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Near-zero magnetic shielding systems (MSSs) can provide basic experimental environments for extremely weak magnetic measurements. Reducing the internal magnetic field of MSS is the crucial element of high-sensitivity measurements, which is related to the shielding material flux. As an effective way to regulate the material remanence, degaussing reconstructs the magnetic balance with the geomagnetic field. However, previous research studies mainly focused on the optimization of material degaussing, with few considering the practical application scenarios of MSS. In this work, a numerical modeling method is proposed to realistically depict the balancing process, and the mapping relationship between the internal magnetic field of the MSS and the degaussing current is established. First, the magnetic field source analysis is carried out, and the internal magnetic field fluctuations of the MSS during degaussing are decomposed into multi-harmonic components. Then, the phase and amplitude changes of the hysteresis loop are simulated to predict the residual field. Thereafter, the effectiveness of the method is verified by a magnetic shielding cylinder. The experimental results indicate that the slight difference in material remanence has a negligible effect on the residual field. This work has potential application value in the research of degaussing technology. [ABSTRACT FROM AUTHOR]

Tailoring the crystal structure, spin, and charge state of perovskite oxides through fluorine ion doping is an attractive and effective strategy, which could significantly modify the physical and chemical properties of base oxides. Here, BaFe1−xMnxO3−δ (x = 0, 0.1, 0.2, 0.3) and BaFe1−xMnxO2.9−δF0.1 (x = 0.1, 0.2, 0.3), belonging to 6H-type BaFeO3−δ, are prepared and investigated to evaluate the impact of F− doping. The distortion of crystal structure and the reduced average valence of Mn and Fe confirm the preference for F− substitution in the hexagonal layer, which are found as the key factors for the improved magnetic properties, including ferromagnetic ordering temperature, coercive force, and remanent magnetization. Moreover, the valence reduction of B-site ions and the increased resistance distinctly indicate the expense of electron hole via fluorine doping. This work describes the adjustment of crystal structure, electronic configuration, and ferromagnetic performance by simple F− doping, which provides a prospect for practical magnetic materials. [ABSTRACT FROM AUTHOR]

Tailoring the crystal structure, spin, and charge state of perovskite oxides through fluorine ion doping is an attractive and effective strategy, which could significantly modify the physical and chemical properties of base oxides. Here, BaFe1−xMnxO3−δ (x = 0, 0.1, 0.2, 0.3) and BaFe1−xMnxO2.9−δF0.1 (x = 0.1, 0.2, 0.3), belonging to 6H-type BaFeO3−δ, are prepared and investigated to evaluate the impact of F− doping. The distortion of crystal structure and the reduced average valence of Mn and Fe confirm the preference for F− substitution in the hexagonal layer, which are found as the key factors for the improved magnetic properties, including ferromagnetic ordering temperature, coercive force, and remanent magnetization. Moreover, the valence reduction of B-site ions and the increased resistance distinctly indicate the expense of electron hole via fluorine doping. This work describes the adjustment of crystal structure, electronic configuration, and ferromagnetic performance by simple F− doping, which provides a prospect for practical magnetic materials. [ABSTRACT FROM AUTHOR]

The phenomenon of exchange bias has been extensively studied within crystalline materials, encompassing a broad spectrum from nanoparticles to thin-film systems. Nonetheless, exchange bias in amorphous alloys has remained a relatively unexplored domain, primarily owing to their inherently uniform disordered atomic structure and lacking grain boundaries. In this study, we present a unique instance of exchange bias observed in Fe–B–Nb amorphous thin films, offering insights into its origins intertwined with the system's spin-glass-like behavior at lower temperatures. The quantification of exchange bias was accomplished through a meticulous analysis of magnetic reversal behaviors in the liquid-helium temperature range, employing a zero-field cooling approach from various initial remanent magnetization states (±MR). At reduced temperatures, the appearance of asymmetric hysteresis, a hallmark of negative exchange bias, undergoes a transformation into symmetric hysteresis loops at elevated temperatures, underscoring the intimate connection between exchange-bias and dynamic magnetic states. Further investigations into the magnetic thermal evolution under varying probe fields reveal the system's transition into a spin-glass-like state at low temperatures. We attribute the origin of this unconventional exchange bias to the intricate exchange interactions within the spin-glass-like regions that manifest at the interfaces among highly disordered Fe-nuclei. The formation of Fe-nuclei agglomerates at the sub-nanometer scale is attributed to the alloy's limited glass-forming ability and the nature of the thin-film fabrication process. We propose that this distinctive form of exchange bias represents a novel characteristic of amorphous thin films. [ABSTRACT FROM AUTHOR]

