil redistribution and erosion patterns. The results of this study demonstrate that MS is a credible index for quantifying soil loss during continuous tillage at the centennial scale.

Analysis of the geothermal formation mechanisms in the Gonghe Basin based on thermal parameter inversion

Gonghe Basin is the most critical distribution area of hot dry rock (HDR) geothermal resources in China. Geophysical results (resistivity, velocity, density, etc.) provide an indirect way to image the spatial distribution to understand its genesis, which has a multisolution problem. However, heat flow and thermal conductivity are the most direct and reliable evidence to reveal the distribution of geothermal resources. The conventional thermal conductivity and heat flow obtained based on geologic surveys and rock samples are highly accurate, but it is challenging to characterize the regional distribution characteristics. In this paper, we develop the heat transfer adaptive finite-element equation parameter inversion workflow to invert the thermal parameters and analyze the geothermal formation mechanisms in the Gonghe Basin. First, the synthetic model test verifies that our inversion process has reliable accuracy and strong antinoise ability. For the Gonghe Basin HDR geothermal example, we use high-precision aeromagnetic data to estimate the Curie depth using the improved Parker-Oldenburg method. Then, the regional conductivity thermal and temperature field can be established according to the empirical formula as the initial input model for the inversion procedure. In addition, we collect the temperature data of six HDR geothermal wells across the Gonghe-Guide Basin as a priori constraint information. Combined with the inverted thermal parameters (thermal conductivity, geothermal gradient, and heat flow), geologic structure, and geophysical result, we infer that the high thermal conductivity layer at a depth of 5–10 km provides the main deep heat source channel and the shallow low thermal conductivity fine sandstone layer of Neogene provides good caprock protection for forming a high-temperature geothermal reservoir.

Thermomagnetic cooling of current carrying micro-wire in ferrofluid: Two-phase approach

Thermomagnetic convection is a controlling phenomenon for heat-transfer in ferrofluids. It depends upon the magnetic field gradients, variation in magnetic susceptibility, particle concentration and temperature gradients. This article presents the effect of these parameters on cooling of a current carrying micro-wire in ferrofluid with a focus on magnetophoresis effects. A two-phase Euler-Euler model is developed. The predictions of this model are compared with experimental results and predictions from a single-phase ferrofluid model. For ferrofluid with volume fraction of φ = 0.02, the predicted average wire temperature from the Euler-Euler two-phase model is approximately 1 K lower than the measured wire temperature,while the single phase model is 5 K higher. Under identical magnetic field and heat flux conditions, variations in the particle concentration are found to have a non-negligible effect on thermomagnetic convective cooling. The maximum temperature of the wire for φ = 0.01 ferrofluid is significantly increased by 10 K and greater enhancement to cooling is observed in the case of φ = 0.04, where the inception of thermomagnetic cooling is advanced. Correspondingly, significantly different thermal and velocity fields are observed for different volume fractions. The simulations show different regimes of heat transfer. During the first few hundred milliseconds after applying electrical current, a thin boundary layer develops near the wire surface and the colder region is thermally stratified. At larger time, dispersion of ferro-particles between colder and hotter regions produces concentration gradients which affect the thermal and velocity fields. Eddies generated by thermomagnetic convection are found to form at the bottom of the vertical wire and retain their structure as they are convected upwards by natural convection. The particle concentration at the wire surface (φws) varies from 0.0188 to 0.0260 for an initial volume fraction (φ) of 0.02. This variation disturbs the thermal boundary layer and generates thermal vortices around the heated wire that differ from single-phase model predictions.

Benthic biota (nummulites) response to a hyperthermal event: Eccentricity-modulated precession control on climate during the middle Eocene warming in the Southern Mediterranean

Earth's future environment depends critically on how the marine ecosystems react to the current greenhouse conditions. Past warming events from the Middle Eocene can shed light on the nature of these reactions. Middle Eocene sedimentary archives from the Tethyan margins record the Middle Eocene Climatic Optimum (MECO) with varying carbon isotope excursions from site to site. The present study integrates stable isotopes, the abundance of benthic fauna, and astrochronology to look for the timing of the MECO peak warming and the maximum abundance of nummulites in the Southern Mediterranean (Tunisia). A mesotrophic environment during the lower Bartonian with high eustatic sea level promotes the formation of a shallow water carbonate platform in central Tunisia from 40.6 Ma to 39.8 Ma. Nummulites occur in low abundance in the Lower Reneiche Limestone unit (LRL, Bey et al., 2015) from 40.6 to 40.2 Ma, then increase, reaching maximum abundance at the Upper Reneiche Limestone unit (URL, 40.1 to 40 Ma). Maximum accumulation of nummulites and negative excursion of δ18O in the URL occurred during the MECO's warming peak (40.07 to 40 Ma), 200 kyr after the middle Eocene third-order maximum flooding surface. The nummulitic beds represent warmer climates and higher sea levels (arid to semi-arid climate), and the short marl intervals reflect enhanced detrital input (humid climate and lower sea level). The eccentricity modulations were extracted using a lowpass filter applied on a wide-band precession filter then we computed the instantaneous amplitude using Hilbert Transform. The Spearman-rank correlation assesses the potential introduction of amplitude modulations during tuning. Power Decomposition Analysis (PDA) indicates a dominant short eccentricity forcing on the regional climate during the MECO with a minor obliquity component. Variations in magnetic susceptibility and CaCO3 content suggest a combined control of climate and sea-level cycles controlled by eccentricity-modulated precession cycles.

