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Sm-Co bulk alloys are well-known permanent magnets having large remanent magnetizations and coercive forces and are widely used in many industrial products. Recently, a large transverse thermoelectric conversion was observed for SmCo5 over a wide temperature range in the absence of magnetic fields. The large thermoelectric conductivity tensors (αxy) was also confirmed by the first-principles density functional theory (DFT) calculations. In this study, we predicted further enhancement of the αxy by including Ni in Co site of SmCo5. We showed that the αxy of Sm(Co1−xNix)5 increases with increasing the Ni ratio and takes the maximum value αxy = 11.3 A K−1 m−1 around x = 0.08 at 300 K, which is about 77% enhancement of αxy = 6.4 A K−1 m−1 in SmCo5. We clarified that the band proximity points near the nodal line of Sm(Co0.92Ni0.08)5 are the main contributing factor to the large Berry curvature, providing the steep slope of the energy dependence in the anomalous Hall conductivity around the Fermi energy. [ABSTRACT FROM AUTHOR]

Sm-Co bulk alloys are well-known permanent magnets having large remanent magnetizations and coercive forces and are widely used in many industrial products. Recently, a large transverse thermoelectric conversion was observed for SmCo5 over a wide temperature range in the absence of magnetic fields. The large thermoelectric conductivity tensors (αxy) was also confirmed by the first-principles density functional theory (DFT) calculations. In this study, we predicted further enhancement of the αxy by including Ni in Co site of SmCo5. We showed that the αxy of Sm(Co1−xNix)5 increases with increasing the Ni ratio and takes the maximum value αxy = 11.3 A K−1 m−1 around x = 0.08 at 300 K, which is about 77% enhancement of αxy = 6.4 A K−1 m−1 in SmCo5. We clarified that the band proximity points near the nodal line of Sm(Co0.92Ni0.08)5 are the main contributing factor to the large Berry curvature, providing the steep slope of the energy dependence in the anomalous Hall conductivity around the Fermi energy. [ABSTRACT FROM AUTHOR]

The ordinary Nernst effect enables large transverse thermoelectric conversion in semimetals, but its operation requires the application of an external magnetic field. In this study, we propose a transverse thermoelectric conversion module structure with embedded permanent magnets and demonstrate thermoelectric power generation by the ordinary Nernst effect in the absence of an external magnetic field. In our prototype module comprising alternately stacked Bi88Sb12 slabs and Nd2Fe14B-type permanent magnets, the stray magnetic field generated by the remanent magnetization of the Nd2Fe14B-type magnets is always applied to the Bi88Sb12 slabs, and a power of 13.2 μW is generated due to the ordinary Nernst effect at a temperature difference of 120 K and average temperature of 260 K at zero external field. This thermoelectric module concept will contribute to the further development of transverse thermoelectric conversion technologies utilizing permanent magnets. [ABSTRACT FROM AUTHOR]

The fabrication of SrFe 12 O 19 ferrite powders with good magnetic properties is a key process in the industrial production of permanent magnets. Remanence and coercivity of the powders was seriously decreased due to the generation of surface lattice defects produced during the crushing of pre-sintered ferrite powders. And the traditionally applied high-temperature annealing above 800 °C can only partially restore the magnetic properties. In this work, the effects of types, adding mode and contents of surfactant (hexadecyl trimethyl ammonium bromide, triethanolamine) on the magnetic properties of crushed powders of the pre-sintered SrFe 12 O 19 ferrite under a low-temperature annealing of 400 °C process were systematically explored. The results showed that surfactants are beneficial to restore or even enhance the magnetic properties of the crushed powders compared with the pre-sintered ferrite due to the refinement of the particles and repairing the surface defects. The surfactant-assisted low-temperature annealing process proposed in this work will promote the commercial production of high performance ferrite powders and ferrite magnets, which can also effectively reduce the production energy consumption. [ABSTRACT FROM AUTHOR]

In order to mitigate the rapid grain growth, a sintered ferrite magnet exhibiting stable characteristics was successfully synthesized. M-type strontium ferrite Sr 1- x Sm x Fe 12- x Co x O 19 (x = 0.00, 0.01, 0.02, 0.03, 0.04, 0.05 and 0.10) was synthesized via a low-temperature co-firing method, incorporating an appropriate quantity of Bi 2 O 3 and CuO as additives within the solid-phase reaction process. The magnetic and electrical properties of the resulting composites were meticulously examined, and X-ray diffraction (XRD) analysis was performed for structural characterization. The findings reveal that a pure hexagonal strontium phase is achieved consistently when the substitution level, x , remains below 0.5. With an increase in the substitution level, a heterogeneous phase α-Fe 2 O 3 becomes apparent within the phase structure. Upon introducing doping elements, the subtle incorporation of SmCo (x ≤ 0.02) enhances the saturation magnetization, remanent magnetization, and coercivity of the composite material. Moreover, the resistances of grain and grain boundary (Rg, Rgb) have been downscaled from 1.856 × 106Ω and 3.61 × 106Ω to 3.182 × 104Ω and 4.37 × 105Ω respectively. Consequently, the Sr 1- x Sm x Fe 12- x Co x O 19 ferrite sintered under low-temperature conditions demonstrates outstanding electromagnetic characteristics, presenting a viable option for materials in microwave device applications. [ABSTRACT FROM AUTHOR]

To better clarify the reliability of redbed paleomagnetic datasets from the Tibetan Plateau and shape of the Qiangtang Terrane (QT) prior to the India-Asia collision, a combined paleomagnetic and detrital zircon U-Pb geochronologic study is conducted on the Upper Cretaceous Abushan Formation (Fm) redbeds, dated to be within 89.1-83.6 Ma, in the Anduo area. The tiltcorrected grand mean direction for 37 sites is Ds = 0.9°, Is = +36.4°, k = 43.6, α95 = 3.6°, which provides a paleopole at 78.2°N, 266.8°E (A95 = 3.6°), corresponding to a paleolatitude of 20.5° ± 3.6°N for the study area (32.3°N, 91.4°E). Reliable demagnetization curves, positive fold, and conglomerate tests support the interpretation that characteristic remanent magnetization directions recorded primary magnetizations carried by detrital hematite and did not suffer from the influence of distortional strains. Our paleomagnetic results indicate that the mean inclination observed from the southwest dipping limb (Is = +44.2°) is clearly steeper than that from the north dipping limb (Is = +34.2°). The results of syntectonic-sedimentation-correction and the fluvial gravel deposits present in the Abushan Fm redbeds sampled support the contention that the apparent inclination discrepancy is attributed to the syntectonic growth strata and that the paleomagnetic datasets observed from two limbs of folds are still reliable. Furthermore, reliable Late Cretaceous paleomagnetic datasets show that the shape of the QT west of the Eastern Himalaya Syntaxis (EHS) during the Late Cretaceous was similar to its present-day relatively E-W alignment, and that around the EHS, its shape changed from the Late Cretaceous NE-SW alignment to the present-day approximately NW-SE alignment. [ABSTRACT FROM AUTHOR]

The magnetic shielding device, made of high-permeability soft magnetic material, is sensitive to external influences and requires a protective steel enclosure. A steel enclosure, being strongly ferrimagnetic, can alter the surrounding magnetic field distribution, thus impacting the shielding effectiveness. This study proposes a novel analytical approach to quantify this effect, which has not been previously researched. The method develops a simplified finite element simulation model based on the structural symmetry of the steel enclosure. By using this model, this study analyzes the impact of steel structures with varying heights, widths, and remanent magnetization values. The validity of the method is confirmed through experimental tests on steel buildings. The findings offer insights into the optimal placement of magnetic shielding systems and provide theoretical guidance for designing large-scale magnetic shielding devices. [ABSTRACT FROM AUTHOR]