The effects of La/Ho co-substitution on multiferroic characteristics were investigated for BiFeO3 ceramics together with structure evolution. The symmetry in Bi1−x(La0.65Ho0.35)xFeO3 ceramics changed from R3c to Pna21 and finally Pbnm with increasing x. Ferroelectricity was significantly improved with La/Ho co-substitution, and Pr reached the maximum of 30.9 μC/cm2 at 160 kV/cm at x = 0.16, where the R3c/Pna21 morphotropic phase boundary was determined. The weak ferromagnetism was released as the symmetry changed from R3c to Pna21, and subsequently the saturated M–H loop could be determined gradually with increasing x, and Mr increased continuously. The electric field-controlled magnetism could be characterized by the significant magnetism variation due to the electric field-induced transition of Pna21/R3c, which occurred during the poling process, and this transition became reversible by the help of annealing after poling. Compared with the situation of Bi1−xNdxFeO3 (the ion radius is the same as the effective one of La0.65Ho0.35), the present co-substituted BiFeO3 ceramics exhibited superior electric field-induced transition of Pna21/R3c with a maximum change rate of 47.03% in remanent magnetization under an electric field, which enhanced the magnetoelectric effect. [ABSTRACT FROM AUTHOR]

Pointed magnetic elements are introduced as an improvement upon rectangular strips currently employed in composite element magnetic barcodes. The coercivity of these elements, as measured using the magneto-optic Kerr effect, is found to strictly adhere to a single power law relationship with the element width, where the power law exponent is dependent on the length of the pointed region and takes values between − 0.98 and − 0.91. The steeper gradients here, along with the absence of the crossover region seen in rectangular devices, present these structures as a strict improvement in terms of potential device applications. These improvements are found to be present for all structures where the pointed region is as long as, or longer than, the magnetic element is wide. The remanent magnetization configuration, imaged using photo-emission microscopy with contrast from x-ray magnetic circular dichroism (XMCD-PEEM), is compared to the results of micromagnetic simulations. It is found to cant inward in the pointed section of the strip, aligning with the edges of the point, pinning the magnetization and giving a consistent magnetization reversal behavior for all element widths investigated. [ABSTRACT FROM AUTHOR]

The movement history of boulders is crucial for the reconstruction of paleo‐tsunamis. We report findings from viscous remanent magnetization studies of the boulders on Tongatapu Island, aiming to reconstruct their reworkings. Two boulders exhibited viscous remanence, whereas two larger boulders lacked viscous components but exhibited stable remanence. Both the viscous and stable components deviated from the geomagnetic field direction. These observations indicate that: (a) the boulders with a viscous component were reworked before the latest event, which could have reworked all boulders, and (b) the magnitude of the latest event was larger than that of an earlier event. The reworked timing indicated that the event occurred between 3,000 years ago and the fifteenth century. The difference in the wave height required to move boulders on the eastern and western coasts suggests that the source of the earlier tsunami was likely an eruption due to volcanoes along the Tonga Ridge. Plain Language Summary: This study explores prehistoric tsunamis on Tongatapu Island by examining large rocks transported during the past tsunamis. Upon analyzing the magnetic records of the rocks, we discovered evidence of multiple rock movements, shedding light on the recurrence and magnitude of past events. Magnetic measurements and previously dated latest movement ages revealed that a tsunami occurred between 3,000 years ago and the fifteenth century. Considering the mobility and immobility of the large rocks and their sizes, the data suggest a smaller paleo‐tsunami magnitude than that of the fifteenth‐century event that transported all the rocks; this expands our understanding of natural hazard history and has implications for assessing tsunami risks in the region. The approach adopted here provides a valuable model for investigating historical natural disasters and their impact on coastal areas, offering insights to enhance global tsunami hazard assessment strategies. Key Points: Viscous remanent magnetization of large boulders indicates multiple reworkings, enhancing our understanding of past tsunamis in TongatapuCombined magnetic records and published radiocarbon ages suggest tsunamis occurred between 3,000 years ago and the fifteenth centuryRemanence and wave height estimates show that the older tsunami was smaller than the fifteenth‐century event, with a possible volcanic source [ABSTRACT FROM AUTHOR]

