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A series of high entropy manganite perovskites (La 0. 2 Pr 0. 2 Nd 0. 2 Bi 0·2 Ba 0. 2)MnO 3 , (La 1/6 Pr 1/6 Gd 1/6 Bi 1/6 Sr 1/6 Ba 1/6)MnO 3 , (La 0.2 Nd 0.2 Gd 0.2 Sr 0·2 Ba 0.2)MnO 3 and (La 1/6 Pr 1/6 Nd 1/6 Ca 1/6 Sr 1/6 Ba 1/6)MnO 3 with variable hole concentration at fixed A-site ionic radius ( = 1.253 Å) have prepared by sol-gel technique. Single phase samples were characterized by the powder X-ray diffraction (PXRD), Field Emission Scanning Electron Microscopy (FE-SEM), Energy Dispersive X-ray (EDX) analysis and elemental mapping which confirm the phase purity of the samples, surface morphology, elemental ratio and chemical homogeneity. X-ray photoelectron spectroscopic (XPS) studies reveal the increase of Mn4+ ions systematically with the substitution of hole concentration at A-site. Magnetization study in this high entropy sample with variable hole concentration at fixed = 1.253 Å exhibits several contrasting behaviour compare to the conventional hole doped samples. In these high entropy manganites the variation in critical temperature (T C) does not follow expected trend neither with the hole concentration nor to the cationic size disorder parameter, σ 2. Though the is fixed, there is a slight increase in tolerance factor (f) due to hole variation in B-site. Interestingly, T C variation with f shows similar trend to the hole concentration, which is expected to be increased linearly. The effect of f on T C is rather weaker in comparison to σ 2. The large drop in T C for high entropy system with respect to the conventional manganite is related to the local structural distortion which severely hampers the Mn3+—O—Mn4+ double exchange interaction. The competing magnetic interactions lead to magnetic phase separation as well as Griffith like phase. Spin pinning is noticed for the samples containing six elements in A-site which is independent on hole concentration. Possible spin clustering is also realized above ferromagnetic T C. Careful analysis of the magnetization data suggests that observed anomaly in magnetic behaviour can be ascribed to the local chemical disordering apart from the size disorder parameter. The possible role on magnetic properties of the number of elements occupying in a crystallographic site is emphasized. [ABSTRACT FROM AUTHOR]

The single crystals of the topological material candidate EuZnBi 2 have been grown using flux method, and the magnetic properties have been systematically investigated. Crystal structure analysis confirms that EuZnBi 2 crystallizes in a layered tetragonal structure at room temperature, consisting of alternating ZnBi 4 tetrahedral and Bi planar layers, separated by Eu atoms. The direct current (DC) magnetic susceptibility, alternating current (AC) magnetic susceptibility, and specific heat measurements indicate that a long-range antiferromagnetic order of Eu 2 + develops at T N = 20 K and the magnetic easy axis exists in the layers. It is interesting to note that EuZnBi 2 exhibits a magnetic anomaly below T N , which might be associated with the tilting of Eu moments and spin reorientation. [ABSTRACT FROM AUTHOR]

The Chicxulub impact event at ca. 66 Ma left in its wake the only complex crater on Earth with a preserved peak ring, characterized by a well-developed magnetic anomaly low. To date, little is known about its magnetic properties. The joint Integrated Ocean Drilling Program (IODP) and International Continental Scientific Drilling Program (ICDP) Expedition 364 drill core M0077A revealed that the peak ring consists of uplifted and strongly deformed granitoid basement rocks overlain by a 130-m-thick impact melt and suevite layer. Pre- and postimpact hydrothermal systems affected this basement with maximum temperatures up to 450 °C. We used microscopy, mineral chemistry, temperature-dependent magnetic susceptibility, and hysteresis properties to characterize the magnetic mineralogy of pre-, syn-, and postimpact rocks. Compared to its amount of pure, stoichiometric shocked magnetite, the granitoid basement shows low magnetic susceptibility, which is in line with earlier experimental studies indicating that shock reduces magnetic susceptibility. Cation-substituted magnetite with varying compositions in the melt rocks carries a higher induced and remanent magnetization compared to the basement. In the granitoid basement, magnetite was partially oxidized to hematite by a pre-impact hydrothermal event, but at lithological contacts with high-temperature impact melt rock, this hematite was locally retransformed back to magnetite. Elsewhere in the granitoid basement, the temperature reached in the hydrothermal system was too low for hematite retransformation. It was also too low to anneal all the lattice defects in the shocked magnetite, which likely occurs above 540 °C. The presence of shocked magnetite in the granitoid basement well explains the magnetic anomaly low due to its unusually low induced magnetization. [ABSTRACT FROM AUTHOR]

The spatial distribution of the field of lithospheric magnetic anomalies carries information about its sources—deep tectonic structures—and reflects the processes occurring at mantle depths. Based on the geomagnetic data measured by the CHAMP satellite at an observation altitude of ~290 km, the lithospheric magnetic field parameters over the territory of Africa were calculated. A series of lithospheric magnetic anomalies of the total intensity Ta maps of various scales and degrees have been constructed. The distribution of Ta over the territories of Southern and East Africa is given. An analysis of lithospheric magnetic anomalies maps over the territories of African superplume influence showed good agreement with the existing hypothesis about the passage of the mantle superplume flow from the lower mantle to the upper mantle in the northeast direction and its further continuation under the East African rift zone. The parameters of the anomalous lithospheric magnetic field contain information about the magnetization of the lithosphere deep layers, reflecting the magnetic properties of large regional tectonic structures and the topography of the Curie surface, which is associated with the geothermal regime and tectonic setting at different levels of the lithosphere. This work shows the perspective of the geomagnetic field satellite observations using in the study of the tectonics of active zones and mapping of deep lithosphere heterogeneities in hard-to-reach areas. [ABSTRACT FROM AUTHOR]

Materials exhibiting irreversible phase transitions, leading to changes in their properties, have a potential for novel application in electronic components such as a non‐rewritable high‐security memory. Here, we focused on the two salts, [(9‐triptycylammonium)([18]crown‐6)][Ni(dmit)2] (1) and [(9‐triptycylammonium)([15]crown‐5)][Ni(dmit)2] (2), which featured 2D sheet structures with alternately stacked cation and anion layers. Both salts exhibit similar cation arrangements, however, their anion arrangements differ significantly. The temperature‐dependent magnetic susceptibilities of 1 and 2 were well reproduced by the alternating chain model (JAC1/kB=−306(8), JAC2/kB=−239(3) K) and the Curie‐Weiss model (θ=−3.9(1) K), respectively. 1 experience a reversible phase transition around 40–60 K, causing anomalies in magnetic behavior. Moreover, an irreversible single‐crystal‐to‐single‐crystal phase transition to 1′ undergo at ~381 K, inducing a rearrangement of [Ni(dmit)2]− anions and a resistivity decrease from 6.5×106 to 6.5×102 Ω cm. The susceptibility curve of 1′ was reproduced by a combination of the Curie‐Weiss and dimer models (Jdimer/kB=−407(5), θ=−26.7(5) K). The irreversible transition of 1 is the first example for such supramolecule and [Ni(dmit)2]− system to our knowledge, in opening potential new‐type materials. [ABSTRACT FROM AUTHOR]