Geological Structures Controlling Au/Ba Mineralization from Aeromagnetic Data: Harrat ad Danun Area, Saudi Arabia

Positive and negative magnetic anomalies occupied the total aeromagnetic (TM) map of the Harrat ad Danun area, Saudi Arabia. Reduction to the pole (RTP) maps display the range of magnetic values (−312.4 to 209.4 nT) that vary in shape, size, and magnitude. These anomalies generally follow the NNW–SSE (Red Sea axis trend), NE–SW, and NNE–SSW trends. The NNW-SSE linear negative and positive magnetic anomalies could be brought on by buried faults, shear zones, or subsurface dikes. In the central part, the position of Au and Ba mineralization was connected to this trend. It is concluded that the principal structures are represented by the NNW–SSE, NE–SW, and NNE–SSW tendencies. Based on gridded RTP magnetic data, the 2-D power spectrum was computed and revealed the frequency of the near-surface and deep magnetic components. It is believed that the depths of the shallow and deep magnetic sources are typically 80 m and 570 m, respectively. Additional negative and positive magnetic anomalies with varied amplitudes and frequencies, trending in the NNW–SSE, ENE–WSW, and NE–SW directions, are seen when the high-pass and low-pass maps are closely examined. Many faults in various directions cut into these anomalies. The occurrence of negative linear magnetic anomalies (−36.6 nT to −137.3 nT) at this depth (80 m) is also confirmed by this map. The TDR filter and the Euler deconvolution method were used to identify the horizontal variations in magnetic susceptibility as well as the source position and depth of magnetic sources. The linear clustering rings are thought to be caused by contacts or faults with depths between 1 m to 474 m that are oriented WNW–ESE, NNE–SSW, and NNW–SSE. These faults or contacts are thought to be particularly prominent in the western, eastern, southern, northern, and central zones. The majority of felsic and mafic dikes are found to be connected to subsurface structures, showing that three structural trends—WNW–ESE, NNE–SSW, and NNW–SSE—affect the studied area. This demonstrates that important features and shear zones control the majority of Saudi Arabia’s gold deposits. A negative magnetic anomaly that is centered in the area, trending NNW–SSE and crossing the NNE–SSW fault, is connected to the plotted gold and barite mineralization in the study area. This may imply that these two tendencies are responsible for mineralization. This result raises the possibility of mineralization in the NNW negative magnetic feature located in the western part of the area. The occurrence of gold and barite was significantly impacted by the NNW–SSE and NNE–SSW structural lineaments.

Obliquity‐driven mountain permafrost‐related fluvial magnetic susceptibility cycles in the Quaternary mid‐latitude long‐term (2.5 Ma) fluvial Maros Fan in the Pannonian Basin

Magnetic susceptibility (MS) of the Quaternary long‐term mid‐latitude Maros fluvial fan (Pannonian Basin) was recorded to understand the stratigraphical features of source‐proximal fluvial depositional settings. Three fully cored 500‐m‐deep boreholes were sampled at 0.5‐m intervals; low‐field and frequency dependent MS were measured, and complementary hysteresis and SEM‐EDAX investigations were performed on selected samples. Logged susceptibility data were also used to log correlations established by a simultaneous comparison of wireline log and laboratory measurements. Time‐series analyses of the susceptibility records reveal a ~41‐ka and ~100‐ka cyclicity. Towards the source‐distal sections the intensity of the ~41‐ka cycles decreases, while that of the ~100‐ka cycles remains strong. Stratigraphical and spectral similarities were observed between the Maros fluvial fan and Chinese loess records; however, based on complementary magnetic data, the magnetic phase of the Maros Fan sections is related to the detrital magnetite that originates from the catchment during early postglacial permafrost degradations. The amplification of the ~41‐ka cycles can be attributed to the very high susceptibility values in source‐proximal settings and to the special stratigraphical feature of the distributive fluvial systems. This comprises the increased avulsion frequency on the fluvial fans in ‘glacial recession periods’, in concert with the ‘early postglacial’ occurrence of the permafrost‐related magnetite originating from the catchment. As a local phenomenon, this is significant since it records the obliquity‐driven variations in permafrost development in a catchment. However, fluvial and alluvial fans are widespread depositional landforms within the Eurasian mountain range and were possibly the same during the Quaternary deglaciations. Thus, obliquity‐driven magnetic susceptibility variations in source‐proximal fan deposits attached or adjacent to regions of loess deposition should also be considered when scanning for potential source material of aeolian deposits.