Bi 1-y Sm y Fe 1-x Ti x O 3 ceramics with compositions at the rhombohedral- orthorhombic morphotropic phase boundary (y = 0.1, 0.12, 0 ≤ x ≤ 0.1) were prepared by solid state reaction method. Analysis of the crystal structure of the compounds based on the results of laboratory and synchrotron X-ray diffraction measurements as well as Raman spectroscopy experiments revealed a coexistence of the rhombohedral phase (SG R 3 c) and the anti-polar orthorhombic phase (SG Pbam) in the compounds Bi 0.88 Sm 0.12 Fe 1-x Ti x O 3 with 0 ≤ x ≤ 0.1; the compounds Bi 0.9 Sm 0.10 Fe 1-x Ti x O 3 are characterized by the mixed structural state for the concentration range 0 ≤ x ≤ 0.06 and by the single phase rhombohedral state within 0.06 < x ≤ 0.1. Room temperature magnetization measurements demonstrate a gradual increase of remanent magnetization with Ti content in the compounds of both systems up to the maximal value of M R ∼0.28 emu/g for compounds with x = 0.06 which is followed by a decrease in magnetization with further titanium doping. Temperature decrease leads to a reduction of remanent magnetization which is mainly caused by a partial recovery of spatially modulated spin structure occurred in the compounds of both systems. Time aging of the compounds for about ∼1 year leads to a drastic increase of M R , which is caused by a change in the structural phase ratio, homogeneity of the structural state and a contribution of unbounded spins demonstrated by low field measurements. Subjecting of the annealed compounds to external electric field of E ∼40 kV/cm leads to a decrease of magnetization associated with backward structural transformations and redistribution of the local structural defects in the compounds. [ABSTRACT FROM AUTHOR]

The occurrences of various illegal activities on beaches require effective geological and environmental investigation methods. Among these methods, the room‐temperature magnetic analysis of soils and sediments represents a nondestructive investigation method for various amounts, types, and grain sizes of magnetic minerals. Here, to verify the usefulness of magnetic analysis in forensic geology research, beach sediment samples from nine sites in the Shimokita Peninsula, Japan, were measured using magnetic analysis to determine the correlations between their concentration‐dependent magnetic parameters and actual regional characteristics. The results revealed that the values of various parameters, namely the low‐field magnetic susceptibility, anhysteretic remanent magnetization, and isothermal remanent magnetization (IRM), were relatively higher at sites near Ti and Fe sedimentary ore deposits. Further, thermomagnetometry results revealed that magnetite was the main magnetic carrier of the sediments. Moreover, pyrrhotite was detected around Ti–Fe mine sites. Furthermore, the results of the investigated parameters reflected the regional characteristics of the amount of magnetic minerals in the beach sediments. Low‐temperature IRM curves and the magnetic grain size parameter also displayed sample‐site‐reflective characteristics. Thus, we believe that magnetic analysis represents an effective method for estimating the provenance of beach sediments in forensic geology research. [ABSTRACT FROM AUTHOR]

In this study, we synthesize pristine and (Mg, Fe) co-doped SnO 2 nanoparticles using the chemical co-precipitation method, where the Mg doping amount is fixed (2 mol%) and the amount of Fe is varied between 2 and 6 mol%. The narrow and sharp natures of intense XRD peaks notify that the crystallinity is pretty well. The formation of the single-phase tetragonal rutile type structure of all prepared compounds has been identified by Rietveld refinement, Fourier-transform infrared spectroscopy (FTIR), and Raman spectroscopy. Moreover, the well incorporation of Fe and Mg in SnO 2 and absence of any other unexpected elements are confirmed by the energy dispersive X-ray spectroscopy. How the co-doping of Mg and Fe alter the crystallite size, microstrain, and dislocation density of the prepared samples have been investigated by Scherrer method with various modified version of it, Williamson-Hall method (W–H) in three factions (UDM, USDM, and UDEDM), Size strain plot (SSP) method, Halder-Wagner (H–W) method, Wagner-Aqua (W-A) method, and Warren-Averbach (WA) method. The obtained crystallite size using the WA method is smaller than the other methods and Scherrer-based methods show much comparable (except SLMSE) sizes. Additionally, the W–H, H–W, SSP, and W-A plots show almost similar tendency of decreasing crystal size, increasing dislocation density and lattice strain with increasing doping. The scanning electron microscopy (SEM) profiles revealed that the synthesized nanoparticles are agglomerated in nature, where the agglomeration increases with decreasing crystal size. The magnetic response of the prepared samples revealed a weak ferromagnetic (or soft magnetic) nature, where saturation magnetization increased due to doping, and a reducing trend of remanent magnetization and coercivity was explored which indicates the phase transition from ferromagnetic to paramagnetic. However, this soft magnetic nature was modified with the influence of defects like changes in lattice parameters, strain, and oxygen vacancy. This phase transition at higher doping concentration makes our nanomaterial as a suitable contender for memory devices, hyperthermia treatment, and photothermal effect. [ABSTRACT FROM AUTHOR]

