Anomalies In Magnetic Susceptibility Research Articles

Imaging Pleistocene volcanic edifices along the Egyptian Red Sea margin: Insights from reflection seismics and 3D constrained inversion of gravity and magnetic data

Several volcanic buildups have been documented using gravity and magnetic data at specific locations in the Northern Red Sea (NRS). Most of these volcanoes were never sampled, and only a few were imaged by seismic or bathymetry data. Furthermore, the confidentiality of commercial datasets does not allow adequate knowledge of these structures and their morphology and physical properties. In this study, 2D and 3D seismic reflection data and 3D constrained inversion of magnetic and gravity data have been used to infer densities and magnetic susceptibilities of volcanic features in the central part of the NRS and to evaluate the distribution and geometry. This study indicates that the results of the 3D inverted models show a good fit with the volcanic structures inferred from seismic data and, thus, that the inversion technique adopted can be a reliable tool for detecting other edifices where seismic data are missing. The 3D inverted density and magnetic susceptibility models suggest that at least eight isolated structures with similar gravity and magnetic properties exist in the study area. They are associated with high densities and magnetic susceptibility anomalies with average values of 2700 kg/m3 and 0.025 SI, respectively. These magmatic structures are deeply rooted in the sedimentary cover and emerge at elevations of 100 to >650 m relative to the seabed. They developed in a sector interpreted as containing thinned continental crust, accompanied by the ascension of magma through prominent rift-related normal faults. Magmatic activity likely started in the Pleistocene and continues to the present day.

Magnetoelastic effect of kimberlite host rocks (Yakutsk diamondiferous province)

The purpose of the research is to conduct petro- and paleomagnetic studies of Early Paleozoic rocks of the carbonate basement of a number of diamond deposits in the Yakutsk diamondiferous province in order to study the changes in petrophysical parameter values in the dynamic influence zone of a kimberlite pipe. It is shown that the formation of kimberlite diatremes accompanied by pulsating explosions shifting upwards brings about thermoelastic stress fields in the kimberlite-bearing medium, which are characterized by epigenetic changes and associated petrophysical heterogeneities (petrophysical anomalies). Petromagnetic heterogeneities of burning and stress are, therefore, some of these petrophysical anomalies, within which kimberlite-bearing rocks have contrastingly changed their original magnetic characteristics under the action of thermodynamic processes. Primarily, petromagnetic anomalies are reflected in the changed nature of the anisotropy of magnetic susceptibility: from sedimentary to dyke geotype. In addition, petromagnetic anomalies of magnetic susceptibility can be accompanied by the formation of metachronous natural residual magnetization vectors in kimberlite host rocks. The dimensions of petromagnetic anomalies (petromagnetic heterogeneities) may significantly exceed the size of the kimberlite pipe itself, which facilitates identification and delineation of the most promising areas. Besides, the magnetoelastic effect can create zones close to the kimberlite bodies that are hardly permeable for relatively viscous, protocrystal-rich mafic magmas. This is the reason for their wedging out along petrophysical barriers that is presented by splitting into thin tongues, formation of trap-free windows and corridors, toroidal shafts with sharply increasing thickness in intrusions, etc. Having relatively elevated values of magnetic and density parameters, such forms of igneous formations will be reflected in the observed geophysical fields. Thus, it is reasonable to consider petromagnetic anomalies as an important petrophysical search criterion for the detection of bedrock kimberlite bodies.

Magnetic and Geochemical Properties of Zagreb City Area Soils

This study was performed to derive the first insight into the distribution of low-field volume magnetic susceptibility (MS) throughout Zagreb city, based on in situ field measurements. The most interesting locations were selected for soil sampling and their geochemical contents were determined using ICP-OES. A geostatistical approach was applied to the MS and geochemical results. A median of 0.245 × 10−3 SI units was proposed as the average MS value in Zagreb. The mean concentrations of heavy metals in Zagreb’s soils (in µg/g) are Pb (36.82), Zn (87.77), Cu (30.84), Cd (0.66), Cr (29.04), Co (11.89), and Ni (28.40), and these measurements are relatively low in comparison to the Croatian legislation and the European and world average. Boxplot analyses demonstrate that 45% of the studied elements do not feature any anomalies, while most of the remaining elements indicate only one weak anomaly located at the same site as the MS anomalies. Our statistical analysis found significant correlations between MS and the following elements: Cd, Co, Fe, Mn, Na, Pb, Sb, and Zn. In situ MS measurements proved to be an efficient tool for the initial screening of large areas with elevated concentrations of heavy elements, enabling the cheap and fast assessment of the state of the environment.