Compensation temperature and hysteresis behaviors of a graphene-like bilayer: Monte Carlo Study

Using the Monte Carlo method, the compensation temperature and hysteresis loops of a ferrimagnetic mixed spin-3/2 and spin-5/2 Ising-type graphene-like bilayer are investigated induced by different physical parameters such as crystal field, exchange coupling, external magnetic field, and temperature. The variations of magnetization, magnetic susceptibility, specific heat, and internal energy with the change of temperature are discussed. In addition, we also plot the phase diagrams including transition temperature and compensation temperature. Finally, multiple hysteresis loops under certain parameters are given.

Applicability of Composite Magnetic Membranes in Separation Processes of Gaseous and Liquid Mixtures-A Review.

Recent years have shown a growing interest in the application of membranes exhibiting magnetic properties in various separation processes. The aim of this review is to provide an in-depth overview of magnetic membranes that can be successfully applied for gas separation, pervaporation, ultrafiltration, nanofiltration, adsorption, electrodialysis, and reverse osmosis. Based on the comparison of the efficiency of these separation processes using magnetic and non-magnetic membranes, it has been shown that magnetic particles used as fillers in polymer composite membranes can significantly improve the efficiency of separation of both gaseous and liquid mixtures. This observed separation enhancement is due to the variation of magnetic susceptibility of different molecules and distinct interactions with dispersed magnetic fillers. For gas separation, the most effective magnetic membrane consists of polyimide filled with MQFP-B particles, for which the separation factor (αrat O2/N2) increased by 211% when compared to the non-magnetic membrane. The same MQFP powder used as a filler in alginate membranes significantly improves water/ethanol separation via pervaporation, reaching a separation factor of 12,271.0. For other separation methods, poly(ethersulfone) nanofiltration membranes filled with ZnFe2O4@SiO2 demonstrated a more than four times increase in water flux when compared to the non-magnetic membranes for water desalination. The information gathered in this article can be used to further improve the separation efficiency of individual processes and to expand the application of magnetic membranes to other branches of industry. Furthermore, this review also highlights the need for further development and theoretical explanation of the role of magnetic forces in separation processes, as well as the potential for extending the concept of magnetic channels to other separation methods, such as pervaporation and ultrafiltration. This article provides valuable insights into the application of magnetic membranes and lays the groundwork for future research and development in this area.

Integrated approach using petrophysical, gravity, and magnetic data to evaluate the geothermal resources at the Rahat Volcanic Field, Saudi Arabia

It is necessary to develop and explore geothermal resources to achieve sustainable development and clean renewable energy around the Globe. Geothermal energy is crucial to the future energy supply to meet the environmentally friendly energy demand of the World. The Rahat Volcanic Field (Kingdom of Saudi Arabia) is the oldest and lengthiest Cenozoic Volcanic Field in the World. It is a dominantly a mature mafic Volcanic Field that holds three major geological events; the historic eruption (1256 C.E.), the five fingers (∼4500–1500 BP), and the seismic swarm (1999 C.E.). These incidents were studied by utilizing geological information and geophysical data sets. Geophysical and geostatistical research includes gravity and magnetic survey data, including different log curves and major elements, obtained from water samples as well as of volcanic rocks obtained by X-ray fluorescence (XRF). To gain an understanding of the subsurface thermal structure, these datasets were analyzed. The primary goal of this study is to identify the prominent potential geothermal resources with the help of an available data set. Findings suggest that beneath the historic eruption site along with the fissure eruption, on the western side, there is a geothermal anomaly with a surface footprint of about 35 km2. Analyzing gravity and magnetic data as well as density and magnetic susceptibility variations in rock samples led to the mapping of this anomaly. It has been inferred through integrated study that statistical analysis of major elements will be helpful to validate the results of the outcome.

On the determination and interpretation of the lithospheric induced magnetisation

We present a new technique for reducing the uncertainties inherent in the interpretation of lithospheric magnetic field observations over the Earth. This technique, without involving iterations, provides an improved estimate of the depth-integrated magnetic susceptibility of the crust as compared to previous approaches. Departing from the normal practice of using observations at specific locations, we model directly Gauss coefficients of the lithospheric magnetic field and use an a-priori initial lithospheric thickness model to circumvent magnetic annihilators (i.e. magnetisation distributions that cannot be determined from magnetic data since they have no impact on the lithospheric magnetic field). Of the several initial magnetic layer models tested, we prefer the model where magnetic thickness is based on the Moho or the regional estimate of the Curie depth when it is shallower than the Moho because it is physically reasonable and produces the fewest artefacts. The method is applied to a recent high-degree lithospheric magnetic field model called LCS-1 derived from CHAMP and Swarm magnetic satellite data. The technique is appropriate for regions where induced magnetisation dominates over remanent magnetisation. We show that high degrees of the final depth-integrated magnetic susceptibility variation are dependent only on the corresponding high degrees of the LCS-1 magnetic field model. Thus, the depth-integrated magnetic susceptibility variation is an important quantity derived in the study which enables readily qualitative interpretation of regional geology.