Magnetic records from meteorites provide valuable information about the formation and evolution of the solar system and planets. The parent planetesimals of chondrites are typically considered to be undifferentiated based on their primary chemical composition and texture. However, recent paleomagnetic investigations of various chondrites indicate that they carry a primary remanence generated by a dynamo, suggesting partial differentiation of their parent planetesimals. The presence of a dynamo within the parent planetesimal of LL chondrites remains uncertain due to the ambiguous origin of the remanent magnetism. Here, we report petrographic, paleomagnetic, and rock magnetic properties for the novel LL6 chondrite NWA 14180. The high metamorphic temperature experienced by NWA 14180 could have removed the pre‐accretionary remanence. The fusion crust baked‐contact test suggests that NWA 14180 preserves primary magnetic information about its parent body. Alternating field demagnetization results from interior subsamples reveal distinct low‐ and medium‐coercivity components that may represent a viscous remanent magnetization acquired in the geomagnetic field. No natural remanent magnetization was unblocked in the high coercivity range, implying that NWA 14180 cooled in zero‐field conditions. Therefore, we suggest that the parent body of NWA 14180 did not have a dynamo. Furthermore, this result suggests that the LL chondrite parent planetesimal accreted later and was smaller in size than other chondrite classes. Plain Language Summary: Chondrites contain primary material that formed during the first few million years of the solar system. Their parent bodies are believed to have had a concentric structure with gradually increasing metamorphic temperature from surface to center that did not differentiate to form a metallic core. However, several recent paleomagnetic measurements suggest that chondrites may record a stable extraterrestrial remanence attributed to a dynamo magnetic field, indicating that the parent body may be partially differentiated with a convective metallic core inside and unmelted chondritic material on the surface. But whether the LL chondrite parent body featured a dynamo is unknown. Our study shows that a dynamo field did not exist during LL6 chondrite NWA 14180 cooling on its parent planetesimal. Therefore, our results suggest that the LL chondrite parent planetesimal formed later than other chondrite bodies. Key Points: The fine‐grained tetrataenite in NWA 14180 can record paleomagnetic signals if its parent planetesimal has a dynamoPaleomagnetic results for NWA 14180 indicate that it cooled in a zero‐field environment, and no parent planetesimal dynamo existedWe suggest that the LL chondrite parent planetesimal accreted later in the early solar system relative to other chondrites [ABSTRACT FROM AUTHOR]

Using X-ray diffraction (XRD) and a vibrating sample magnetometer (VSM), the effects of Sm substitution, wheel speed, and annealing temperature on the phase formation and magnetic properties of (Y1−xSmx)Co5 (x = 0.2, 0.3, 0.4, 0.5) melt-spun ribbons were investigated. The results indicate the following: (1) With the increase in Sm substitution, it was found that (Y1−xSmx)Co5 ribbons are entirely composed of the (Y-Sm)Co5 phase with a CaCu5-type structure. Additionally, the coercivity gradually increases, while the remanence and saturation magnetization gradually decrease. (2) As the wheel speed increases, the (Y1−xSmx)Co5 ribbons exhibit an increasing proportion of (Y-Sm)Co5 phase until reaching a speed of 40 m/s, where they are entirely composed of the (Y-Sm)Co5 phase. Magnetic measurements show that the coercivity (Hcj) and remanence (Br) of (Y0.5Sm0.5)Co5 ribbons increase gradually with increasing wheel speed, while saturation magnetization decreases. The variation in magnetic properties is mainly attributed to the formation of nucleation centers for reversed magnetic domain (2:7 and 2:17 phases); (3) (Y0.5Sm0.5)Co5 ribbons are composed of the (Y-Sm)Co5 phase and a small amount of the Sm2Co7 phase after annealing at 550 °C, 600 °C, and 650 °C. Temperature elevation promotes crystallization of the amorphous phase, resulting in a gradual decrease in coercivity, while the remanence and saturation magnetization exhibit an overall increasing trend. Through continuous optimization of the process, favorable magnetic properties were achieved under the conditions of a 0.5 Sm substitution level, a wheel speed of 40 m/s, and an annealing temperature of 550 °C, with a coercivity of 7.98 kOe, remanence of 444 kA/m, and saturation magnetization of 508 kA/m. [ABSTRACT FROM AUTHOR]

In this work, the remanence properties and the hyperfine parameters of the strontium hexaferrite were investigated when a copper layer was deposited on its surface using magnetron sputtering. The magnetic properties and maximum energy product were significantly improved after the copper was deposited on the hexaferrite. The magnetic interactions were studied using IRM and DCD remanent magnetization processes and by the construction of the Henkel plots and the δM curves which allowed us to assess the effect of copper on the observed enhancement of the magnetic properties. X-ray diffraction confirms the copper deposition while scanning electron microscopy shows a homogeneous deposited layer. The Mössbauer spectroscopy was used to analyze the effect of copper on the hyperfine parameters of the iron nuclei. Results showed a competition between the magnetizing-like and the demagnetizing-like interactions in the uncoated hexaferrite. However, the strength of the demagnetization-like interaction is significantly weakened because of the copper layer deposited on the hexaferrite surface. This behavior suggests the emergence of a magnetic coupling with a magnetizing effect. In addition, the Mössbauer analysis revealed that copper increased the hyperfine fields and strongly affected the electronic cloud of the 4fI and 2a iron sites. [ABSTRACT FROM AUTHOR]

How and when sedimentary rocks record Earth's magnetic field is complex. Most studies assume a time‐progressive lock‐in mechanism during sediment deposition called depositional remanent magnetization (DRM). However, magnetic minerals can also form in situ, recording a chemical remanent magnetization (CRM) that is discontinuous in time. Disentangling the two mechanisms represents a major hurdle, and differences in their recording efficiencies remain unexplored. Here, our theoretical solutions demonstrate that CRM intensities exceed DRM by a factor of six when acquired in the same magnetic field. Novel experiments growing greigite (Fe3S4) in sediments and subsequent redeposition under identical magnetic field conditions confirm the predicted difference in recording efficiency. Thus, if left unrecognized, CRM leads to overestimated paleointensity and deserves more attention when interpreting Earth's magnetic history from sedimentary records. Recognition of fundamental differences between CRM and DRM characteristics provide a way forward to distinguish the recording mechanisms through routine laboratory protocols. Plain Language Summary: Remanent magnetizations preserved in sedimentary rocks serve as a continuous record of Earth's magnetic field history and play a fundamental role in understanding the Earth system. It is commonly assumed that magnetic minerals align with the magnetic field as a particle settles through the water column, known as a depositional remanent magnetization (DRM). However, diagenesis can lead to chemical growth of magnetic minerals, known as a chemical remanent magnetization (CRM). CRM lacks stratigraphic continuity and can obscure or completely overprint the original magnetization any time after sediment deposition, leading to a magnetic record that is uncorrelated with the age of the rock. Yet, CRMs go largely unrecognized. Theory and experiments in our paper document that CRMs record the magnetic field six times more efficiently than DRMs. Our work provides a way to distinguish the two through routine laboratory protocols. Key Points: Recording efficiency of chemical remanent magnetization (CRM) is six times higher than depositional remanent magnetization (DRM)Undetected chemical remanences lead to overestimated relative paleointensity estimatesComparison of natural and laboratory magnetization and demagnetization behavior help identify chemical remanent magnetizations in sediments [ABSTRACT FROM AUTHOR]

We experimentally investigate magnetization reversal curves for a GeTe topological semimetal. In addition to the known lattice diamagnetic response, we observe narrow magnetization loop in low fields, which should not be expected for non-magnetic material. The diamagnetic hysteresis loop is unusual, so the saturation level is negative in positive fields, and the loop is passed clockwise, in contrast to standard ferromagnetic behavior. We show, that the experimental hysteresis curves cannot be obtained from standard ferromagnetic ones by adding/subtracting of any linear dependence, or even by considering several interacting magnetic phases. The latter possibility is also eliminated by the remanence plots technique (Henkel or plots). We explain our results as a direct consequence of the correlation between ferroelectricity and spin-polarized surface states in GeTe, similarly to magnetoelectric structures. [ABSTRACT FROM AUTHOR]