Integrated surface geochemical and seismic surveys for hydrocarbon exploration - A case study from southern Poland

Surface geochemical surveys were carried out in the Pawłosiów area in the eastern part of the Carpathian Foredeep. The research included an analysis of the molecular composition of soil gas samples as well as measurements of the calcite content, magnetic susceptibility and pH of soil samples. The results obtained were integrated with a geological-seismic model. Changes in the concentrations of total alkanes C2–C5 in relation to changes in indirect geochemical indicators showed “compensatory” character. This means that in places where alkane concentrations were increasing, negative anomalies of magnetic susceptibility and a decrease in pH values were observed. It may be related to the intensity of the oxidation processes or reduction of the magnetic minerals in, as well as the reduced permeability of, the Miocene layers in the zones analysed. Moreover, the complex geochemical-geophysical interpretation showed a zone of anomalous values of the total C2–C5 alkanes in the Pawłosiów area, which is suitable for prospecting. The research performed proved that a thorough analysis of the seismic record allowing subtle DHI anomalies appearing within the Miocene formations to be located, combined with the use of direct and indirect geochemical indicators, can help in identifying an area in terms of hydrocarbon potential. This applies in particular to this type of foreland basin, within which geological formations lie flat, and positive structures (anticlines) are hardly visible in seismic sections. In this type of structure, hydrocarbons can be accumulated in traps of a hybrid character (conventional and unconventional). The extensive zone of geochemical and geophysical anomalies found in the area of Pawłosiów may indicate the presence of this type of hydrocarbon accumulation.Comprehensive research, including direct and indirect geochemical methods in combination with a seismic survey, allows for a better assessment of the hydrocarbon potential of the studied area.

Electronic structure and physical properties of the candidate topological material GdAgGe

We grew needle-shaped single crystals of GdAgGe, which crystallizes in a noncentrosymmetric hexagonal crystal structure with space group $P\overline{6}$ $2m$ (189). The magnetic susceptibility data for $H \ensuremath{\perp} c$ reveal two pronounced antiferromagnetic transitions at ${T}_{N1}$ = 20 K and ${T}_{N2}$ = 14.5 K. The magnetic susceptibility anomalies are less prominent for $H \ensuremath{\parallel} c$. The transition at ${T}_{N1}$ is accompanied by a pronounced heat capacity anomaly confirming the bulk nature of the magnetic transition. Below ${T}_{N1}$, the electrical resistivity data follows a ${T}^{3/2}$ dependence. In the magnetically ordered state, GdAgGe shows positive transverse magnetoresistance, which increases with decreasing temperature and increasing field, reaching a value of $\ensuremath{\sim}27%$ at 9 T and 10 K. The Hall resistivity data and electronic band structure calculations suggest that both the hole and the electron charge carriers contribute to the transport properties. The electronic band structure displays linear band crossings near the Fermi level. The calculations reveal that GdAgGe has a nodal line with drumhead surface states coupled with a nonzero Berry phase, making it a nontrivial nodal-line semimetal.

Rapid Magnetic Susceptibility Characterization of Coastal Morphosedimentary Units at Two Insular Strandplains in Estonia