The utilization of magnetoelectric composites, particularly core-shell configurations, enhances their versatile applications in various sectors such as medicine and data storage. Among these composites, the perovskite-spinel combination is distinguished by its significant potential. A series of (1-x) BiFeO 3 -(x) CoFe 2 O 4 (where x = 0.0, 0.2, 0.5, and 1.0) nano core-shell structures were synthesized using a sol-gel auto-combustion method to explore their multifunctional capabilities. Structural analyses identified peaks corresponding to both perovskite and spinel phases. Field Emission Scanning Electron Microscopy revealed a reduction in average particle size with an increase in CoFe 2 O 4 content.The particle size in the BFO80-CFO20 sample has been reduced from 243 nm to 34 nm. Additionally, Transmission Electron Microscopy images of the BFO80-CFO20 sample highlighted the evolution of core-shell structures. Our findings indicate that higher CFO concentrations significantly affect the dielectric, ferroelectric, and optical properties. The bandgaps of the nanocomposites BFO80-CFO20 and BFO50-CFO50 were estimated to be 1.43 eV and 1.39 eV, respectively. Magnetic analysis showed increases in both saturation magnetization and remanent magnetization with increased CFO content, while the coercive field followed a different trend. The saturation magnetization values for the samples BFO, BFO80-CFO20, BFO50-CFO50, and CFO were calculated as 0.205, 14.612, 28.374, and 74.105 (e m u g r) , respectively. The measured values for the same samples were 0.08, 5.07, 11.34, and 34.01 (e m u g r) , respectively. Further, the electrochemical properties were thoroughly investigated using cyclic voltammetry, linear sweep voltammetry, and electrochemical impedance spectroscopy. [ABSTRACT FROM AUTHOR]

Ce substitution of Nd in FeNdB sintered magnets is very interesting for reasons of resource efficiency, sustainability and costs. However, the magnetic properties of high Ce‐content magnets are poor. This is mainly due to the lower values of intrinsic magnetic properties of Fe14Ce2B compared to Fe14Nd2B as well as the Laves phase Fe2Ce, which is formed in the grain boundaries and forms flat aggregates for higher Ce‐content. In this article, sintered magnets with 75 at% degree of substitution of the composition Fe70.9–[(Ce1−xLax)0.75Nd0.25]18.8–B5.8–M4.5 (M = Co, Ti, Al, Ga, Cu, 0 ≤ x ≤ 0.3) are produced and analyzed. It is shown that a new rare earth rich grain boundary phase is formed adding La and that the Laves phase fraction can be reduced by up to 85%. With increasing La content, the remanence and Curie temperature increase and the temperature coefficient of Hc improves. A coercivity, remanence, and maximum energy density of up to μ0Hc = 0.74 T, Jr = 0.98 T, and (BH)max = 139.9 kJ m−3 have been achieved. [ABSTRACT FROM AUTHOR]