We present the results of studying the depths to lithospheric magnetic sources under the Baltic Shield and adjacent territories of the Russian Plate and the Scandinavian Caledonides. The depths have been calculated from the global model of the lithospheric geomagnetic field EMAG2v3 by the centroid method. The minimum depths of the lower boundary of the lithospheric magnetically active layer (30–35 km) were obtained under the frame of the Baltic Shield, that is, the Russian Plate, the northern and southern parts of the Scandinavian Caledonides, the maximum (>45 km), under the Scandinavian Peninsula, in the west of the Svecofennian orogen and the Norrbotten craton. The rest of the territory of the Baltic Shield is characterized by intermediate depths (38–45 km). Based on a comparison of our estimates of the depth of the lower boundary of lithospheric magnetic sources with the currently available models of the distribution of the Moho depth under the study area, it can be seen that for most of the Baltic Shield, the magnetically active layer of the lithosphere is located within the crust, with the exception of two areas under the Svecofennian orogen and the eastern part of the Kola Peninsula. This fact supports the hypothesis that the upper mantle has magnetic properties in regions where positive long-wave anomalies of the geomagnetic field are observed at satellite altitudes. The obtained results show that the western and eastern parts of the Kola Peninsula can differ not only in the velocity structure of the crust and upper mantle, which has been previously established by various seismological methods, but also in the magnetic properties of the upper mantle layer located directly under the crust. [ABSTRACT FROM AUTHOR]

We report the structural and magnetic properties of RNi (R = Dy, Tb1/3Dy1/3Ho1/3, and Gd1/5Tb1/5Dy1/5Ho1/5Er1/5) to investigate the high-entropy effect at the rare-earth site. The lattice parameters are almost unchanged by the increase of configurational entropy, which is due to the successive partial substitution of Dy by a pair of rare earth elements located on both sides of Dy in the Periodic Table. All compounds exhibit ferromagnetic ground states. The replacement of Dy with Tb + Ho, which does not have magnetic interactions in competition with Dy, does not affect the magnetic ordering temperature. Although (Gd1/5Tb1/5Dy1/5Ho1/5Er1/5)Ni shows the Curie temperature close to that of DyNi, an additional magnetic anomaly, which would be a spin reorientation, is observed probably due to the introduction of competing magnetic interactions between R = Gd and Er compounds and R = Tb, Dy, and Ho ones. We have also assessed the magnetocaloric effect, and the configurational entropy dependence of the magnetic entropy change reflects that of the temperature derivative of the magnetic susceptibility. Our analysis suggests the possibility of enhancing magnetocaloric properties by designing the anisotropy of rare-earth magnetic moments in the high-entropy state. [ABSTRACT FROM AUTHOR]

The modification of magnetic and elastic properties of YBaCo4O7 +x (x = 0, 0.1) cobaltites at a slight controlled deviation from stoichiometry (x) has been investigated. The magnetic properties of stoichiometric YBaCo4O7 demonstrate nontrivial behavior, which is inconsistent with the generally accepted notion of phase transitions with long-range magnetic order. Only magnetic moment ΔM = MFC – MZFC induced by an external magnetic field (an analog of thermoremanent magnetization) exhibits anomalies at magnetic phase transition temperatures TN1 and TN2 that coincide with those of Young's modulus anomalies, whereas in the magnetic susceptibility curves taken in the FC and ZFC modes, phase transitions are not discerned. At a small off-stoichiometry (x = 0.1), induced moment ΔM rises by an order of magnitude and a residual ferromagnetic moment of about 10–3 μB arises in the magnetization curves. Two scenarios of the cobalt subsystem magnetic behavior with increasing part of cobalt ions Co3+ have been discussed. It has been found that when YBaCo4O7 +x cobaltites deviate from stoichiometry, the evolution of their magnetic properties is similar to that observed at the transition from Y-based to Ca-based cobaltite. [ABSTRACT FROM AUTHOR]

Monoclinic BiCrO3, synthesized at high pressure and high temperature, presents interesting properties with anomalies of magnetic origin observed around 110 and 80 K, which are associated, respectively, with the rise of a G-type antiferromagnetic structure and the spin reorientation along one of the monoclinic axes. In this study, we report a strong spin–phonon coupling in monoclinic BiCrO3 observed by Raman spectroscopy. The renormalization of the phonon energy confirms the coupling with the magnetic orderings. Interestingly, some phonons exhibit this effect at the rising temperature of the G-type antiferromagnetic ordering, whereas others are sensitive to the second magnetic event. A renormalization model based on the mean-field theory, previously applied to other perovskite compounds, was used to analyze the spin–phonon coupling showing different behaviors associated with each magnetic phase. [ABSTRACT FROM AUTHOR]

We report a systematic evaluation of the magnetic properties of FeAl2O4 focusing on the relationship between the fabrication conditions and its structural characteristics, in order to improve ceramics processing in applications of this material. For this purpose, the most important factor to control is the inversion parameter, expressed as y in the (Fe1−yAly)(Al1−y/2Fey/2)2O4 composition, which is relatively high for the spinel aluminate of a transition metal. The magnetic properties of these samples all show the spin glass phenomenon at low temperatures, and the cusp temperature depends systematically on this y value. This means that the evaluation of these magnetic properties will be an effective way to predict some characteristics of product FeAl2O4. Additionally, this study found an anomaly in the structural and magnetic characteristics of FeAl2O4 fabricated at a low temperature. This is thought to originate in a tiny and a small amount of impurity. It will be key for discussing the quality of chemically synthesized FeAl2O4, which is typically produced at low temperatures. [ABSTRACT FROM AUTHOR]

The relationship between the spatial distribution of the lithospheric magnetic anomalies obtained from the data of the German CHAMP satellite and the marker of tectonic processes caused by the movement of the African superplume is considered. Measurements of the geomagnetic field total intensity by the CHAMP satellite at altitudes of ~290–260 km above the area with coordinates 12°–44° E and 30° S–16° N are used as the data source. Analysis of the maps constructed from these data shows that the distribution of the negative magnetic anomalies is consistent with the dominant northeastern vector of the African superplume mantle flow. Due to the heating of the lithosphere by the mantle superplume substance, when the Curie temperature values near 580° are reached, the magnetized structures of the lower crust losetheir magnetic properties, so the trajectory of the mantle flow is "tracked". The concordance of the lithospheric magnetic anomalies distribution to one of two hypothesis on the Ethiopia/Afar plume and its hotspot position is analyzed: either in the territory of the Afar depression, or in the area of the Main Ethiopian rift. The negative magnetic anomalies are fixed directly above the Main Ethiopian Rift, which confirms the second tectonic hypothesis. According to the available seismic studies of the hotspot area, the P-wave model is quite consistent with the magnetic data: at shallow (<400 km) depths, the zone of the lowest velocities is also concentrated under the Main Ethiopian Rift. [ABSTRACT FROM AUTHOR]

SUMMARY: Quaternary lavas of the Stardalur Caldera, 20 km northeast of Reykjavik, Iceland, create a 27 300 nT magnetic anomaly visible in both ground and aeromagnetic surveys. Here, we provide a comprehensive mineralogical and rock magnetic data set to analyse NRM intensities and Koenigsberger ratios of 57 drill-core samples from the critical zone (CZ) of the anomaly high at depths between 41 and 131 m. This extends previous studies and verifies that the anomaly is due to an unusually high intensity of remanent magnetization carried by magnetite. The NRM of the CZ samples was acquired during the Olduvai subchron in a field of at most today's strength. NRM intensities range from 20 to 128 A m–1 with a median of 55 A m–1, and an average of 61 A m–1, respectively, approximately 13–15 times higher than in typical Icelandic basalts (AIB) with an NRM intensity of 4 A m–1. Our new data set shows that the magnetite concentration throughout the CZ basalts is at most twofold higher than in AIB lavas. New data on domain state and TRM efficiency prove that these properties account for an additional factor of at most 2.3. Because magnetite is the most abundant remanence carrier in rocks on Earth, and its remanence acquisition is considered to be extremely well understood, we assert that the remaining discrepancy is a critical enigma in rock magnetism. Results from scanning electron microscopy show that a significant fraction of all CZ magnetite particles have dendritic shapes with grain sizes <1 μm, indicating rapid crystallization. Most large magnetite grains are heavily subdivided by very fine oxidation-exsolution lamellae of ilmenite, and subordinate amount of exsolved spinel as needles, blebs and blades. These common microstructures found throughout the CZ subdivide the initially homogeneous mineral into separate cubicles, here denoted as compartments. The magnetite compartments then have sizes below 1 μm. Hysteresis data, Preisach maps and FORC data consistently confirm that the coercivity distribution is dominated by values above 10 mT, such that multidomain behaviour is of little relevance in the CZ. Between 5 and 20 per cent of the IRM is carried by coercivities above 100 mT, which for magnetite indicates unusually high anisotropy effects in the individual particles. Based on the quantitative analysis of all magnetic contributions to the NRM, we can demonstrate that the average efficiency of NRM acquisition in the CZ Stardalur basalts must be at least a factor 3 higher than in typical basalts. We speculate that this is related to the observed focused compartment size distribution <1 μm, and indicates thermochemical remanence acquisition below the Curie temperature of magnetite. Yet, a detailed physical mechanism for the extreme overefficiency of NRM acquisition remains enigmatic. [ABSTRACT FROM AUTHOR]