Coastal archives of changing hydrometeorological conditions include mineralogical anomalies, such as heavy-mineral concentrations (HMCs) of variable thickness and intensity, which contain varying ferrimagnetic (e.g., magnetite) fractions. As an effective alternative to laborious mineralogical and granulometric analysis, we present the first set of bulk-volume low-field magnetic susceptibility (MS) databases from beach and dune lithosomes in the Western Estonian archipelago: Harilaid cuspate foreland (westernmost Saaremaa Island) and Tahkuna strandplain (northernmost Hiiumaa Island). Readings were conducted both in situ from trench walls and on core subsamples. At the Tahkuna site, late Holocene beach ridges reveal substantially lower values: quartz-dominated dune sequences grade from 5–20 μSI downward to diamagnetically dominated (−1–7 μSI) beach facies. Values are higher (20–140 μSI) in historically reactivated parabolic dunes that are encroaching southward over the strandplain. At the Harilaid site, four beach dune ridges (height: 2–3 m) that span the past 250–300 years show a general increase in mean MS from 320–850 μSI with decreasing age, with peaks of 1000–2000 μSI below the dune crests (depth: ~0.3–0.6 m) likely related to contemporary wind acceleration during ridge aggradation. The highest mineralogical anomalies range from 2000–5500 μSI in the historic dune sections and exceed 8000 μSI along the actively eroding upper-berm segments, typical of HMCs generated by moderate storms. MS anomalies are likely correlated with high-amplitude electromagnetic signal responses in georadar records and provide useful information for optical luminescence sampling strategies. Our study demonstrates that magnetic susceptibility trends provide a useful means of rapidly assessing relative temporal changes in overall wave/wind climates, help identify and correlate discrete anomalies related to extreme events, serve as local beach/dune boundary indicators, and represent potentially quantifiable paleo-energy indices.

Correlation between gravitational and magnetic anomalies and crustal susceptibility in the Three Gorges area, China

The Huangling Anticline, which formed during the Jinning movement, is the structural core of the Yangtze River Three Gorges area. In this study, we investigated the geological structure of the Huangling Anticline through correlation analysis among magnetic, Bouguer gravity, and crustal susceptibility anomalies of the Three Gorges and adjacent areas. Aeromagnetic anomalies, which were processed by reducing to the pole, reveal four main aeromagnetic anomaly regions. Three-dimensional (3D) magnetic susceptibility constrained inversion was used to obtain the susceptibility distribution from 0 to 30 km depth. We focused on the spatial distribution of four major rock masses: Sandouping, Huanglingmiao, Dalaoling, and Xiaofeng. The low susceptibility of the Huanglingmiao rock mass is tentatively explained by the combined effect of weathering and stripping of the upper body and a tectonic ductile shear zone at the bottom.

Experimental Observation of Long-Range Magnetic Order in Icosahedral Quasicrystals.

Quasicrystals (QCs), first discovered in 1984, generally do not exhibit long-range magnetic order. Here, we report on long-range magnetic order in the real icosahedral quasicrystals (i QCs) Au–Ga–Gd and Au–Ga–Tb. The Au65Ga20Gd15i QC exhibits a ferromagnetic transition at TC = 23 K, manifested as a sharp anomaly in both magnetic susceptibility and specific heat measurements, along with an appearance of magnetic Bragg peak below TC. This is the first observation of long-range magnetic order in a real quasicrystal, in contrast to the spin-glass-like behaviors observed for the other magnetic quasicrystals found to date. Moreover, when Gd is replaced by Tb, i.e., for the Au65Ga20Tb15i QC, a ferromagnetic behavior is still retained with TC = 16 K. Although the sharp anomaly in the specific heat observed for the Au65Ga20Gd15i QC becomes broadened upon Tb substitution, neutron diffraction experiments clearly show marked development of magnetic Bragg peaks just below TC, indicating long-range magnetic order for the Au65Ga20Tb15i QC also. Our findings can contribute to the further investigation of exotic magnetic orders formed on real quasiperiodic lattices with unprecedented highest global symmetry, i.e., icosahedral symmetry.

Method to observe the anomaly of magnetic susceptibility in quantum spin systems

In quantum spin systems, a phase transition is studied from the perspective of magnetization curve and a magnetic susceptibility. We propose a new method for studying the anomaly of magnetic susceptibility $\ensuremath{\chi}$ that indicates a phase transition. In addition, we introduce the fourth derivative $A$ of the lowest-energy eigenvalue per site with respect to magnetization, i.e., the second derivative of ${\ensuremath{\chi}}^{\ensuremath{-}1}$. To verify the validity of this method, we apply it to an $S=1/2XXZ$ antiferromagnetic chain. The lowest energy of the chain is calculated by numerical diagonalization. As a result, the anomalies of $\ensuremath{\chi}$ and $A$ exist at zero magnetization. The anomaly of $A$ is easier to observe than that of $\ensuremath{\chi}$, indicating that the observation of $A$ is a more efficient method of evaluating an anomaly than that of $\ensuremath{\chi}$. The observation of $A$ reveals an anomaly that is different from the Kosterlitz-Thouless (KT) transition. Our method is useful in analyzing critical phenomena.