In this study, the effects of the length-to-width ratio on the magnetic and microstructural properties of die-upset Nd–Fe–B magnets were examined. A die-upset magnet with a uniform shape and no significant cracking was successfully developed. During the die-upset process, the applied pressure was not uniform across the magnet and varied depending on its shape and position. In the case of the magnet with a 4:1 ratio, which had the largest length-to-width ratio, there was a higher concentration of stress at the edges compared to the center, resulting in easier grain deformation and growth at the edges, which led to the lowest remanence and (BH)max. As the length-to-width ratio approached 1:1, the grain size increased slightly, reducing the coercivity; however, the magnets maintained a uniform grain-size distribution. The change from a rectangular to a square pressing surface resulted in a more uniform stress distribution, particularly at the center and corners, which improved the consistency of the magnetic properties across different regions of the magnet. Consequently, an 11.9% enhancement in (BH)max, reaching 285.6 kJ/m3, was achieved in the 1:1 ratio die-upset magnet, which is attributed to the uniform grain size and improved grain alignment. [ABSTRACT FROM AUTHOR]

This study investigates the impact of zirconium substitution on the structural, elastic and magnetic properties of CoCr2O4 nanoparticles. A series of CoCr2−xZrxO4 nanoparticles, x = 0.00, 0.05, 0.10, 0.15 and 0.20, are synthesized via the co-precipitation method. X-ray diffraction (XRD) patterns affirm the formation of single-phase cubic structure with the space group Fd3m. Special attention is given to accurately calculating the average crystallite size (D) and lattice parameter (a) using Williamson–Hall (W–H) analysis and the Nelson–Riley (N–R) extrapolation function, respectively. The increase in Zr4+ content leads to a reduction in crystallite size and an increase in the lattice parameter. Elastic properties are estimated from force constants and the lattice constant, determined from FTIR and XRD, respectively. The observed changes in the elastic constants are attributed to the strength of interatomic bonding. The stiffness constants decrease, while Poisson's ratio increases with increasing Zr4+ content, reflecting the increase in the ductility of the prepared samples. As the Zr4+ content increases, the stiffness constants decrease, and Poisson's ratio increases, reflecting enhanced ductility of the samples. Furthermore, as Zr4+ content rises, Young's modulus, the rigidity modulus and Debye temperature decrease. The magnetic hysteresis loop measurements are carried out at room temperature using a vibrating sample magnetometer (VSM) over a field range of 25 kg. Unsubstituted CoCr2O4 exhibits ferrimagnetic behavior. As Zr4+ content increases, saturation magnetization (Ms) and magnetic moment decrease, while remanent magnetization (Mr) and coercivity (Hc) initially decrease up to x = 0.10, then increase with further increases in x. The novel key of this study is how Zr4+ substitution in CoCr2O4 nanoparticles can effectively modify their elastic moduli and magnetic properties, making them suitable for various applications such as flexible electronics, protective coatings, energy storage components and biomedical implants. [ABSTRACT FROM AUTHOR]

A basaltic lava flow erupted from the Tajogaite volcano on 4 December 2021, in La Palma (Canary Islands, Spain) was sampled to find out to what extent reliable and correct information on both intensity and direction of the Earth's magnetic field can be obtained from the palaeomagnetic signal recorded in a lava flow which erupted under known conditions. Samples were taken every few centimetres across a flow up to a total of 27 oriented cores. Palaeomagnetic experiments showed a strong viscous overprint in many samples. Nevertheless, the mean palaeomagnetic direction obtained agrees well with the actual value from IGRF-13. Rock magnetic experiments were performed to obtain additional information about the quality and reliability of the results and the reasons for unsuccessful determinations. Analysis of mostly irreversible thermomagnetic curves showed that the carriers of remanence were magnetite and titanomagnetite of low and/or intermediate Curie-temperature. Hysteresis parameter ratios showed a pronounced variability across the flow. Analyses of frequency dependent susceptibility, IRM acquisition coercivity spectra and FORCs showed a noticeably presence of very low coercivity grains (multidomain and superparamagnetic-single domain boundary). Multimethod palaeointensity experiments were performed with the Thellier-Coe, multispecimen and Tsunakawa-Shaw methods. Only three of 25 cores from the flow yielded successful Thellier-Coe determinations, in agreement with the expected field value of 38.7 μT (IGRF-13). However, palaeointensities of 60 per cent of the specimens agree with the expected value performing an informal analysis without considering criteria thresholds. Four of six Tsunakawa-Shaw determinations performed on samples from the flow yielded correct results, but three multispecimen determinations providing apparently successful determinations largely underestimate the expected field intensity. Combination of three Thellier-Coe and four Tsunakawa-Shaw successful determinations yields a multimethod palaeointensity result B = (36.9 ± 2.0) μT in good agreement with the expected field intensity. [ABSTRACT FROM AUTHOR]