Submarine earthquakes have increased in the southwestern Ulleung Basin adjacent to the Korean Peninsula. This study analyzed the gravitational and magnetic properties of the three earthquake-prone areas (Hupo Bank and offshore regions near Pohang and Ulsan) in the basin. The basin was affected by tensile and compressive stresses during the formation of the East Sea. The southern Hupo Bank and the Pohang offshore exhibited high gravity anomalies and strong magnetic anomalies. Hupo Bank was separated from the peninsula and earthquakes in this region have been influenced by crustal fractures that facilitated igneous activities during the formation of the basin. Dense volcanic rocks and seaward dipping reflectors along the Pohang coast and continental slope suggest magmatic activities during the formation of the East Sea. Comparatively, the Ulsan offshore, with a thick sedimentary layer, exhibited a slightly higher gravity anomaly than the surrounding area, but no significant differences in the magnetic anomaly. Sequential tensile and compressive stresses related to the creation of the basin produced complex tectonic structures in this region. The magnetic tilt derivative results suggest that earthquakes were located near magnetic source boundaries. The results show that it is important to monitor earthquake-prone areas with gravity and magnetic anomalies. [ABSTRACT FROM AUTHOR]

The results of a study of the deep structure of the Earth's polar regions based on the interpretation of gravitational anomalies, geomagnetic-field anomalies, and seismological data are presented. Based on measurements on the CHAMP and Swarm satellites, vector models of the magnetic field of the Arctic and Antarctic have been verified. To study the magnetically active zones and roots of the lithosphere observed in near-Earth space, deep sections were constructed. Density sections were obtained from gravitational anomalies, and magnetic sections were obtained from anomalies in the modulus and components of the geomagnetic field. To estimate climate risks, a joint analysis of deep sections with satellite data on variations in the ice cover of the polar regions was carried out. It showed that vertical thermofluid channels play a significant role in the process of ice melting. Distinctive features of melting centers caused by endogenous factors are revealed. The migration paths of fluid flows destroying the ice cover are visualized in sections in the form of channels with reduced magnetic and density properties. The conducted studies allows to understand the possible reasons for the localization of centers of ice and permafrost destruction. It was shown that in the permafrost zones of ancient basement blocks, thermal areas of through taliks arise under the influence of heat flows of fluid-supply channels. Melting areas can be represented by hot spots of ore clusters, within which mineral deposits are concentrated under the influence of hydrothermal flows of mineralized fluids. Studies of the deep structure of the Arctic and Antarctic are of scientific and applied importance for solving exploratory geological and geophysical problems and estimating climate risks. [ABSTRACT FROM AUTHOR]

Modeling gravity and magnetic anomalies over the Chicxulub crater are used to constrain the structure, stratigraphy, and asymmetries. Chicxulub is a multiring ~ 200 km rim diameter structure with a central uplift and well-preserved peak ring. The low relief terrain and physical property contrasts have facilitated geophysical modeling of the structure and impactite deposits. Nevertheless, contrasting models have been obtained due to data resolution limitations, uneven coverage, non-uniqueness solutions, boundary conditions, and heterogeneous/anisotropic media. We employ a multi-technique approach based on regional–residual separation, spectral analysis, first and second derivatives, upward and downward analytical continuations, horizontal gradients, analytical signal, Euler deconvolution, reduction to the pole, and forward modeling to constraint the anomaly sources, geometry and depths. Forward modeling of gravity anomaly favors central uplift flat-top models, whereas magnetic models show irregular shapes with a peak towards the NE, at 4–5 km depth. Analysis shows the effects of intersecting regional anomalies in the semicircular pattern that limit the definition of asymmetries, which constrains impact angle and trajectory, crater structure and pre-existing target features. Models link lateral–vertical density and magnetic property contrasts, distinguishing non-magnetic pre-and post-impact carbonates and carbonate-rich breccias from melt and basement rich breccias, and displaced, fractured impactites and basement uplift. [ABSTRACT FROM AUTHOR]

The physical properties of rocks from the western Okhotsk region were studied and petrophysical maps were constructed to highlight the petrophysical features of tectonic elements of the territory. Petrophysical heterogeneities and anomalies of the respective geophysical fields were compared. The relationship between magnetic anomalies and subsurface rock complexes has been established only for the Mesozoic volcano-plutonic structures of the Okhotsk-Chukotka volcanic belt and partly for the Yudoma–Maya lithotectonic zone. In the ancient blocks of the Aldan–Stanovoy shield and the Uchur–Maya plate, the magnetic anomalies are mainly associated with activation of tectonic–magmatic processes and, to a lesser extent, with the magnetic properties of definite rocks. Inverse relationships have been established between the gravity anomalies and rock density anomalies within the regional gravity low (Tyrkan and South-Verkhoyansk gravity fields) and in the Vilyui syneclise, where gravity high corresponds to the low-density domains. [ABSTRACT FROM AUTHOR]

Mineral exploration in the West Greenland flood basalt province is attractive because of its resemblance to the magmatic sulfide-rich deposit in the Russian Norilsk region, but it is challenged by rugged topography and partly poor exposure for relevant geologic formations. On northern Disko Island, previous exploration efforts have identified rare native iron occurrences and a high potential for Ni–Cu–Co–PGE–Au mineralization. However, Quaternary landslide activity has obliterated rock exposure in many places at lower elevations. To augment prospecting field work under these challenging conditions, we acquire high-resolution magnetic and multispectral remote sensing data using drones in the Qullissat area. From the data, we generate a detailed 3D model of a mineralized basalt unit, belonging to the Asuk Member of the Palaeocene Vaigat Formation. Different types of legacy data and newly acquired geo- and petrophysical as well as geochemical-mineralogical measurements form the basis of an integrated geological interpretation of the unoccupied aerial system (UAS) surveys. In this context, magnetic data aim to define the location and the shape of the buried magmatic body, and to estimate if its magnetic properties are indicative for mineralization. UAS-based multispectral orthomosaics are used to identify surficial iron staining, which serves as a proxy for outcropping sulfide mineralization. In addition, UAS-based digital surface models are created for geomorphological characterization of the landscape to accurately reveal landslide features. UAS-based magnetic data suggest that the targeted magmatic unit is characterized by a pattern of distinct positive and negative magnetic anomalies. We apply a 3D magnetization vector inversion (MVI) model to the UAS-based magnetic data to estimate the magnetic properties and shape of the magmatic body. By means of introducing constraints in the inversion, (1) UAS-based multispectral data and legacy drill cores are used to assign significant magnetic properties to areas that are associated with the mineralized Asuk Member, and (2) the Earth's magnetic and the palaeomagnetic field directions are used to evaluate the general magnetization direction in the magmatic units. Our results suggest that the geometry of the mineralized target can be estimated as a horizontal sheet of constant thickness, and that the magnetization of the unit has a strong remanent component formed during a period of Earth's magnetic field reversal. The magnetization values obtained in the MVI are in a similar range to the measured ones from a drillcore intersecting the targeted unit. Both the magnetics and topography confirm that parts of the target unit were displaced by landslides. We identified several fully detached and presumably rotated blocks in the obtained model. The model highlights magnetic anomalies that correspond to zones of mineralization and is used to identify outcrops for sampling. Our study demonstrates the potential and efficiency of using high-resolution UAS-based multi-sensor data to constrain the geometry of partially exposed geological units and assist exploration targeting in difficult or poorly exposed terrain. [ABSTRACT FROM AUTHOR]