Theoretical study on the anomalies of the magnetic susceptibility in the honeycomb lattice compound Na2Co2TeO6

In this paper, based on ab initio molecular dynamics and the exchange-interaction model, the magnetic order transition phenomenon of ${\mathrm{Na}}_{2}{\mathrm{Co}}_{2}\mathrm{Te}{\mathrm{O}}_{6}$ material under different temperatures is investigated. Our results exclude the effect of lattice distortion as a factor for magnetic susceptibility under different temperatures in ${\mathrm{Na}}_{2}{\mathrm{Co}}_{2}\mathrm{Te}{\mathrm{O}}_{6}$. Furthermore, we found that the charge transfer is not a main factor to effectively explain the magnetic phase transition. We proposed a method based on radial distribution function to analyze the space-charge density (SCD) to explore the thermal fluctuations. Our analysis of SCD implies that the thermal fluctuations induced by the variation of atomic vibration under different temperatures are responsible for the anomalies of magnetic susceptibility in ${\mathrm{Na}}_{2}{\mathrm{Co}}_{2}\mathrm{Te}{\mathrm{O}}_{6}$ below the N\'eel temperature.

Magnetic susceptibility anomalies and inverse magnetic transitions in iron-enriched garnet films

Abstract Anomalous properties both of the dynamic magnetic susceptibility and the spontaneous magnetization of Y 3 - x Fe 5 + x O 12 garnet films have been experimentally observed. The most significant anomalies are the following: (a) an orientational magnetic transition at room temperature in the range of the applied magnetic field of 300–700 Oe; (b) a spontaneous magnetization vector reversal in the temperature range of 110–275 °C and the corresponding jump of the dynamic susceptibility at zero magnetic field; (c) oscillations of the magnetization in the paramagnetic state of the sample and the corresponding jumps of the dynamic susceptibility at the planar magnetic field H = 200 Oe. It has been established that all reported anomalies exhibit an inverse behavior, namely, with decrease of the applied magnetic field (or temperature) a reverse hysteresis of the field (or temperature) dependences both of the dynamic magnetic susceptibility and the spontaneous magnetization is observed. Possible reasons for such a behavior of the measured dependences are also discussed.

Unusual magnetic properties of the polar orthorhombic BiFe0.5Sc0.5O3 perovskite

Magnetic properties of new multiferroic BiFe0.5Sc0.5O3 perovskite which exists in two different orthorhombic polymorphs, the antipolar Pnma and the polar Ima2, were studied using a SQUID-magnetometer technique in magnetic fields up to 50 kOe in the temperature range of 5–300 K. Both polymorphs show a weak ferromagnetic component below the Néel temperature, TN∼220 K. A wide cusp-like anomaly of the temperature dependent magnetic susceptibility was revealed below 200 K. The anomaly is dependent on the magnetic field applied and can be associated with the glassy magnetic behavior of the compound. The best fit of the initial magnetization curves taken at each temperature can be obtained as a sum of two contributions, namely the nonlinear in field and the linear one. The nonlinear contribution appeared to be temperature and magnetic field dependent, which is in a good agreement with the magnetization experimentally obtained as a function of temperature in different magnetic fields applied. Increase of external magnetic field leads to a decrease of the nonlinear contribution to the total magnetic moment.