We provide comparative studies of the structural, morphological, microstructural, and magnetic properties of MnFePSi-glass-coated microwires (MnFePSi-GCMWs) and bulk MnFePSi at different temperatures and magnetic fields. The structure of MnFePSi GCMWs prepared by the Taylor–Ulitovsky method consists of the main Fe2P phase and secondary impurities phases of Mn5Si3 and Fe3Si, as confirmed by XRD analysis. Additionally, a notable reduction in the average grain size from 24 µm for the bulk sample to 36 nm for the glass-coated microwire sample is observed. The analysis of magnetic properties of MnFePSi-glass-coated microwires shows different magnetic behavior as compared to the bulk MnFePSi. High coercivity (450 Oe) and remanence (0.32) are observed for MnFePSi-GCMWs compared to low coercivity and remanent magnetization observed for bulk MnFePSi alloy. In addition, large irreversibility at low temperatures is observed in the thermal dependence of magnetization of microwires. Meanwhile, the bulk sample shows regular ferromagnetic behavior, where the field cooling and field heating magnetic curves show a monotonic increase by decreasing the temperature. The notable separation between field cooling and field heating curves of MnFePSi-GCMWs is seen for the applied field at 1 kOe. Also, the M/M5K vs. T for MNFePSi-GCMWs shows a notable sensitivity at a low magnetic field compared to a very noisy magnetic signal for bulk alloy. The common features for both MnFePSi samples are high Curie temperatures above 400 K. From the experimental results, we can deduce the substantial effect of drawing and quenching involved in the preparation of glass-coated MnFePSi microwires in modification of the microstructure and magnetic properties as compared to the same bulk alloy. The provided studies prove the suitability of the Taylor–Ulitovsky method for the preparation of MnFePSi-glass-coated microwires. [ABSTRACT FROM AUTHOR]

We show the control of the critical current Ic of a superconductor–superconductor/ferromagnet–superconductor [S-(S/F)-S] type switch by the magnetization state of the F. The inverse proximity effect of a S/F bilayer is used to define the weak link and hence the maximum critical current of the junction. The magnetization of the F lead is set by an external magnetic field. We show that the critical current in zero field depends on the remanent magnetization state via stray-field effects and thereby allows for a post-manufacturing control of the junction's properties, in particular the tunability between a maximal critical current and a full suppression of Ic without applying a persistent magnetic field. We propose a simplified model based on the relative orientation of magnetic domains that explains our findings qualitatively. [ABSTRACT FROM AUTHOR]

The Mn0.92Cu0.08‐yZnyFe2O4 (y=0.02, 0.04, 0.06 and 0.08) nanoparticles (MCZF NPs) were synthesized via the hydrothermal process at low operating temperature. The MCZF system generated a cubic spinel structure as seen by the X‐ray diffraction patterns. The average crystallite size was observed to be increasing from 25 to 30 nm. The broad (γ1) and narrow (γ2) absorption bands were seen in FTIR spectra and the cation distributions at tetrahedral (A) and octahedral (B) sites, respectively, was indicated. The surface morphology was analyzed using electron microscopy. Clarification was provided for the dependence of the optical bandgap shift (Eg~1.96–2.15 eV) on the concentration of substituent. The superparamagnetic nature of MCZF can be advantageous for biomedical applications and it was demonstrated by the magnetization versus applied magnetic field (M−H) loops. Small values of remanence magnetization (Mr) and coercivity (Hc) were found using magnetization versus magnetic field (M−H) curves at y=0.02, 0.04, 0.06, and 0.08. This proved that MCZF NPs exhibited the superparamagnetic behavior. The cation distribution at two sublattices was also estimated using a two‐sublattice model. The greatest zone of inhibition in an antibacterial study of MCZF (produced by the green method) was 10.8 mm for Pseudomonosa aeruginosa and 9.4 mm for Staphylococcus aureus. [ABSTRACT FROM AUTHOR]

The spinel ferrites (SFs) are renowned for their distinctive magnetic and electrical characteristics. Sol-gel route was used for the fabrication of Sr0.6 Zn0.4 Gdx Fe2-x O4 (0.00, 0.025, 0.050, 0.075, 0.100) ferrites. The structural, magnetic, microwave, and DC (direct current) properties of prepared Nps were found using of number characterization techniques. The X-ray diffraction (XRD) pattern of Sr0.6 Zn0.4 Gdx Fe2-x O4 SFs showed a single cubic phase. The magnetic behavior was determined by applying a field of 2 kOe. The various magnetic features, including those determined based on the M-H loop, and prepared spinel ferrites showed the soft nature of magnetic materials. When amount of gadolinium (Gd) is increased, then saturation magnetization, coercivity, remanence magnetization is decreased. The Ms values decreased from 69.36 to 32.18 emu/g, coercivity reduced from 220 to 14 emu/g, and remanence magnetization is decreased from 32 to 3 emu/g. The electrical parameters revealed that direct current resistivity and activation energy (Ea) increased (from 0.16 eV to 0.28eV) with the inclusion of the Gd. The activation energy was increased from 0.16 to 0.28 eV. The dielectric constant and loss of permittivity and permeability were determined by applying the frequency 5.5–9.5 GHz. From the above enhanced parameters, it can be concluded that fabricated SFs may be suitable for high-frequency devices. [ABSTRACT FROM AUTHOR]

Magnetofossils are nanosized magnetic fossil remnants of magnetotactic bacteria (MTB) that are widely distributed in marine and freshwater sediments. Past studies have revealed that changes in the morphology and abundance of magnetofossils are linked with diverse paleoenvironmental changes, such as glacial‐interglacial variation, redox conditions associated with primary productivity and organic matter supply, chemical weathering and diagenesis. Besides, it has long been speculated that changes in geomagnetic field intensity could also affect the abundance of magnetofossils. However, it is not yet clear, how these environmental factors controlled past MTB populations in combination. To answer this question, we studied magnetofossils‐rich sediments from cores MD01‐2443 and 2444 off the Southwest Iberian Margin. The paleomagnetic records of our samples reveal geomagnetic excursions corresponding to the Laschamp, Blake, Iceland Basin, and Pringle Falls events. We estimated the relative abundance of magnetofossils in the samples based on isothermal remanent magnetization unmixing and found it to increase during warmer periods and decrease during colder periods, while not covary with changes in the geomagnetic field intensity. To further distinguish the role of different paleoenvironmental factors, we compared magnetofossil abundance with planktonic δ18O, δ13C of organic matter, K/Al and Si/Al, which indicate continental ice volume (paleotemperature), organic matter origin, run‐off intensity and productivity, respectively. The results indicate that less continental ice volume (higher paleotemperature), enhanced productivity and run‐off intensity are closely related and jointly promoted magnetofossil production and preservation. Our study offers a comprehensive approach to understanding how magnetofossil assemblages relate to paleoenvironmental changes off the SW Iberian Margin. Plain Language Summary: Magnetofossils are inorganic remnants of a special kind of bacteria, called magnetotactic bacteria, which live in marine and freshwater sediments and produce tiny magnetic mineral particles for navigation. Previous studies found that magnetofossils can indicate the variation of the environment in the past. However, few studies focus on how magnetofossils vary with the variations in the Earth's magnetic field intensity. In this study, we selected samples of cores MD01‐2443 and 2444 off the Iberian margin to investigate how magnetofossils respond to the environmental change including the variation of geomagnetic field intensity from 18.5 to 49.56 ka and 104.78 to 223.92 ka. We distinguished four geomagnetic excursion events accompanied by a reduction in the geomagnetic field intensity. We applied a new hybrid unmixing method to determine the abundance of magnetofossils in our samples. Our results show that magnetofossil abundance has no relationship with the variation of geomagnetic field intensity. Besides, we used geochemical methods to determine the intensity of river‐off, productivity, and the origin of organic matter off the SW Iberian margin. Our results show that magnetofossils can be controlled by the multiple environmental factors mentioned above. Our study is helpful for better understanding the paleoenvironmental implications of magnetofossils. Key Points: We used a hybrid unmixing approach to quantify the relative abundances of magnetofossils in Quaternary marine sedimentsMagnetofossil abundance correlates with glacial‐interglacial change, productivity, and river run‐off off the SW Iberian marginAn impact of geomagnetic field intensity on magnetofossil content and composition is not apparent [ABSTRACT FROM AUTHOR]