Magnetic contributions to the Earth's magnetic field within the lithosphere are known as magnetic anomalies. Magnetic anomaly maps provide insight on magnetic properties of subsurface rock, geological structures, and plate tectonic history. A small number of studies have analyzed the Phoenix Plate based on magnetic anomaly data. These focused on its tectonic evolution. Here, we study the crustal magnetization of this region and combine the results with additional information from high-resolution bathymetry and complete Bouguer gravity anomalies. We analyzed the horizontal variation of the magnetization in two spectral domains: one that resolves the medium and long wavelengths magnetization components (20–200 km), and another one that focuses on short wavelengths (7–100 km). The obtained magnetization amplitude for the 20–200 km range reveals the presence of NE–SW and NW–SE high trends in magnetization. We attribute these alignments to induced magnetism. For the range of 7–100 km, the magnetization amplitude shows a progressive decrease towards the southern part of the Phoenix Plate. The obtained magnetization pattern and the integration with additional geophysical and geological information indicates a thermal demagnetization of the oceanic crust in the south, possibly caused by the Pacific mantle outflow present in this region. [ABSTRACT FROM AUTHOR]

In southern Alaska, Wrangellia-type magnetic crustal character extends from the Talkeetna Mountains southwest through the Alaska Range to the Bristol Bay region. Magnetic data analyses in the Talkeetna Mountains showed that there are mid-crustal differences in the magnetic properties of Wrangellia and the Peninsular terrane. After converting total field magnetic anomaly data to magnetic potential, we applied Fourier filtering techniques to remove magnetic responses from deep and shallow sources. The resulting mid-crustal magnetic characterization delineates the regional magnetic potential domains that correspond to the Wrangellia and Peninsular terranes throughout southern Alaska. These magnetic potential domains show that Wrangellia-type crust extends southwest to the Iliamna Lake region and that it overlaps the mapped Peninsular terrane. Upon reconsidering geologic ties between Wrangellia, Peninsular, and Alexander terranes, we conclude that Peninsular terrane is part of what we here call Western Wrangellia. Western Wrangellia contains the Lower Jurassic Talkeetna volcanic arc and is similar to Wrangellia of the Vancouver Island area, Canada (Southern Wrangellia), which contains the Lower Jurassic Bonanza volcanic arc. Others have previously made this correlation and proposed that the Talkeetna arc-bearing part of southern Alaska was displaced from the Bonanza arc-bearing part of Canada. We generally agree and propose that about 1000 km of dextral displacement along ancestral Border Ranges fault segments and other faults of south-central Alaska separated Western Wrangellia from Southern Wrangellia. We think this displacement was mostly in the Late Jurassic and earliest Cretaceous, perhaps between about 160 and 130 Ma. [ABSTRACT FROM AUTHOR]

• Induced magnetic moment of stoichiometric YBaCo 4 O 7 exhibits anomalies at magnetic phase transitions. • The anomaly temperatures T N 1 and T N 2 , for induced magnetic moment and Young's modulus coincide well. • When x deviates from stoichiometry, a residual ferromagnetic moment of ∼ 10-2μ B appears in the magnetization curves. • When x deviates from stoichiometry, the anomalies in the Young's modulus rapidly diffuse and vanish. The modification of magnetic and elastic properties of YBaCo 4 O 7 + x (x = 0, 0.1) cobaltite series at a small controlled deviation x = 0, 0.1, 0.2 from stoichiometry has been investigated. The non-stoichiometric cobaltites with x > 0.1 are found to be separated into two structural phases with different values of x under certain synthesis and heat-treatment conditions of the YBaCo 4 O 7+x system (x = 0, 0.1, 0.2). A non-trivial magnetic behavior is observed in stoichiometric YBaCo 4 O 7. Magnetic moment Δ M = M FC – M ZFC induced by an external magnetic field (an analog of thermo-residual magnetization) exhibits anomalies at magnetic phase transition temperatures T N 1 and T N 2 that coincide with Young's modulus anomalies. Conversely, in the magnetic susceptibility curves taken in the FC and ZFC modes, phase transitions are not discerned. When x deviates from stoichiometry, the ratio between two magnetic ions Co3+/Co2+ changes, the induced moment Δ M increases, and a residual ferromagnetic moment of ∼ 10-2μ B appears in the magnetization curves at low temperatures. At a slight deviation from the oxygen stoichiometry in the samples, the structural distortion disappears, and the anomalies in the elastic characteristics near the T N region rapidly diffuse and vanish. It has been found that when YBaCo 4 O 7+x cobaltites deviate from stoichiometry, the evolution of their magnetic properties is similar to that observed at the transition from Y-based to Ca-based cobaltite. Two scenarios of the cobalt subsystem magnetic behavior with an increasing fraction of cobalt Co3+ ions have been discussed. [ABSTRACT FROM AUTHOR]

Polycrystalline samples of DyCo 9 Si 4 with the tetragonal LaFe 9 Si 4 -type structure have been synthesized by arc melting and high-temperature annealing. Results of the magnetization M and specific heat C p measurements show the existence of two magnetic anomalies at T C = 40 K and T m = 20 K. The transition at T C = 40 K is attributed to the ferromagnetic transition of the Co sublattice. The magnetic moments of Dy3+ appear to align gradually below T C , and almost fixed below T m , at which a broad maximum in C p has been observed. Field-dependent M at T = 2 K up to H = 7 T suggested that the magnetic moment of Dy3+ is coupled antiferromagnetically with those of Co, forming a ferrimagnetic structure. Magnetization measurements up to 50 T at low temperatures using a pulse magnet demonstrated a spin-flip transition around H = 20 T, above which the magnetic moments of Co and Dy are in parallel. The spin-flip transition becomes broad with increasing temperature but still remains at T C = 40 K, indicating a strong antiparallel coupling between Co and Dy moments even in the paramagnetic state. The magnetocaloric effect was evaluated from C p and M , and also from the sample-temperature variation in the quasi-adiabatic process with the pulsed magnetic field. The maximum entropy change for the field change from 5 to 0 T was observed at around T = T m with the value Δ S = 5 J/kg K. The maximum temperature of Δ S shifts to higher temperatures in high magnetic fields, resulting in the large value of Δ S = 24 J/kg K at T ∼ T C by the field change from 50 to 0 T. The present results demonstrate that the pulsed-field measurement is a powerful method to evaluate the magnetocaloric effect of materials. ● Physical properties of DyCo 9 Si 4 are reported for the first time. ● Step-like increase of the magnetization curve is observed at low temperature. ● Antiparallel coupling of Dy/Co magnetic moments remains in the paramagnetic state. ● Pulsed field measurement enables a quick and reliable magnetocaloric evaluation. ● Large magnetocaloric effect of 24 J/kg K is observed at T = 40 K. [ABSTRACT FROM AUTHOR]