Assessment of topsoil contamination near the Stanisław Siedlecki Polish Polar Station in Hornsund, Svalbard, using magnetic methods

Topsoil contamination near the Stanisław Siedlecki Polish Polar Station (PPS), Hornsund, Svalbard, has been assessed using magnetic methods supplemented by chemical analyses and microscopic observations. Analysis of magnetic parameters has enabled to evaluate the concentration, magnetic mineralogy, and grain-size distribution of anthropogenic magnetic particles.Heavy-metal contamination near the PPS originates primarily from local sources. Anthropogenic spherical, magnetite-like particles were found near the station, whereas uncontaminated topsoil is devoid of such particles. Magnetic studies indicate that magnetite and goethite are the primary magnetic phases, with magnetite levels being higher in polluted area. Magnetic fraction of contaminated topsoil includes a mixture of single-domain and multi-domain grains, while uncontaminated topsoil contains smaller grains. Results show a clear correspondence between Pollution Load Index and magnetic susceptibility anomalies, and that the areal extent of PPS impact on the environment has not expanded significantly since 2004 (although a new contamination source, the scrap yard, is now present). A comparison of magnetic susceptibility measurements with metal analyses indicates that magnetic methods can be used as a rapid, inexpensive, non-invasive, and sensitive tool for the evaluation of topsoil contamination.

Features of thermal and magnetic properties of nonstoichiometric DyB50 boride: The influence of the magnetic phase transition and crystal electric field

The specific heat, thermal expansion and magnetic properties of polycrystalline sample of nonstoichiometric dysprosium boride DyB50, that was synthesized by boron-thermal reduction of the metal from its oxide in vacuum, were studied at 2–300 K. The measurements revealed a heat capacity and magnetic susceptibility anomalies at about TN ≈ 6.3 K, caused by the transition to an antiferromagnetic state. The anomalies of studied properties of DyB50 at higher temperatures have been ascribed to the influence of crystal electric field (CEF). The scheme of CEF-splitting of Dy3+ ion ground level in boride has been proposed.

The magnetic susceptibility of soils in Krakow, southern Poland

Studies into the magnetic susceptibility have been used to assess the soils contamination in the Krakow area. The results of topsoil (over a 2 × 2 km grid), subsoil (37 shallow holes) and soil samples (112) measurements were presented as maps of soil magnetic susceptibility (both volume and mass) illustrating the distribution of parameters in topsoil horizon (0–10 cm) and differential magnetic susceptibility maps between topsoil horizon and subsoil (40–60 cm). All evidence leads to the finding that the highest values of magnetic susceptibility of soil are found exclusively in industrial areas. Taking into consideration the type of land use, the high median value (89.8 × 10−8 m3kg−1) was obtained for samples of cultivated soils and is likely to be connected with occurrence of fertile soil (chernozem). Moreover, enrichment of soils with Pb and Zn accompanies magnetic susceptibility anomalies in the vicinity of the high roads and in the steelworks area, respectively.

Structural evolution of MnTi0·8Ru0·2O3

Here, we present the structural studies on MnTi1-xRuxO3(x = 0, 0.2) compounds. The role of Ti ions in the magnetism of MnTiO3 was unclear so here this issue has been tried to address. The magnetic susceptibility (χ) data shows that the 3-dimensional magnetic character has been improved in the doped MnTiO3. The x = 0 compound goes paramagnetic to antiferromagnetic phase at a temperature ∼64 K followed by a broad peak at a temperature ∼100 K. But in x = 0.2 compound, the antiferromagnetic transition temperature has been shifted towards the lower temperature to ∼47.5 K with a broad peak at temperature ∼79 K. On the doping of Ru at Ti site a sharp anomaly in the temperature dependent magnetic susceptibility (χ) measurement is observed ∼47.5 K in the case of x = 0.2 compound. This sharp anomaly is attributed to the improved 3D character of magnetism which arises because of the direct exchange interaction between Mn-Ti/Ru ions in addition to the inter-layer super superexchange interaction between Mn-Mn ions via two intervening oxygen ions. It is interesting to note that even though the TN and T2D are at low temperatures compared to the x = 0 compound, the onset temperature of these two temperatures occurs at much higher temperature than as observed in x = 0 compound.