Changes in Earth's magnetic field during the Cretaceous Normal Superchron (CNS) spanning ∼121 Ma to ∼84 Ma hold important clues about the geodynamo evolution. Canonical models predict a persistently strong geomagnetic field with low variability during CNS, which, however, has not been observed in the available absolute paleointensity data and seafloor marine magnetic anomaly (MMA) records. The lack of relative paleointensity (RPI) data across CNS further impedes tests of model predictions. Here, we present a ∼9‐Myr (∼94–∼85 Ma) RPI record from a Turonian to Santonian hemipelagic succession from IODP Site U1512 offshore southern Australia. Detailed paleomagnetic and rock magnetic analyses demonstrate that the ratio of natural remanent magnetization (NRM) demagnetized at 20 mT over magnetic susceptibility (MS), that is, NRM20mT/MS, as a reliable proxy for the RPI of the Upper Cretaceous succession. The new RPI record shows marked changes in both intensity and variability at ∼90.8 Ma. Also, the 6 Myr‐long (∼94–∼88 Ma), near‐continuous, ∼1.2 kyr‐resolution RPI record exhibits a strong positive correlation between field intensity and variability. Assuming this correlation holds for the entire CNS, an extrapolated RPI curve for the entire CNS is obtained by integrating the positive correlation with field variability estimates from the MMA data. The extrapolated RPI curve shows a strong and highly variable field in the middle CNS but a weak and stable field at its beginning and ending. These features imply a much more dynamic geodynamo than previously thought, and provide crucial benchmarks for unraveling the geodynamo evolution during CNS. Plain Language Summary: Cretaceous Normal Superchron (CNS, ∼121 to ∼84 million years ago) marks a nearly 40 million years interval of almost constant normal geomagnetic polarity. Changes in Earth's magnetic field during CNS hold important clues about the evolution of the geodynamo, by which the geomagnetic field was generated. However, whether the geomagnetic field was persistently strong and stable during CNS has been controversial based on estimates from snapshot recordings of igneous rocks and marine magnetic anomaly data. Here, we report a high‐resolution near continuous relative paleointensity (RPI) record of the ∼88–94 million years old interval from a hemipelagic sedimentary succession at IODP Site U1512. The new RPI record documents salient changes in both intensity and variability of the geomagnetic field at ∼90.8 million years ago and a positive correlation between these two parameters toward the ending of CNS. These features imply that the geomagnetic field was strong and highly variable in the middle CNS, but weak and stable at its beginning and ending. These findings indicate much more dynamic geodynamo behavior during the CNS than previously thought, and thus provide important benchmarks for "ground truthing" model simulations to unravel the geodynamo evolution during CNS. Key Points: We report a ∼9 Myr high‐resolution RPI record for the late stage (∼94–∼85 Ma) of CNS from IODP Site U1512 coresThe new RPI record shows a marked change in intensity and variability at ∼90.8 Ma and a positive correlation between these two parametersSalient changes in geomagnetic field's strength and variability imply a much more dynamic geodynamo than previously thought during CNS [ABSTRACT FROM AUTHOR]

The Seiland Igneous Province (SIP) is a large province of mafic and ultramafic (UM) complexes interpreted to be relics of a giant plumbing system feeding the Ediacaran Central Iapetus Magmatic Province. The Reinfjord Ultramafic Complex (RUC) is one of the four major ultramafic complexes of the SIP. The RUC has a younger dunite core surrounded by wehrlite and lherzolite embedded in country rocks consisting of layered gabbros with sub‐horizontal layering and metamorphosed sedimentary rocks. Here, we develop a 3D subsurface model for the RUC using high‐resolution magnetic and gravity data and extensive petrophysical measurements from oriented surface samples and drill core samples. Our model indicates that the RUC narrows in depth, extending a minimum of 1.4 km below sea level, and plunges eastwards below the country rock. This model allows us to decipher the lithologic heterogeneities, and the depth and lateral extent of ultramafic rocks, which we interpret in the context of the geologic history of the area. The RUC is spatially separated from other UM complexes of the SIP and the result of this study indicates a smaller depth extent. Combining these findings with the previously reported distribution of the SIP rocks based on the regional gravity data, we propose that the uplift of the crustal block hosting the RUC is larger than for ultramafic complexes in the northwestern part of the SIP. Plain Language Summary: Worldwide, mafic and ultramafic intrusions are considered potential hosts for economic Ni‐Cu and platinum group elements. Magma‐conduit systems are particularly interesting for such mineralization, because they provide an ideal environment for the formation of large economic sulfide occurrences such as the Norilsk Talnakh deposits. We investigate one of the ultramafic complexes of a large magmatic province considered to represent a deep root zone where transient melts passed en route to upper crustal levels. The RUC is an ideal magma‐conduit system for research of large igneous provinces. Here, we construct a subsurface model of the ultramafic complex using gravity and geomagnetic field data constrained by petrophysical data sets from rock samples. We identified the different mafic and ultramafic units, and the alteration of rocks linked to later tectonic events. The localization and the estimation of relative volumes of altered and unaltered mafic and ultramafic rocks provide information about the geodynamic history and the ore potential of these rocks. Key Points: The modeled structure of the ultramafic complex resulted in a minimum volume of 6.5 km3 and an eastward plunging root with depth of 1.4 kmModeling results suggest localized serpentinization of ultramafic rocks with shallow to negative natural remanent magnetization (NRM) inclination and high Königsberger ratioA new proposed uplift history for the Seiland Igneous Province indicating the southern part as a deeper section of the continental crust [ABSTRACT FROM AUTHOR]

Recovering ancient records of Earth's magnetic field is essential for determining the role of the magnetosphere in protecting early Earth from cosmic radiation and atmospheric escape. We present paleomagnetic field tests hinting that a record of Earth's 3.7‐billion‐year (Ga) old magnetic field may be preserved in the northeastern Isua Supracrustal Belt as a chemical remanent magnetization acquired during amphibolite‐grade metamorphism in the banded iron formation. Multiple petrological and geochronological lines of evidence indicate that the northernmost part of Isua has not experienced metamorphic temperatures exceeding 380°C since the Eoarchean, suggesting the rocks have not been significantly heated since magnetization was acquired. We use "pseudo" baked contact tests (intrusions emplaced 3.26–3.5 Ga ago) and a fold test (folding 3.6 Ga ago) to demonstrate that some samples preserve a ca. 3.7 Ga record of the magnetic field. We recover a field strength of >15 µT. This suggests that Earth's magnetic field may have been weak enough to enhance atmospheric escape during the Archean. Plain Language Summary: Recovering ancient records of Earth's magnetic field is challenging because the magnetization in rocks is often reset by heating during tectonic burial over their long and complex geological histories. We show that rocks from the Isua Supracrustal Belt in West Greenland have experienced three thermal events throughout their geological history. The first event was the most significant, and heated the rocks up to 550°C 3.7‐billion‐years‐ago. The subsequent two events did not heat the rocks in the northernmost part of the area above 380°C. We use multiple lines of evidence to test this claim, including paleomagnetic field tests, the metamorphic mineral assemblages across the area, and the temperatures at which radiometric ages of the observed mineral populations are reset. We use these lines of evidence to argue that an ancient, 3.7 billion year old record of Earth's magnetic field may be preserved in the banded iron formations in the northernmost part of the field area. The magnetization was acquired during mineral transformation associated with the first thermal event and therefore only a lower limit on the strength of the ancient magnetic field was constrained. However, we are able to conclude that the ancient magnetic field was likely comparable with the strength of Earth's magnetic field today. Key Points: The north‐eastern part of the Isua Supracrustal Belt experienced two metamorphic events at 3.69 Ga and 2.85 Ga and one hydrothermal event at 1.5 GaBanded iron formations acquired a chemical remanent magnetization during the first thermal event that was not entirely overprinted by subsequent eventsPaleomagnetic results hint that a record of the Eoarchean geomagnetic field is preserved in the Isua Supracrustal Belt [ABSTRACT FROM AUTHOR]