We have successfully grown large and good-quality single crystals of the La 0.75 Sr 0.25 Cr 0.90 O 3 − δ compound using the floating-zone method with laser diodes. We investigated the crystal quality, crystallography, chemical composition, magnetic properties and the oxidation state of Cr in the grown single crystals by employing a combination of techniques, including X-ray Laue and powder diffraction, scanning electron microscopy, magnetization measurements, X-ray photoelectron spectroscopy and light absorption. The La 0.75 Sr 0.25 Cr 0.90 O 3 − δ single crystal exhibits a single-phase composition, crystallizing in a trigonal structure with the space group R 3 ̄ c at room temperature. The chemical composition was determined as La 0.75 Sr 0.25 Cr 0.90 O 3 − δ , indicating a significant chromium deficiency. Upon warming, we observed five distinctive characteristic temperatures, namely T 1 = 21.50(1) K, T 2 = 34.98(1) K, T 3 = 117.94(1) K, T 4 = 155.01(1) K, and T N = 271.80(1) K, revealing five distinct magnetic anomalies. Our magnetization study allows us to explore the nature of these anomalies. Remarkably, the oxidation state of chromium in the single-crystal La 0.75 Sr 0.25 Cr 0.90 O 3 − δ , characterized by a band gap of 1.630(8) eV, is exclusively attributed to Cr3＋ ions, making a departure from the findings of previous studies on polycrystalline materials. [Display omitted] We present a La 0.75 Sr 0.25 Cr 0.90 O 3 − δ single crystal that we successfully grew, along with magnetization data revealing five distinct features and XPS measurements confirming the presence of a solely Cr3＋ oxidation state. • We have successfully grown single crystals of La 0.75 Sr 0.25 Cr 0.90 O 3 − δ. • The room-temperature structure of La 0.75 Sr 0.25 Cr 0.90 O 3 − δ was identified as trigonal. • We observed five distinct magnetic anomalies in La 0.75 Sr 0.25 Cr 0.90 O 3 − δ. • We have discussed the nature of these magnetic anomalies. • The oxidation state of chromium in La 0.75 Sr 0.25 Cr 0.90 O 3 − δ is solely +3. [ABSTRACT FROM AUTHOR]

The structures of hexafluoroacetylacetonate complexes of Cu(II)–Cu(hfac)2– with nitroxide radicals LR1/R2, where R1 and R2 are alkyl substituents in the 1,3-pyrazole moiety are studied by X-ray crystallography. It is found that solid phases of all [Cu(hfac)2LR1/R2] are formed by polymeric chains whose common structural motif is a ditopic bridging coordination of paramagnetic ligands in the head-to-head fashion. The study of the temperature structure dynamics and the related change in the temperature dependence of the effective magnetic moment of the complex shows that changes in both R1 and R2 can substantially affect not only the possibility of the appearance of magnetic anomalies on the temperature curve of the effective magnetic moment but also its shape. [ABSTRACT FROM AUTHOR]

Effective quantitative methods for integrating multiple inverted physical property models are necessary to increase the value of information and advance interpretation further to produce interpretable geology models through geology differentiation. Geology differentiation is challenging in greenfield exploration areas where specific a priori geological information is scarce. The main problem is to identify geological units quantitatively with appropriate 3-D integration of these models. The integration of multiple sources of information has been conducted with different unsupervised machine learning methods (e.g. clustering), which can identify relationships in the data in the absence of training information. For this reason, we investigate the performance of five different clustering methods on the identification of the geological units using inverted susceptibility, density, and conductivity models that image a synthetic geological model. We show that the correlation-based clustering yields the best results for the geology differentiation among those investigated by identifying the correlation between physical properties diagnostic of each unit. The result of the differentiation is a quasi-geology model, which is a model that represents the geology with inferred geological units and their spatial distribution. The resulting integrated quasi-geology model demonstrates that individually inverted models with minimal constraints have sufficient information to jointly identify different geological units. [ABSTRACT FROM AUTHOR]

Mineral exploration in the West Greenland flood basalt province is attractive because of its resemblance to the magmatic sulphide-rich deposit in the Russian Norilsk region, but it is challenged by rugged topography and partly poor exposure for relevant geologic formations. On northern Disko Island, previous exploration efforts have identified rare native iron occurrences and a high potential for Ni-Cu-Co-PGE-Au mineralization. However, Quaternary landslide activity has obliterated rock exposure at many places at lower elevations. To augment prospecting field work under these challenging conditions, we acquire high-resolution magnetic and optical remote sensing data using drones in the Qullissat area. From the data, we generate a detailed 3D model of a mineralized basalt unit, belonging to the Asuk Member (Mb) of the Palaeocene Vaigat formation. A wide range of legacy data and newly acquired geo- and petrophysical, as well as geochemical-mineralogical measurements form the basis of an integrated geological interpretation of the unoccupied aerial system (UAS) surveys. In this context, magnetic data aims to define the location and the shape of the buried magmatic body, and to estimate if its magnetic properties are indicative for mineralization. High-resolution UAS-based multispectral orthomosaics are used to identify surficial iron staining, which serve as a proxy for outcropping sulphide mineralization. In addition, high-resolution UAS-based digital surface models are created for geomorphological characterisation of the landscape to accurately reveal landslide features. UAS-based magnetic data suggests that the targeted magmatic unit is characterized by a pattern of distinct positive and negative magnetic anomalies. We apply a 3D magnetization vector inversion model (MVI) on the UAS-based magnetic data to estimate the magnetic properties and shape of the magmatic body. By means of using constraints in the inversion, (1) optical UAS-based data and legacy drill cores are used to assign significant magnetic properties to areas that are associated with the mineralized Asuk Mb, and (2) the Earth's magnetic and the paleomagnetic field directions are used to evaluate the general magnetization direction in the magmatic units. Our results indicate that the geometry of the mineralized target can be estimated as a horizontal sheet of constant thickness, and that the magnetization of the unit has a strong remanent component formed during a period of Earth's magnetic field reversal. The magnetization values obtained in the MVI are in a similar range as the measured ones from a drillcore intersecting the targeted unit. Both the magnetics and topography confirm that parts of the target unit were displaced by landslides. We identified several fully detached and presumably rotated blocks in the obtained model. The model highlights magnetic anomalies that correspond to zones of mineralization and is used to identify outcrops for sampling. Our study demonstrates the potential and efficiency of using multi-sensor high-resolution UAS data to constrain the geometry of partially exposed geological units and assist exploration targeting in difficult, poorly exposed terrain. [ABSTRACT FROM AUTHOR]

The interplay between magnetism and quantum effects has motivated several thermoelectric studies on iron‐telluride yet with little insight on the anomalous features in transport properties near magnetostructural transition temperature (≈70 K). A detailed investigation is carried out on Fe1.1Te by characterizing magnetic, heat capacity, galvanomagnetic, and thermoelectric transport properties to understand the electronic, magnetic, and structural origin of those anomalies. The magnetic susceptibility indicates a bicollinear stripe and short‐range ordering in the antiferromagnetic and paramagnetic domains, respectively. Hall conductivity and transverse magnetoresistance reveal a multicarrier transport impacted by spin fluctuations and magnons. Contributions from phonon‐drag and magnon‐drag are evaluated to understand the origin of the broad peak in antiferromagnetic thermopower. The peak at ≈50 K and the insignificant entropy contribution from the magnonic heat capacity support the phonon‐drag as the origin. The field‐dependent enhancement of thermal conductivity must be associated with field‐dependent spin‐phonon coupling modification. The field‐induced thermopower reduction can be attributed to the suppression of magnons or paramagnons, as evidenced by the magnetic susceptibility data. Above 70 K, the thermal conductivity drops sharply due to the structural change modifying phonon modes. Understanding these properties originated from the spin, and quantum effects are instrumental for designing high‐performance spin‐driven thermoelectrics. [ABSTRACT FROM AUTHOR]