We adapted a recently developed technique of oriented drill coring (100 m in depth) for paleomagnetic measurements, including additional techniques such as half-cutting of the drill cores and accurate cube sampling using an apparatus that precisely guides the cube into the half-cut drill core surface. Our techniques were successfully applied to sequential tephra layers (including loess) at Akan Quaternary caldera volcano in eastern Hokkaido, Japan. Directions of remanent magnetization for a total of 129 specimens were measured by Spinner magnetometer with thermal and alternating field demagnetizations. We detected clear Matuyama–Brunhes geomagnetic reversal between the depths of 20.59 m and 21.30 m, where inclinations change from 65.1 to –44.3°. With these techniques, we can in future obtain useful geologic information (e.g., radiometric ages and absolute paleo-intensities) from volcanic rocks around the Matuyama–Brunhes boundary in Akan volcano. This will clarify more detailed processes of the geomagnetic polarity transition. Our study demonstrates the utility of oriented drill cores from successive tephra and loess layers for high resolution investigate of continuous paleo-geomagnetic records. The new techniques can be adopted to other geological fields on Earth, like in studies of marine sediments, providing continuous paleomagnetic direction data from drill core. [ABSTRACT FROM AUTHOR]

This work focuses on the study of the microstructure and magnetic properties of nanocrystalline powders of Sm4ZrFe33, prepared by high‐energy ball milling. The Sm4ZrFe33 compound adopts a monoclinic structure (space group Cm). Upon annealing, these Sm4ZrFe33 samples exhibit notable variations in their extrinsic magnetic properties, closely linked to temperature fluctuations. The investigation delves into the correlation between morphology, grain size and magnetic characteristics. A significant enhancement in coercivity (Hc), remanent magnetization (Mr), and maximum energy product ((BH)max) is observed, primarily attributed to the finer grain structure present in the samples. Particularly noteworthy, among all annealed specimens, the nanocrystalline Sm4ZrFe33 compound annealed at a temperature of Ta = 973 K demonstrates the most promising magnetic properties. This specimen exhibits a coercivity Hc of 18 500 Oe, remanent magnetization (Mr) of 58 emu g−1, maximum energy product ((BH)max) of 5.18 MGOe, Curie temperature (TC) of ≈804 K, and magnetic anisotropy field (Ha) of 115 980 Oe. These research findings pave the way for future investigations and applications in the realm of permanent magnets, spintronic devices, and magnetic recording, utilizing nanocrystalline alloys based on the Sm4ZrFe33 compound. [ABSTRACT FROM AUTHOR]

Y1-xNdxFe1-yNiyO3 (x = 0, y = 0; x = 0.05, y = 0.05; x = 0.05, y = 0.10; x = 0.05, y = 0.15) powders with different concentrations of Nd3+ and Ni2+ doped ions were synthesized by sol-gel method. The structure, morphology, and magnetic properties of the materials were characterized by powder X-ray diffraction (XRD), scanning electron microscope (SEM), and physical property measurement system (PPMS). X-Ray diffraction results show that all the prepared samples are in the single perovskite phase without any secondary phases. The measured doping content was basically consistent with the initial designed content. The remanent magnetization (Mr) and saturation magnetization (Ms) of the synthesized YFeO3 were 0.701 emu/g and 1.481 emu/g, respectively, and the coercivity (Hc) reached 19,000 Oe. The results also showed that the Mr and Ms values of YFeO3 increase, while the Hc values decrease with increasing Ni2+ ion content. When the doping concentrations are x = 0.05 and y = 0.15, the values of Mr and Ms are 0.787 emu/g and 1.782 emu/g, respectively, with Hc at 2100 Oe. From the research results, it can be observed that the introduction of doped ions enhances the super-exchange interactions. [ABSTRACT FROM AUTHOR]