Paleomagnetic secular variation (PSV) records provide important information for the dynamic processes of the Earth's geomagnetic field, and also can be used for regional stratigraphic correlation. We conducted a paleomagnetic study on a high sedimentation rate Holocene loess section (the Minle section) with precise 14C age constraints in Northwest China. Rock magnetic results indicate that single domain and pseudo‐single‐domain magnetites are the main magnetic carriers of the natural remanent magnetization. Combining the alternating field demagnetization and thermal demagnetization results, we obtained a high‐resolution PSV record with both absolute declination and inclination since ∼13 ka. Combining with previously published sedimentary records in East Asia, we developed an East Asian PSV reference curve over the past 14 ka (EASed14k) by relocating all the data to a common location (30ºN, 108ºE) and averaging them through Fisher statistics. We further generated a regional geomagnetic directional model spanning the past 14 ka for East Asia (SCHA.EAS14k), using the in situ PSV records and applying the revised spherical cap harmonic analysis in space and cubic B‐spline in time. The predicted directional curves from this model at the common location are consistent with the EASed14k curves, which represent the first‐order variation of the geomagnetic field in this area. The established reference curve and regional model for East Asia in this study will be used for regional and global comparison of the geomagnetic field. Plain Language Summary: The geomagnetic field plays an important role in maintaining the Earth's habitability by shielding harmful energetic particles from the universe and serves as a window to the Earth's deep interior. Studying the variation patterns of the geomagnetic field is useful for detecting the geometry of the field, revealing the dynamic process of the Earth as well as stratigraphic correlation and dating. Continuous information of the geomagnetic field can be obtained by performing magnetic measurements on lake, marine and loess sediments. In this study, we conducted paleomagnetic study on a high sedimentation rate Holocene loess section in Northwest China and recovered directional variation of the geomagnetic field since ∼13 ka. And then, we compiled the sediment data and calculated a composite geomagnetic directional reference curve spanning the past ∼14 ka for East Asia. We further established an East Asian regional geomagnetic directional model with the new and compiled data, which can predict variations of the field direction at any point in the region within a spherical cap of 25° centered at 30ºN, 108ºE in East Asia. The established composite curve and regional model in this study provide local reference field for global comparison of the geomagnetic field and space physics study. Key Points: A high‐resolution PSV record includes both absolute declination and inclination since ∼13 ka from a loess section in the Northwest ChinaA composite PSV reference curve over the past 14 ka (EASed14k) based on sediment dataA regional geomagnetic directional model (SCHA.EAS14k) over ∼14 ka was established for East Asia with compiled sediment data in the region [ABSTRACT FROM AUTHOR]

The drift history of the Lhasa terrane plays an essential role in understanding the tectonic evolution of the Bangong-Nujiang Tethyan Ocean and the Neo-Tethyan Ocean, as well as the evolutionary history of the Tibetan Plateau. Here, a combined rock magnetic, petrographic, and palaeomagnetic study is performed on the Upper Permian–Lower Triassic limestones (∼259–251 Ma) in the western Lhasa terrane. The site-mean direction for the 28 sites is D g = 32.1°, I g = 50.3°, k g = 47.9 and α 95 = 4.0° in situ and D s = 342.9°, I s = 32.7°, k s = 43.2 and α 95 = 4.2° after tilt-correction, yielding a palaeopole at 68.9°N, 314.4°E with A 95 = 4.3°, corresponding to a palaeolatitude of 18.0° ± 4.3°N. The fold tests are not significant because the sampling section shows monoclinic features with minor variations in their bedding attitudes. The palaeopoles for the directions before and after tilt-correction are compared with reliable Late Permian–Palaeogene palaeopoles obtained from the Lhasa terrane. Based on these comparisons, the studied limestones were remagnetized prior to tilting and this remagnetization most likely occurred during the Early Cretaceous. The depositional environment of the limestones may have changed from anoxic to suboxic and oxic during the Early Cretaceous, leading to the oxidation of iron sulphide to authigenic magnetite. Meanwhile, the Late Jurassic–Early Cretaceous convergence between the western Lhasa and Qiangtang terranes may have resulted in tectonic fluid migration and the formation of calcite veins and stylolites in the limestones. This is supported by the presence of small calcite veins and stylolites in some samples, as well as the fact that the framboidal oxides were formerly sulphides (mostly pyrite), implying that the majority of the iron oxides observed in the limestones were authigenic. These processes indicate that chemical remanent magnetization caused by the growth of magnetic minerals related to tectonic fluid migration was most likely the mechanism for the limestone remagnetization. [ABSTRACT FROM AUTHOR]

Airborne magnetic particles may be harmful because of their composition, morphology, and association with potentially toxic elements that may be observed through relationships between magnetic parameters and pollution indices, such as the Tomlinson pollution load index (PLI). We present a fuzzy-based analysis of magnetic biomonitoring data from four Latin American cities, which allows us to construct a magnetic index of contamination (IMC). This IMC uses four magnetic parameters, i.e., magnetic susceptibility χ, saturation isothermal remanent magnetization SIRM, coercivity of remanence Hcr, and SIRM/χ, and proposes summarizing the information to assess an area based exclusively on magnetic parameters more easily. The fuzzy inference system membership functions are built from the standardization of the data to become independent of the values. The proposed IMC is calculated using the baseline values for each case study, similar to the PLI. The highest IMC values were obtained in sites close to industrial areas, and in contrast, the lowest ones were observed in residential areas far from avenues or highways. The linear regression model between modeled IMC and PLI data yielded robust correlations of R2 > 0.85. The IMC is proposed as a complementary tool for air particle pollution and is a cost-effective magnetic approach for monitoring areas. [ABSTRACT FROM AUTHOR]

Mineral exploration projects can make considerable use of a variety of geophysical techniques and datasets, including magnetic and gravity data. The interpretation of large quantities of data can be very time consuming, so semi-automatic interpretation techniques are often used to provide initial estimates of the parameters (primarily the location and depth) of the sources of anomalies. Euler deconvolution is a commonly used interpretation method for potential fields which has a number of advantages over many other techniques, such as working in the presence of remanent magnetisation, and not being restricted to a particular model such as a contact. A second-order version of Euler's equation is introduced here, which is much less affected by trends in the data than the standard method and additionally produces depth parabolas, which simplify the interpretation of results. The method was applied to aeromagnetic data from a mineral exploration project in Southern Africa and provided plausible results. [ABSTRACT FROM AUTHOR]

Micromagnets integrated into microelectromechanical systems devices are widely used in the fields of micro-energy harvesters, micro-actuators, and speakers. A novel method for fabricating NdFeB micromagnets based on vacuum negative pressure injection is presented. The influence of array element shape, size, and injection channel on the surface magnetic field was studied by Maxwell finite element analysis. A circle array of 600 µm diameter and 150 µm spacing could generate a stronger magnetic field at the edge of the magnet array. Micron-sized magnetic powders with a diameter of 5 µm mixed with the SU8 T2010 photoresist were filled into the microcavity on a PDMS (polydimethylsiloxane) elastomer, which was prepared by the SU8 positive membrane. The PDMS elastomer was bonded to the glass substrate and degassed by a vacuum pump to form negative pressure for rapid injection and uniform filling. By selecting a suitable binder and optimizing the mixing ratio of the magnetic powder, a 165 µm thick micromagnet with homogeneous dispersion of magnetic powder particles was achieved, and the weight percentage of magnetic powder in the SU8 photoresist was 41.8%. The remanent magnetization of micromagnets was 42 emu/g, the coercivity was 6895 Oe, and the maximum surface magnetic field strength was 1.3 mT after magnetization in a 2 T uniform magnetic field. Finally, the micromagnet array was utilized in a cantilever beam micro-actuator, which could drive the cantilever beam and exhibit an excellent linearity. [ABSTRACT FROM AUTHOR]

Optimizing the spinodal decomposition structure in Alnico magnets is a very effective way to improve the performance. Some elemental additives are extremely sensitive to the spinodal decomposition process. In this manuscript, the evolution of spinodal decomposition structure in isotropic Alnico 8 ribbons with various Ti contents and its effects on magnetic properties and service performance are investigated. Alnico 8 ribbons with nominal composition of different Ti content (3.5 wt%-7.5 wt%) were prepared by melt-spinning and simplified heat treatment. The optimum magnetic properties of the ribbons such as intrinsic coercivity, Hcj=860 Oe, remanence magnetization, Br =5.89 kGs, and maximum magnetic energy product, (BH)max=1.2 MGOe are obtained for 5.5 wt% Ti. The ribbons show excellent temperature stability, their magnetic properties are 100% reversible up to 800 K and can be maintained above 85% at 800 K. The increase of Ti decreases the Curie temperature of the ribbons slightly. The evolution of spinodal decomposition phases and its influence mechanisms on magnetic properties are studied. [ABSTRACT FROM AUTHOR]