Microscopic structures and magnetic properties are investigated for Fe5−xGeTe2 single crystal, recently discovered as a promising van der Waals (vdW) ferromagnet. An Fe atom (Fe(1)) located in the outermost Fe5Ge sublayer has two possible split‐sites which are either above or below the Ge atom. Scanning tunneling microscopy shows √3 × √3 superstructures which are attributed to the ordering of Fe(1) layer. The √3 × √3 superstructures have two different phases due to the symmetry of Fe(1) ordering. Intriguingly, the observed √3 × √3 ordering breaks the inversion symmetry of crystal, resulting in substantial antisymmetric exchange interaction. The temperature dependence of magnetization reveals a sharp magnetic anomaly suggesting helical magnetism of the Fe5−xGeTe2 due to its non‐centrosymmetricity. Analytical study also supports that the observed ordering can give rise to the helimagnetism. The work will provide essential information to understand the complex magnetic properties and the origin of the new vdW ferromagnet, Fe5−xGeTe2 for future topology‐based spin devices. [ABSTRACT FROM AUTHOR]

• Sr 4 CoZnFe 36 O 60 has U-type hexaferrite crystal structure. • Ferrimagnetic Sr 4 CoZnFe 36 O 60 exhibits three magnetic phase transitions. • Giant permittivity has origin in non-homogeneous conductivity. • Magnetocapacitance effect was attributed to magnetoresistance. • Two magnetic excitations (domain wall motions) discovered below 1 GHz. Sr 4 CoZnFe 36 O 60 ceramics with U-type hexaferrite crystal structure were for the first time prepared and their structural, dielectric, magnetic and magnetoelectric properties were characterized. Broadband dielectric spectra (1 Hz −1 GHz) showed giant permittivity due to two Maxwell-Wagner dielectric relaxations whose frequencies follow the Arrhenius law. These relaxations are caused by inhomogeneous conductivity in the ceramic grains and their boundaries. Temperature and magnetic field dependences of magnetization revealed ferrimagnetic phase transition at T c1 = 635 K and other two magnetic phase transitions at T c2 = 305 K and T c3 = 145 K. Magnetoelectric measurement at 10 K revealed only small polarization 35 nC/m2 which has probably extrinsic origin, so the sample is probably not multiferroic. The observed magnetocapacitance effect (-0.8 %) was attributed to the magnetoresistance (-4 %) caused by non-homogeneous conductivity of the ceramics. High-frequency magnetic permeability measured up to 1.8 GHz evidences the Curie-Weiss behavior above T c2 and T c3 and two magnetic field-dependent excitations which exhibit anomalies at magnetic phase transitions. We attributed these excitations to the magnetic domain wall dynamics. [ABSTRACT FROM AUTHOR]

The study is concerned with structural rearrangements in the crystals of heterospin complexes Cu(hfac)2 with nitroxide radicals LR (hfac is hexafluoroacetylacetonate, LR is 2-(1-R-1H-pyrazol-4-yl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazole-3-oxide-1-oxyl, R is Et or Allyl) induced by increasing pressure from 10−4 to ∼1 GPa in the pressure-transmitting medium. An increase in the external pressure to only ∼0.03 GPa leads to the disappearance of the temperature-induced magnetic anomaly observed for these heterospin crystals under ambient conditions. [ABSTRACT FROM AUTHOR]

Magnetic anisotropy has proved effective in characterizing primary, spreading-related magmatic fabrics in Mesozoic (Tethyan) ophiolites, for example in documenting lower oceanic crustal flow. The potential for preservation of primary magnetic fabrics has not been tested, however, in older Palaeozoic ophiolites, where anisotropy may record regional strain during polyphase deformation. Here, we present anisotropy of magnetic susceptibility results from the Ordovician Thetford Mines ophiolite (Canada) that experienced two major phases of post-accretion deformation, during the Taconian and Acadian orogenic events. Magnetic fabrics consistent with modal layering in gabbros are observed at one locality, suggesting that primary fabrics may survive deformation locally in low strain zones. However, at remaining sites rocks with different magmatic origins have consistent magnetic fabrics, reflecting structurally controlled shape preferred orientations of iron-rich phases. Subhorizontal NW-SE-oriented minimum principal susceptibility axes correlate with poles to cleavage observed in overlying post-obduction, pre-Acadian sedimentary formations, indicating that the magnetic foliation in the ophiolite formed during regional NW-SE Acadian shortening. Maximum principal susceptibility axes plunging steeply to the NE are orthogonal to the orientation of regional Acadian fold axes, and are consistent with subvertical tectonic stretching. This magnetic lineation is parallel to the shape preferred orientation of secondary amphibole crystals and is interpreted to reflect grain growth during Acadian dextral transpression. This structural style has been widely reported along the Appalachian orogen, but the magnetic fabric data presented here provide the first evidence for transpression recorded in an Appalachian ophiolite. [ABSTRACT FROM AUTHOR]

Magnetic phase transitions and structure anomalies in solid solutions of double manganites Nd1-xPrxBaMn2O6 obtained for the first time have been investigated by magnetometry and X-ray powder diffraction. It has been shown that the structural anomaly in the form of unit cell volume jump and drastic increase of unit cell parameters ratio а/с is not related to the magnetic or metal-insulator phase transitions. [ABSTRACT FROM AUTHOR]

Floodplain wetlands are complex systems influenced by many natural and anthropogenic operators. Due to the influence of high and varying groundwater table and high organic contents, geophysical prospection in wetland floodplains quickly reaches the limits of its effectiveness. At the Early Medieval canal Fossa Carolina in southwest Germany, a study design employing magnetometry, drillings, sampling, and in situ rock magnetic measurements was used for environmental magnetic interpretation of magnetic anomalies in magnetograms and sediment layers. This approach offers reliable archaeological interpretation of magnetic anomalies and magnetic properties under the site specific sedimentological conditions of a floodplain wetland. It was also found that man‐made magnetic anomalies in the floodplain are due to the genesis of different remanent magnetizations – specifically, greigite (Fe3S4) can cause distinct magnetic anomalies in floodplains that can be recognized readily in surface magnetic data. [ABSTRACT FROM AUTHOR]

In 2011, the discovery of shatter cones confirmed the 28 km diameter Tunnunik complex impact structure, Northwest Territories, Canada. This study presents the first results of ground‐based electromagnetic, gravimetric, and magnetic surveys over this impact structure. Its central area is characterized by a ~10 km wide negative gravity anomaly of about 3 mGal amplitude, roughly corresponding to the area of shatter cones, and associated with a positive magnetic field anomaly of ~120 nT amplitude and 3 km wavelength. The latter correlates well with the location of the deepest uplifted strata, an impact‐tilted Proterozoic dolomite layer of the Shaler Supergroup exposed near the center of the structure and intruded by dolerite dykes. Locally, electromagnetic field data unveil a conductive superficial formation which corresponds to an 80–100 m thick sand layer covering the impact structure. Based on the measurements of magnetic properties of rock samples, we model the source of the magnetic anomaly as the magnetic sediments of the Shaler Supergroup combined with a core of uplifted crystalline basement with enhanced magnetization. More classically, the low gravity signature is attributed to a reduction in density measured on the brecciated target rocks and to the isolated sand formations. However, the present‐day fractured zone does not extend deeper than ~1 km in our model, indicating a possible 1.5 km of erosion since the time of impact, about 430 Ma ago. [ABSTRACT FROM AUTHOR]