Magnetic mapping and soil magnetometry of hydrocarbon prospective areas in western Ukraine

Magnetic measurements in a number of hydrocarbon structures suggest the existence of local magnetic anomalies with certain nT amplitude reflecting the structure contours of the oil and gas deposits, which could therefore be used as a criterion for identifying hydrocarbon traps. Hydrocarbon migration and the microseepage effect changing the composition of magnetic minerals and reaching as high as the near-surface areas and soils cause local magnetic anomalies and changes in the magnetic properties of soils. Magnetic studies on the Orchovychi oil and gas field, Carpathian Foredeep, Western Ukraine, revealed specific features of the local magnetic field and the magnetic properties of soil. A local magnetic anomaly with amplitude of 6-8 nT and a width of about 4 km was detected in the structure of the magnetic field within the Outer zone of the Carpathian Foredeep. The anomaly relates to hydrocarbon deposit areas with complex morphology. Magnetic susceptibility (MS) of soils in the Orhovychi oil and gas field showed a close correlation with landscape changes. Soils were found to show magnetic susceptibility anomalies in close proximity to productive hydrocarbon areas.

Crystal structure, magnetic and dielectric behavior of h-LuMnxO3±δ ceramics (0.95≤x≤1.04)

Lattice constants, magnetic properties and dielectric behavior of h-LuMnxO3±δ solid solution (0.95≤x≤1.04) of bulk ceramic samples prepared by the solid state reaction method were studied to determine the role of stoichiometry changes on the crystalline structure and magneto-electric coupling. It is found that increasing of Mn content results in reduction of cell volume of h-LuMnxO3±δ ceramics mostly due to shrinkage of a-axis length. The antiferromagnetic interactions of Mn3+ ions weaken with cell volume contraction. A weak ferromagnetic contribution appeared in all samples and extends up to the Neel temperature, TN. Irreversibility in temperature dependent magnetic measurements already reported for stoichiometric compositions of hexagonal RMnO3 oxides appears for all h-LuMnxO3±δ samples right below Neel ordering transition. An increase of magnetic coercive field and magnetization on cooling below TN in samples is observed in field dependent magnetization and rises as x increases. In addition to the antiferromagnetic ordering transition at TN, two anomalies of the temperature dependent magnetic susceptibility and dielectric constant are identified below TN, centered at 69K and 31K respectively, being probably due to inhomogeneity of the crystalline structure inside ceramic grains. Changes of the dielectric constant at TN can be attributed to magneto-electric coupling in the off-stoichiometric hexagonal LuMnxO3±δ lattice. The behavior of the dielectric relaxation follows a thermally activated mechanism with activation energy values characteristic of polaron hoping.

Neutron scattering and μSR studies on a Kondo lattice heavy fermion CeRuSn3

Kondo lattice heavy fermion system CeRuSn3 exhibits anomalies in magnetic susceptibility and specific heat at a temperature T ≈ 0.6 K (much lower than the average Kondo temperature TK ≈ 3.1 K) which are thought to be related to antiferromagnetic ordering or spin-glass transition. Our muon spin relaxation (μSR) data show no clear evidence of long range magnetic order in CeRuSn3 down to 84 mK. However, it reveals a slowing down of spin fluctuations below 0.6 K, and a glassy spin-dynamics seems more appropriate. The inelastic neutron scattering data reveal broad excitations around 6-8 meV due to the crystal field effect.

The Effect of Ce Dilution on the Ferromagnetic Ordering in CeAuGe

Transport and thermodynamic properties of the well-ordered hexagonal CeAuGe compound have been studied. This compound is known to order ferromagnetically at TC = 10 K with well-de ned anomalies in magnetic susceptibility χ(T ), electrical resistivity ρ(T ) and speci c heat Cp(T ) characterising the phase transition. The location of TC has been observed to be unstable and enhanced even in moderate applied magnetic elds. However, the dilution of magnetic species, Ce, with the non-f electron element, La, is shown in this work to achieve a continuous suppression of TC to 0 K. The integrity of the space group and the details of the unit cell occupation are retained throughout the substitution series, as is the high-temperature localized Ce-e ective magnetic moment μeff = 2.54 μB/(mol Ce). Our studies of physical properties down to 0.05 K show a quantum critical form of nonFermi liquid behaviour, characterised by a logarithmic divergence in Cp(T )/T data in the very dilute Ce content.