The exchange integral in the magnetic response of a spherical metallic iron (Fe) and nickel (Ni) nanoparticle is theoretically studied by using Monte Carlo simulations. To this end, using the nanoparticles model in spherical coordinates, we compute magnetization, magnetic susceptibility, specific heat, internal energy, and hysteresis loop over a wide range of temperatures for an Fe and Ni nanoparticle with a size of about 2 nm. The phase transition temperatures are interpolated versus the exchange parameters, and it is observed that the dependence on the coupling parameter is completely linear. Moreover, from the susceptibility results of the samples, the sharpest peak with the least fluctuation gives us the most appropriate Curie temperature and exchange integral for this system. However, the peak related to the heat capacity is also in the Curie temperature range. From the internal energy results, it can be understood that with the increase in phase transition and interaction, the system reaches equilibrium. The magnetic coercive field and remanent magnetization caused by nanoparticles indicate superparamagnetic properties at room temperature. At the end, the obtained results allow us to theoretically determine the magnetic properties of spherical nanoparticles and pave the way for the development of nanoparticles for many applications. [ABSTRACT FROM AUTHOR]

Developing advanced magnetorheological elastomers (MREs) with a range of specific characteristics is essential for matching the growing demands from a wide spectrum of applications such as automotive, healthcare, sensors, and actuators. However, the compatibility problems between constituents and the low magnetorheological (MR) effect have limited their performance and integration into actual applications. Here, a novel MRE consisting of styrene-b-(ethylene-co-butylene)-b-styrene (SEBS) and Ni-rich Permalloy (Ni80Fe17Mo3) has been developed with remarkable functional properties. The correlation between the filler concentration and microstructural, mechanical, thermal, magnetic, and MR properties is reported. The incorporation of Ni-rich Permalloy has a reinforcement effect in the polymer matrix and leads to an improvement of the thermal stability. Further, the saturation magnetization and remanence of the composites increase with increasing filler content. In particular, the saturation magnetization increases from 14.3 to 41.9 A m&#178/kg, and the remanence from 1.2 to 4.0 A m²/kg when the concentration increases from 20 to 60 wt%. Finally, the MR effect of composites with 20, 40, and 60 wt% filler content is 8%, 15%, and 35%, respectively. A magnetic dipole interaction model is used to discuss the MR effect and a relation between the MR effect and the main parameters affecting it is proposed. Importantly, the obtained MR values are higher when compared with related composites for the same magnetic content, and for the same or similar polymeric matrices, demonstrating the suitability of the developed materials for the fabrication of high-response functional MR devices. [ABSTRACT FROM AUTHOR]

This paper proposes an array structure with multidirectional remanent magnetization based on hard-magnetic soft materials, which can be used as a soft switch array on planar and curved surfaces. We firstly investigate the displacement response of a hard-magnetic soft switch which is excited by a magnetic field, and related to the magnitude and direction of the magnetic field. When the remanent magnetization direction of the soft switch is opposite to the horizontal component of the magnetic field, the displacement response is greater than that of the driving magnetic field in other directions. The maximum displacement of the soft switch can reach 4.5 mm under a 6 V driving voltage applied to the Helmholtz coil. We further design 2 × 2 and 3 × 3 switch arrays and the circuit structures of the switch arrays. The switch arrays are fabricated, and the displacement responses of the switch arrays under different driving magnetic fields on planar and curved surfaces are finally demonstrated. When the Z-axis displacement of the device reaches more than 3 mm, the LED light can be switched on. The hard-magnetic soft switch array structure designed in this paper can enable the application of soft switches in curved environments, verifying the feasibility of the application of hardmagnetic soft switch arrays. It is expected to provide a guidance for the design and manufacturing of multi-functional hard-magnetic soft switches in the future and the application of hard-magnetic soft switch arrays in planar and curved environments. [ABSTRACT FROM AUTHOR]

In this study, our aim was to synthesize Gd–Ni doped M-type calcium hexaferrites using a solid-state reaction method. The chemical composition of the synthesized material was Ca1−xGdxFe12−yNiyO19, (0.00 ≤ x, y ≤ 0.07). This study focused on examining the impact of low concentrations of Gd3+ and Ni2+ ions in the formula. The M-type hexagonal structure was confirmed with high certainty using powder X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, and Raman spectroscopy. In addition, a minor impurity phase, α-Fe2O3, was detected. Field-emission scanning electron microscopy (FESEM) analysis focused on examining the surface morphology of the sample, and the obtained images revealed the presence of anticipated grain sizes ranging from 0.80 to 1.06 μm. This study employed energy-dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS) to validate the elemental composition and oxidation states of the constituent elements. A vibrating sample magnetometer (VSM) and theoretical calculations are used to determine crucial parameters, including remanent magnetization (Mr), coercivity (Hc), saturation magnetization (Ms), squareness ratio (Mr/Ms ≤ 0.5), magneton number (μB), and magneto-crystalline anisotropy constant (Ka). Examination of these parameters contributes to a deeper understanding of the magnetic properties under investigation. This paper presents an analysis of the obtained samples, highlighting their remarkable suitability for applications in high-frequency devices and high-density recording media. [ABSTRACT FROM AUTHOR]

The phase evolution, magnetic properties and microstructure of rod-shaped permanent magnets prepared by annealing the amorphous precursor Fe70−xNd7B21Zr2Nbx (x = 0–3.0) were systematically studied. X-ray diffraction analysis, magnetometer, microstructure and δM-plots studies show that the good magnetic properties of the magnet are attributed to the uniform microstructure composed of exchange-coupled α-Fe and Nd2Fe14B phases. Nb addition to Fe67.5Nd7B21Zr2Nb2.5 alloy led to an increase in the volume fraction of the soft magnetic phase, reinforced exchange coupling and improved magnetic properties. The magnetic properties of the optimized annealed Fe67.5Nd7B21Zr2Nb2.5 rod are: coercivity (Hci) = 513.92 kA/m, remanence (Br) = 0.58 T, squareness (Hk/Hci) = 0.24 and magnetic energy product ((BH)max) = 37.59 kJ/m3. [ABSTRACT FROM AUTHOR]

The citrate approach was employed to successfully synthesize Mn0.4Zn0.6−xCuxFe2O4 (MZCF) with a nanostructured shape. A thorough examination was conducted on the microstructural, magnetic, and optical properties of the nanoparticles obtained. The X-ray diffraction (XRD) patterns revealed that all of the compositions exhibit a high degree of single-phase spinel formation. The experimental findings indicate that the introduction of copper ions leads to a reduction in both lattice constant and porosity, while concurrently resulting in an increase in the theoretical X-ray and bulk densities. The analysis of UV–Vis spectroscopy indicated that MZCF exhibited a direct band gap falling within the range of 1.61–1.78 eV. The magnetic characteristics were assessed through the analysis of hysteresis plots. The introduction of copper (Cu) content leads to notable improvements in the saturation (Ms) and remanent magnetization (Mr) values, which range from 40.21 to 58.78 and 4.46–10.54 emu/g, respectively. The assessment of the microwave frequency response has verified the appropriateness of MZCF nanoferrites for application within the frequency spectrum spanning from 8 to 13 gigahertz. The nanoparticles exhibit improved magnetic properties, suggesting their potential appropriateness for applications involving high-frequency microwave absorption and switching. Furthermore, the nanoparticles Mn0.4Zn0.6Fe2O4 and Mn0.4Zn0.2Cu0.4Fe2O4 were subjected to analysis utilizing a solar light simulator in order to induce degradation of MB dye. [ABSTRACT FROM AUTHOR]

Coercivity and magnetic viscosity studies are presented in coprecipitated and ceramic BaFe12O19 hexaferrites. According to magnetic viscosity formalism, the activation volumes are obtained and for ceramic sample the temperature dependence of the activation volume is reported. Using remanence curves, interactions are evaluated by means of the ΔM technique. In both samples, interactions are evidenced, particularly demagnetizing‐like interactions. The activation volume values seem to indicate that coherent rotation is not the mechanism of magnetization reversal even in the sample with particle size below the critical single‐domain size. It is confirmed that the activation volume increases with temperature in 75–300 K temperature range, for both coprecipitated and ceramic samples. [ABSTRACT FROM AUTHOR]