Curvelets are multiscale and multidirectional operators that have many applications in image and data processing. Because of the effect of depth and source dimensions on the wavelength (or frequency content) of potential field anomalies, the study of magnetic data in the curvelet domain is of interest. In this paper, the consequences of transforming magnetic data to the curvelet domain are studied using synthetic models and real data for the first time. Based on the results of the theoretical models, we applied the method to airborne and ground magnetic survey data. We show the utility of the curvelet transformation for removing relatively large amounts of noise and its utility as a qualitative method for relatively robust delineation of magnetic sources, especially sources that are close, with overlapping anomalies. In the first step, the data in the curvelet domain are divided into scales or bands. Each scale is then split into multiple sub-bands that have different directional properties. We focus on the scale properties of magnetic data by studying the effects of debilitation or removing some scales in the curvelet domain. The first band (scale 1) of magnetic data in the curvelet domain corresponds to lower frequencies and contributes most to the energy of the signal. Thus, decreasing or removing this scale can highlight detailed (high-frequency) information. By contrast, the highest band has the highest frequency content and contains most of the noise. In this paper, we show that applying the inverse curvelet transform to the middle bands only (after deleting both low and high bands) gives the best results for the purpose of defining the horizontal locations of compact magnetic bodies. [ABSTRACT FROM AUTHOR]

The island of Leka and surrounding skerries expose a complete suite of ophiolitic rocks, which are heavily faulted. Large areas consist of ultramafic rocks, which are locally hydrated and form serpentinites. Faults are commonly fluid pathways and can be areas of increased serpentinization. Because magnetite is a common product of serpentinization such fault zones add to the local magnetic response of the rocks. Here, ground-magnetic data were used in combination with aeromagnetic data to develop models over the major faults across the island. A mapping workflow was developed which uses tilted slabs to represent different zones of magnetization. The magnetic properties of surface-rock samples provided the constraints for the magnetic modeling. Sensitivity tests on the model showed the detection of magnetic fault zones to be limited to depths shallower than one km. Magnetic modeling allowed for an estimation of the magnetization of several major faults. The magnetic zone of one of the largest faults, which forms the boundary between gabbro and ultramafic rocks, had an enhanced magnetization over a width of approximately 200 m. The model is supported by both ground and aeromagnetic data: the first helped in refining the magnetization distribution at shallower depth, the latter allowed for modeling of the deeper part of the fault, indicating the geometry of a listric fault. The total magnetizations of the modeled slabs are well above the background magnetization of the Leka Ophiolite Complex (LOC) determined by modeling and on magnetic property data on >500 samples. This shift towards higher values indicates that serpentinization in some of the fault zones contributes significantly to the magnetic anomalies of the LOC. [ABSTRACT FROM AUTHOR]

The crystal structures of the Gd8Ag19.5(2)Al45.2(2) (Gd4(Ag0.294Al0.706)32Ag0.340) and Ho8Ag21.2(2)Al43.3(2) (Ho4(Ag0.323Al0.677)32Ag0.252) compounds, which adopt the Yb8Cu17Al49-type structure with the space group I4/mmm, have been investigated by means of the X-ray powder diffraction. The structures of the compounds are characterized by the silver/aluminum mixing on several atomic positions and the partial occupancy of silver atoms on one atomic position. dc and ac magnetic data indicate antiferromagnetic properties below 46.5 K for Gd8Ag19.5Al45.2 and 15 K for Ho8Ag21.2Al43.3. In case of RE = Gd an anomaly observed in its magnetic susceptibility at 3.5 K suggests a magnetic transition of the order-order type. A metamagnetic phase transition is detected for RE = Ho. [ABSTRACT FROM AUTHOR]

• The partial α-to-β phase conversion due to thermal stress on cooling is confirmed. • The origin of magnetic anomaly in MnSe might be the 2D short-range FM ordering. • Unexpected magnetic-order-like signal is observed at 16 K in MnS. • The T 1.5 dependence of specific heat implies a weak FM ordering in MnS below 16 K. We have carried out detailed structural, magnetic and thermal properties studies of the Mn(Se, S) system. The detailed structural studies using synchrotron X-ray and neutron diffractions on MnSe confirm the coexistence of cubic and hexagonal phases at low temperature, which shows strong thermal hysteresis suggesting the first-order nature of the transition. Based on the temperature-dependent magnetic susceptibility, we confirmed that the substitution of the sulfur element to selenium critically modified the complex magnetism observed in MnSe. It was to our surprise to observe a magnetic anomaly at 16 K way below the antiferromagnetic order that sets at about 160 K in MnS. Our neutron study at low temperature did not reveal any additional magnetic structure below 16 K. However, the specific heat of MnS shows a clear T1.5 temperature dependence below 16 K, suggesting the possible emergence of a weak ferromagnetic order. [ABSTRACT FROM AUTHOR]

• Linear temperature dependence of the saturation magnetization. • The sublattices magnetization compensation temperature. • Disappearing of the phonon mode in the vicinity of the magnetic transition. • Distribution of iron ions over octahedral and tetrahedral sites. The magnetic properties and Mössbauer spectra of the Y 1.8 Bi 1.2 Fe 3.5 Ga 1.5 O 12 compound were investigated. A linear temperature dependence of the saturation magnetization, hysteresis, and stability of the coercive field in the magnetically ordered state were found. Using the Mössbauer measurements, the distribution of iron ions over octahedral and tetrahedral sites and the concentration of paramagnetic iron ions were determined. Two critical temperatures – the sublattice magnetization compensation temperature and the ferrimagnet–paramagnet transition temperature – were established. The disappear of the phonon mode in the vicinity of the magnetic transition was observed. The experimental data have been interpreted in terms of the spin–lattice interaction model. [ABSTRACT FROM AUTHOR]

We report the structural, magnetic and dielectric properties of polycrystalline samples of double perovskites Sr 2- x Ca x MnTiO 6 (x = 0 and 1) synthesized by the solid-state reaction method. The compound Sr 2 MnTiO 6 (x = 0) could be indexed in both cubic structure (space group Pm 3 ‾ m) and tetragonal structure (space group I 4/ m); whereas by replacing Sr by Ca, i.e., SrCaMnTiO 6 (x = 1) orthorhombic structure space group Pbnm is observed. Along with the differences in the crystal structure of these two compounds, noticeable differences in the physical properties were also observed. The magnetization data of Sr 2 MnTiO 6 reveals magnetic anomaly at T C ⁓ 14 K, whereas the magnetization data of SrCaMnTiO 6 exhibits antiferromagnetic ordering at T N = 7.5 K. The conductivity and dielectric behavior of these samples investigated over a wide frequency range at room temperature exhibits dipolar relaxation. Partial substitution of Ca for Sr in Sr 2 MnTiO 6 results in reduction in crystalline symmetry as the structure changes from cubic/tetragonal to orthorhombic, affecting its magnetic and electrical properties. [ABSTRACT FROM AUTHOR]

The maximum depth of magnetization in the Earth's crust is generally thought to coincide with the Curie temperature of magnetite (580 °C) and is commonly called the Curie depth. A popular approach to estimating the Curie depth is based on comparing the power-spectral density (PSD) of total-field magnetic anomaly data with theoretical expressions that describe the statistical properties of crustal magnetization and its depth distribution. However, the self-affine nature of magnetization (characterized by a power-law exponent in the PSD) renders this problem difficult in practice and several approximate methods have been devised to obtain estimates of the depth distribution and infer Curie depth variations using curve fitting of limited wavenumber ranges of biased PSD estimates. In most studies, however, errors are not carefully propagated through the estimation process and uncertainties in estimated parameters are not reported. In addition, robust spectral estimation techniques are required to map the spectral properties in space at the highest resolution possible and obtain Curie depth maps. Here we investigate the combined use of the robust multitaper spectral estimation technique with a Bayesian formalism to evaluate the recovery of the depth and statistical properties of the buried magnetized layer using a systematic analysis of synthetically generated data. Based on these tests, we come to the conclusion that most Curie depth estimates are not reliable, although it may be possible to obtain more reliable estimates through incorporation of prior information on one or all model parameters. Finally, we suggest that the spectral analysis of magnetic anomaly data may be better suitable to hotter settings, where shallow Curie depth estimates are more robust and in the oceans, where magnetization is likely to be uniform. These studies may also be more useful in retrieving the power-law exponent of magnetization as well as the depth to the top of the magnetized layer. [ABSTRACT FROM AUTHOR]

We implement a spectral-infinite-element method (SIEM) to compute magnetic anomalies by solving a discretized form of the Poisson/Laplace equation. The SIEM combines the highly accurate spectral-element method with the mapped-infinite element method, which reproduces an unbounded domain accurately and efficiently. This combination is made possible by coupling Gauss–Legendre–Lobatto quadrature in spectral elements with Gauss–Radau quadrature in infinite elements along the infinite directions. Our method has two distinct advantages over traditional methods. First, the higher-order discretization accurately renders complex magnetized heterogeneities. Second, since the computation time is independent of the number of observation points, the method is efficient for very large models. We illustrate the accuracy and efficiency of our method by comparing calculated magnetic anomalies for various magnetized heterogeneities with corresponding analytical and commonly used computational solutions. We conclude with a practical example involving a complex 3-D model of an ore mine. [ABSTRACT FROM AUTHOR]

In the European region, the magnetic field at satellite altitudes (∼350 km) is mainly defined by a long-wavelength magnetic low, called the Central European Magnetic Low (CEML) here, located to the southwest of the Trans-European Suture Zone (TESZ). We studied this area through a joint analysis of magnetic and total gradient (∇T) anomaly maps for a range of different altitudes of 5, 100 and 350 km. Tests on synthetic models showed the usefulness of the joint analysis at various altitudes to identify reverse dipolar anomalies and to characterize areas in which magnetization is weak. This way we identified areas where either reversely or normally magnetized sources are locally dominant. At a European scale these anomalies are sparse, with a low degree of coalescence effect. The ∇T map indeed presents generally small values within the CEML area, indicating that the Paleozoic Platform is weakly magnetized. At 350 km of altitude, the TESZ effect is largely dominant: with intense ∇T highs above the East European Craton (EEC) and very small values above the Paleozoic Platform, this again denotes a weakly magnetized crust. Small coalescence effects are masked by the trend of the TESZ. Although we identified sparsely located reversely magnetized sources in the Paleozoic Platform of the CEML, the joint analysis does not support a model of a generally reversely magnetized crust. Instead, our analysis strongly favors the hypothesis that the CEML anomaly is mainly caused by a sharp contrast between the magnetic properties of the EEC and Paleozoic Platform. [ABSTRACT FROM AUTHOR]

Borehole navigation surveys performed using a triaxial fluxgate magnetometer record the change in orientation of the magnetic vector versus depth. Variations in the orientation of the magnetic vector arise from either on- or off-hole magnetic sources. On-hole magnetic sources associated with magnetic property fluctuations in the immediate wall of the borehole (i.e., susceptibility) and (or) remanence polarity changes produce sharp-edged anomalies. Off-hole magnetic sources, caused by a magnetic body near, but not penetrated by, the borehole, produce broad smooth anomalies. Prior to the interpretation of borehole magnetic anomaly logs, data corrections must be applied. Data from each of the magnetic and tiltmeter sensors must be corrected for differential gain, base value offset, and nonorthogonality. By using a probe with two sets of triaxial fluxgates, it is possible to detect along hole magnetic field rotations, which compromise the borehole navigation calculations. After rotation into geographic coordinate space, borehole vector magnetic data from the Chicxulub impact crater in Mexico showed no evidence for any systematic change of magnetic property versus depth. What was originally interpreted as reversal stratigraphy has proved to be minor changes in borehole geometry. Borehole magnetic data from a borehole through the Stratmat deposit, located in the Bathurst mining camp, New Brunswick, show strong off-hole and on-hole anomalies associated with the pyrrhotite-rich ore bodies. [ABSTRACT FROM AUTHOR]

We have studied the magnetic properties of Cd1 –xFexCr2S4 solid solutions in the FeCr2S4–CdCr2S4 system in the range 0.6 ≤ x < 1. Measurements were made in the temperature range 5–300 K in static (≤7960 A/m) and ac (10, 100, and 1000 Hz) magnetic fields of 79.60 A/m peak. All of the materials have been shown to exhibit low-temperature magnetic anomalies due to the effect of orbital ordering in FeCr2S4, a basic component, at 10 K. [ABSTRACT FROM AUTHOR]

Local magnetic fields Hloc exceeding significantly the magnetic fields produced by nuclear magnetic moments (a few gauss) have been detected in bismuth compounds with valence s and p electrons, which are generally believed to be diamagnetic, by the methods based on measuring the parameters of nuclear quadrupole interactions. Anomalies in the magnetic properties of BiSbO4 and Bi4Si3O12 were clearly manifested when analyzing the line shapes in their 209Bi NQR spectra. The quartet of lines for the lower transition ν1 (Δm = 1/2–3/2) in the spectrum of Bi4Si3O12 in zero external magnetic field and the doublets for the lines of all other transitions in the spectrum of BiSbO4 at unique crystallographic positions of bismuth atoms in the crystal lattices of the compounds suggest a magnetic nature of the splittings. The most probable values of Hloc in these compounds are those in the range from 40 to 100 G. [ABSTRACT FROM AUTHOR]

The phase transformation of FeV ($\sigma$ -phase) to Fe2VAl (L21-phase) has been studied by systematic variation of Al concentration in Fe2V2−xAlx ($x = 0-1$). Remarkable changes in magnetic properties were observed with different Al contents. Electrical transport and magnetic properties of these compositions have been investigated in the temperature range, which revealed that the disorder and impurity phase plays an important role in tuning the electronic properties. The observed magnetic anomalies above $\mathrm{T}_{C}$ indicate the heterogeneous magnetic nature of these alloys. The role of Al in electronic transport and the correlation between structural, magnetic, and electrical transport properties are discussed. [ABSTRACT FROM AUTHOR]

We report electronic structure, magnetic properties, and magnetostructural transformations of selected rare earth dialuminides calculated by using local spin density approximation (LSDA), including the Hubbard U parameter (LSDA+U) approach. Total energy calculations show that CeAl2 and EuAl2 adopt antiferromagnetic (AFM) ground states, while dialuminides formed by other magnetic lanthanides have ferromagnetic (FM) ground states. The comparison of theoretical and experimental magnetic moments of CeAl2 indicates that the 4f orbital moment of Ce in CeAl2 is quenched. Theoretical calculations confirm that Eu in EuAl2 and Yb in YbAl2 are divalent. PrAl2 exhibits a tetragonal distortion near FM transition. HoAl2 shows a first order magnetostructural transition while DyAl2 shows a second order transformation below magnetic transition. The dialuminides formed by Nd, Tb, and Er are simple ferromagnets without additional anomalies in the FM state. [ABSTRACT FROM AUTHOR]

The cross responses of the magnetic and electric properties of linarite PbCuSO 4 (OH) 2 to the conjugated electric and magnetic fields are investigated. The theoretical laboratory is built on a frustrated spin chain model of the crystal. A critical phase of metatransitions is strongly highlighted below T N. The sharp magnetic and electric anomalies are attributed to spin-flops. Moreover, the metamagnetic and metaelectric transitions fitting exactly at the same points as the same phenomenon in the magnetoelectric design appear as a signature of the metamagnetoelectric effect. These findings suggest that linarite could be classified as a metamagnetoelectric multiferroic, with promising applications. [Display omitted] • The cross magnetic-electric responses of linarite are investigated. • A critical phase of metatransitions is strongly highlighted below T N. • A clear signature of the metamagnetoelectric effect is recorded. • The results suggest to classify linarite as a metamagnetoelectric multiferroic. [ABSTRACT FROM AUTHOR]