LaFeO3 perovskite oxide were synthesized through solution combustion technique using ascorbic acid as phytochemical fuel. The sample was characterized using techniques such as XRD, FTIR, UV-Visible spectroscopy, SEM with EDX and XPS. The magnetic hysteresis behavior was studied using VSM measurement at room temperature. The orthorhombic primitive lattices of LaFeO3 under the space group Pnma was confirmed from XRD pattern and the lattice parameters were obtained using Rietveld profile refinement. The crystallographic structure and lattice parameters were found consistent with the data presented in the ICDD PCPDFWIN Number 37-1493 file. Using Scherrer equation the average crystallite size (26 nm) was estimated. The strain separated effective crystallite size (35 nm) was estimated using the model suggested by Williamson–Hall. The M–O bond vibration bands correspond to LaFeO3 crystal lattice were elucidated from FTIR spectrum. Using the raw reflectance data from UV-Visible spectrum, Tauc' plot analysis employing Kubelka Munk function was performed; from which the optical direct band gap (2.41 eV) was estimated. The particle size distribution and elemental composition were estimated from SEM with EDX. The binding energies obtained from deconvoluted XPS spectra accurately provide the valence state electronic configuration corresponding to La and Fe atoms in the prepared LaFeO3 sample. The weak ferromagnetic relaxation with finite coercivity (0.18248 kOe) and remanent magnetization (0.2825 emu. g−1) was estimated from M–H curve analysis using VSM data at room temperature. [ABSTRACT FROM AUTHOR]

Microwave combustion method (MCM) was utilized to synthesize nanoparticles of Mn- Mn doped CuFe2O4 (Mn: CuFe2O4). The crystallite size ranged from 19 to 22 nm, determined from the XRD studies of Mn: CuFe2O4 nanoparticles employing the Debye Scherrer formula. X-ray photoelectron spectroscopy (XPS) analysis was employed to determine the chemical elements and their respective oxidation states. The agglomerative nanoparticles exhibited a spherical shape as observed through HR-SEM. The elemental composition of the nanoparticles was determined through EDX analysis, which indicated the presence of Mn, Cu, Fe, and O. The sample completely analyzed by TEM SAED, EPR and BET. The samples produced were analyzed using diffuse reflectance spectroscopy, which revealed energy gap values ranging from 2.10 to 2.30 eV. The observed photoluminescence emissions in the visible range of 415–450 nm in all samples suggest the presence of oxygen vacancies. Magnetic properties viz. remanent magnetization, coercivity, and saturation magnetization deduced from the hysteresis curves (B-H). Further nanoparticles that were synthesized were subjected to photocatalytic degradation (PCD) of rhodamine B under visible light. The spinel system of CuFe2O4 exhibits reactivity towards H2O2, leading to a process akin to the Fenton reaction. The chemical components of RhB dye confirmed by Total ion chromatography. The photocatalytic performance of the CMF5 sample is superior when compared to the other samples. The possible mechanisms amenable to the PCD method are elaborated. [ABSTRACT FROM AUTHOR]

We demonstrate a simple and compact variable magnetic field source based on the permanent cube magnet array approximating a Halbach cylinder. The large air gap area accommodates standard cryostat tails while providing a high uniformity and magnetic field stability of up to 0.5 T over regions of up to about a centimeter. It eliminates magnetic remanence effects and produces reproducible fields without the need for feedback. Thanks to the low cost and exceptional energy efficiency, it provides an accessible solution for modest magnetic field requirements in a wide range of research applications. [ABSTRACT FROM AUTHOR]

By pressure demagnetization, take iron as an example, we mean either that, given an external magnetic field under a certain temperature, the magnetization becomes weaker as the pressure increases, which can be referred to as pressure demagnetization during magnetization, or that when external field is dropped to zero, the iron has residual magnetization or remanence, and the residual magnetization becomes weaker as the pressure increases as well, which can be referred to as pressure demagnetization in remanence. In order to account for the pressure demagnetization, we demonstrate that, though magnetic work has two equivalent forms in electromagnetism, only one form is proper in thermodynamics in general. [ABSTRACT FROM AUTHOR]

The present study reports the effect of niobium substitution on structural and magnetic properties of CoNbyFe2-yO4 (0.00 ≤ y ≤ 0.08) nanomaterials. XRD studies confirm the formation of pure cubic spinel phase with nanocrystalline nature of CoNbyFe2-yO4. The values of lattice parameters (a) decrease with Nb content (y) for CoNbyFe2-yO4, i.e. from a = 8.3656 Å to 8.3629 Å for y = 0.00 to y = 0.08, respectively. Crystallite sizes decrease with the increase of 'y' for CoNbyFe2-yO4, i.e. from 29 nm (y = 0.00) to 19 nm (y = 0.08). FTIR studies confirm the presence of two distinct IR bands in the range of 584 cm−1 – 590 cm−1 and 408 cm−1 – 410 cm−1 for stretching vibrations corresponding to the M–O bonds at tetrahedral and octahedral sites, respectively. FESEM micrographs illustrate the spherical morphology of CoNbyFe2-yO4. The values of saturation magnetization (Ms), coercivity (Hc) and remanent magnetization (Mr) were obtained from VSM measurements. The decrease in Ms was observed from 76.2 emu/g (y = 0.00) to 66.9 emu/g (y = 0.08) as a result of increase in 'y'. The significant deviation in the Hc was observed from 1525 to 806 Oe for y = 0.00 to y = 0.08, respectively. All compositions of CoNbyFe2-yO4 show squareness ratio (Mr/Ms) values in the range of 0.4542–0.3214. The variation of magnetic parameters (Ms, Hc, Mr/Ms) for CoNbyFe2-yO4 nanomaterials are best explained on the basis of varying Nb atom substitution leading to cation distributions and possible surface spin disorder due to size and surface effects. [ABSTRACT FROM AUTHOR]

Remanent magnetization of Y0.5Lu0.5Ba2Cu3Oy superconductor produced by a modified melt powder melt growth (MPMG) technique at 25 K temperature has been investigated by both experimental and numerical computations using H-formulation in the finite element method (FEM). At the low field and low-temperature conditions, remanent magnetization MREM is equal to the difference between the field cooled magnetization MFC and zero field cooled magnetization MZFC. Experimental data for remanent magnetization as a function of temperature can be reproduced quite well by numerical computations based on H-formulation providing an estimation of how the critical current density varies with temperature. The critical current density at 25 K was estimated to be a 6.50 × 108 A/m2, and the temperature dependence is determined as (1 − T/Tc)2.5 from the best fit curve of MREM(T) for the sample studied. In numerical calculations, we have used Jc(H) = Jc0/(1 + H/HREF), where HREF is a constant characterizing the superconducting sample. Furthermore, both flux density profile and current density profile have been obtained from the numerical calculations for various stages of the field applications or temperature values during the heating process. [ABSTRACT FROM AUTHOR]

We present the first rock magnetic and paleomagnetic analyses of the Martian meteorite Grove Mountains (GRV) 020090, a suitable candidate for paleomagnetic study due to its low degree of weathering and shock metamorphism. Petrological and rock magnetic investigation indicates that pyrrhotite is the dominant magnetic mineral in GRV 020090, where it occurs as a primary phase without significant shock metamorphism or alteration. The magnetic grains in GRV 020090 exhibit single‐domain behavior that facilitates high‐fidelity magnetic recording. We obtained a positive fusion‐crust baked contact test, which supports an extraterrestrial origin of the primary remanence in GRV 020090. The nature of the primary remanence was identified as thermoremanence acquired during crystallization of the rock on Mars. Anhysteretic remanent magnetization and isothermal remanent magnetization paleointensity methods indicated paleofield strengths of 1.6 and 2.6 μT, respectively, for the primary remanence. However, the shock pressure that GRV 020090 experienced may have partially demagnetized the primary remanence, leading to underestimated paleointensity values. Therefore, 1.6 μT is regarded as the lower limit on the paleointensity of GRV 020090. This lower limit is higher than the model‐predicted surface magnetic field strength in the source region for GRV 020090, suggesting that it may have recorded a small‐scale crustal magnetic field previously undetected by orbital magnetic data. This small‐scale crustal field is likely generated by the underlying ancient, magnetized layers, as the crustal magnetization of the surficial terrane with lithology similar to GRV 020090 is too weak to produce such a crustal field. [ABSTRACT FROM AUTHOR]

Knowledge of the shock remanent magnetization (SRM) property is crucial for interpreting the spatial change in a magnetic anomaly observed over an impact crater. This study conducted two series of impact‐induced SRM acquisition experiments by varying the applied field intensity (0–400 μT) and impact conditions. Systematic remanence measurements of cube‐shaped subsamples cut from shocked basalt containing single‐domain titanomagnetite were conducted to investigate the effects of changes in pressure and temperature on the SRM acquisition. The peak pressure and temperature distributions in the shocked samples were estimated using shock‐physics modeling. SRM intensity was proportional to the applied field intensity of up to 400 μT. SRM intensity data for peak pressure and temperature of up to 8.0 GPa and 530 K, respectively, clearly show that it increases with increasing pressure and decreases with increasing temperature. The SRM has unblocking temperature components up to a Curie temperature of 510 K, and it easily demagnetizes with alternating field demagnetization. The observed SRM properties can be explained by the pressure‐induced microcoercivity reduction and temperature‐induced modification of the blocking curve. Although the remanence acquisition efficiency of the SRM is significantly lower than that of the thermoremanent magnetization (TRM), the magnetic anomaly originating from the SRM distribution in a broader region may show a contribution comparable to that of the impact‐induced TRM distribution in a narrow region. Plain Language Summary: Crustal rocks on terrestrial planets acquire remanent magnetization at the time of an impact event as shock remanence. Magnetic field data observed over impact craters play a key role in reconstructing the magnetic field histories of terrestrial planets. Knowledge of shock remanence is crucial for interpreting the spatial changes in the magnetic field observed over an impact crater. In this study, a suite of shock remanence acquisition and evaluation experiments were conducted to investigate the effects of pressure and temperature changes during shock wave propagation on shock remanence acquisition. The experimentally observed characteristics of shock remanence, such as the stability with respect to thermal and alternating field demagnetization and the systematic intensity changes with respect to pressure and temperature changes, are qualitatively explained by the pressure‐ and temperature‐induced changes in magnetic properties during shock wave propagation. The shock remanence intensity with respect to impact conditions was evaluated using newly obtained experimental data, which enabled us to quantitatively evaluate the shock remanence distributions and their contribution to the magnetic field over impact craters. The shock remanence contribution is estimated to be comparable to that of the impact‐induced thermoremanent magnetization, considering the intensity and volume of these remanences. Key Points: Shock remanence acquisition and evaluation experiments are conducted to evaluate the effects of pressure and temperature changesCharacteristics of shock remanence can be explained by a pressure‐induced microcoercivity reduction and a temperature effect on itContribution of shock remanence to magnetic anomaly over crater is estimated to be comparable with that of impact‐induced thermoremanence [ABSTRACT FROM AUTHOR]

The Mn-Zn ferrite with a composition of Mn0.25Mg0.08Cu0.25Zn0.42Fe2O4 has been synthesized in this study using the chemical sol-gel technique at a pH of 7. The sample was prepared and subsequently annealed at a temperature of 700°C. The nanocrystalline ferrite samples were subjected to characterization using X-ray diffraction (XRD), Fourier transform-infrared spectroscopy (FT-IR), Scanning electron microscopy (SEM), Thermogravimetry (TG), and Differential thermal analysis (DTA). The findings of these observations are delineated and deliberated. The sample's phase composition was verified using X-ray diffraction examination. The crystalline size was determined using Scherrer's formula and was observed to be within the range of 20-75 nm. Two notable stretching bands were seen in the FTIR spectra within the range of 400-650 cm-1. The spinel structure of the produced nanoparticles was confirmed by these two bands. The magnetic characteristics of the powder were examined using a Vibrating Sample Magnetometer (VSM). The presence of M-H hysteresis loops suggests that the produced nanoparticles have superparamagnetic properties, as evidenced by their low coercive force, remanent magnetization, and saturation magnetization values. [ABSTRACT FROM AUTHOR]

Coercivity and magnetic viscosity studies are presented in coprecipitated and ceramic BaFe12O19 hexaferrites. According to magnetic viscosity formalism, the activation volumes are obtained and for ceramic sample the temperature dependence of the activation volume is reported. Using remanence curves, interactions are evaluated by means of the ΔM technique. In both samples, interactions are evidenced, particularly demagnetizing‐like interactions. The activation volume values seem to indicate that coherent rotation is not the mechanism of magnetization reversal even in the sample with particle size below the critical single‐domain size. It is confirmed that the activation volume increases with temperature in 75–300 K temperature range, for both coprecipitated and ceramic samples. [ABSTRACT FROM AUTHOR]

The study of europium-substituted Cu-Zn spinel ferrites (Cu0.6Zn0.4EuxFe2−xO4) is important for high-frequency applications as they can have a substantial effect on the magnetic and electrical residences of these materials. Single-phase nano-structured ferrites with varying amounts of Eu were synthesized using the sol–gel technique. The crystalline characteristics were identified using x-ray diffraction (XRD) testing, which demonstrated a rise in lattice parameters as the Eu concentration increased. The DC (direct current) resistivity measurements showed that the samples exhibit a semiconducting behavior, with a decrease in resistance at elevated temperatures. We found that the measured magnetic properties of magnetic saturation (Ms), remanence magnetization (Mr), and coercivity (Hc) were all impacted by the presence of Eu substitution. The saturation magnetization and remanence magnetization decreased while the coercivity increased, making the Eu-doped Cu-Zn spinel ferrites efficient magnetic semiconductors. The improved magnetic and electrical properties make these materials suitable for high-frequency applications. [ABSTRACT FROM AUTHOR]

In order to study the impact of human activities on urban soil environment, the soil profile of a plot of dry-land dug at the foot of the Zhuizi Mountain (117.46°E, 32.91°N) in Bengbu City was investigated to examine its property regarding the content of mineral components and heavy metal elements (Zn, Pb, Cr, Ni, Cu); additionally, its magnetic parameters were measured including low-frequency volume magnetic susceptibility (KL), high-frequency volume magnetic susceptibility (KH), anhysteretic remanent magnetization (ARM), isothermal remanent magnetization (IRM, SIRM), temperature-dependent magnetic susceptibilities (k-T curve), and the measured data were calculated and statistically analyzed. The findings of the study reveals that the soil profile mainly consists of minerals such as quartz, albite, potassium feldspar, illite and montmorillonite; owing to the influence of human activities in the City, the content of Zn and Pb in the top soil was significantly increased; magnetic minerals in the soil includes magnetite hematite, goethite and lepidocrocite, but was relatively low, the magnetic properties of the soil profile are mainly dominated by ferrimagnetic minerals. According to the variation of magnetic parameters related with depth of the soil profile, the soil profile can be divided into two layers: 0-20 cm being the first layer, 20-80 cm the second layer. The magnetic property of the second layer of soil is mainly determined by the soil parent material, on the other hand, the first layer of soil has been affected by strong magnetic particles brought about by urban human activities, the average values of x, SIRM and XARM being remarkably higher than those of the second layer, while Xfd and XARM/SIRM average values lower than those of the second layer, reflecting an increase in the content of magnetic mineral and coarsening of particles in the first layer of soil. The facts of magnetic parameter values vary with depth of the soil profile within 0-20 cm reflected the process and degree of influence on the dry-land soil profile, exerted by urban human activities. [ABSTRACT FROM AUTHOR]

We investigate the effect of an applied magnetic field on the entire HDDR process using a customized reactor vessel and a warm-bore superconducting magnet. We analyzed the resulting properties produced at both a 0 applied field and a 2 Tesla applied field. We show that the application of a magnetic field throughout the HDDR process results in powders that exhibit a greater level of anisotropy compared to their ambient field counterparts. [ABSTRACT FROM AUTHOR]

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