Mineral fabrics within igneous intrusions can archive both tectonic and magmatic processes. However, whether magmatic state fabrics reflect primary magmatic processes or regional tectonic strain is often ambiguous. To investigate when fabrics are formed, one can compare the mineral fabrics to primary magmatic features, such as the interface between solidified magmas in mingling zones. The monzodioritic Fanad pluton shows a NNE-SSW–aligned petrofabric parallel to the strike of a nearby shear zone, with dioritic enclaves aligned parallel and oblique to this petrofabric. We therefore aimed to test if the enclaves’ internal fabrics are passive and align with enclave morphology or result from progressive overprint by regional tectonic strain. Crystallographic preferred orientation and anisotropy of magnetic susceptibility data from all enclaves and the host monzodiorite revealed a NNE-SSW petrofabric parallel to the regional tectonomagmatic fabric. However, anisotropy of anhysteretic remanent magnetization data within petrofabric-oblique enclaves revealed a primary fabric parallel to the enclave long axis. Therefore, we interpret enclave morphologies to reflect earlier magmatic state deformation, with fabrics being realigned to regional tectonic deformation. These two distinct petrofabrics were interpreted in the context of the magmatic processes and the evolving late Caledonian paleostress field, with earlier magma processes distinguished from subsequent tectonic overprinting occurring in the magmatic state. Our new data show that multiple fabrics are preserved within enclaves even though all fabric development occurred within a magmatic state. Our results also show that enclaves can effectively record successive strain events, providing new insight with which to decipher tectonomagmatic processes. [ABSTRACT FROM AUTHOR]

Speleothems are mineral deposits capable of recording detrital and/or chemical remanent magnetization at annual timescales. They can offer high‐resolution paleomagnetic records of short‐term variations in Earth's magnetic field, crucial for understanding the evolution of the dynamo. Owing to limitations on the magnetic moment sensitivity of commercial cryogenic rock magnetometers (∼10−11 Am2), paleomagnetic studies of speleothems have been limited to samples with volumes of several hundreds of mm3, averaging tens to hundreds of years of magnetic variation. Nonetheless, smaller samples (∼1–10 mm3) can be measured using superconducting quantum interference device (SQUID) microscopy, with a sensitivity better than ∼10−15 Am2. To determine the application of SQUID microscopy for obtaining robust high‐resolution records from small‐volume speleothem samples, we analyzed three different stalagmites collected from Lapa dos Morcegos Cave (Portugal), Pau d'Alho Cave (Brazil), and Crevice Cave (United States). These stalagmites are representative of a range of magnetic properties and have been previously studied with conventional rock magnetometers. We show that by using SQUID microscopy we can achieve a five‐fold improvement in temporal resolution for samples with higher abundances of magnetic carriers (e.g., Pau d'Alho Cave and Lapa dos Morcegos Cave). In contrast, speleothems with low abundances of magnetic carriers (e.g., Crevice Cave) do not benefit from higher resolution analysis and are best analyzed using conventional rock magnetometers. Overall, by targeting speleothem samples with high concentrations of magnetic carriers we can increase the temporal resolution of magnetic records, setting the stage for resolving geomagnetic variations at short time scales. Plain Language Summary: Earth has a magnetic field that is generated in the outer core, and through paleomagnetism we can retrieve information about the evolution of the field from rocks. Different types of rocks have been used to determine how Earth's magnetic field has changed over time. In this study, we use magnetic microscopy to analyze the magnetic record of speleothems, which are rocks that form inside caves and that can record magnetic fields in annual scales. This allows us to obtain magnetic records with higher resolution than previous studies. This is important because Earth's magnetic field changes in timescales ranging from thousands of years to a few years, and obtaining records from speleothems using magnetic microscopy can help us track these variations. We provide data demonstrating how the technique can be used and showing its limitations, and we discuss how the geologic context of the cave influences the robustness of the magnetic record. We also provide protocols for future studies using magnetic microscopy in speleothems. Key Points: Magnetic microscopy can be used to produce a 5× improvement in temporal resolution of magnetic records from speleothemsVariations in magnetic properties across speleothems can affect the temporal resolution of the magnetic recordProtocols for conducting high‐resolution magnetic measurements of speleothems with magnetic microscopy are presented [ABSTRACT FROM AUTHOR]

The effect of substituting Sn with a fourth element on the functional properties of Heusler NiMnSn alloys has been reported in the literature. In the present work, the influence of the addition of Si to the Heusler NiMnSn system was evaluated, where Ni44Mn44Sn12 (at.%), Ni44Mn44Sn10.5Si1.5 (at.%) and Ni44Mn44Sn9Si3 (at.%) alloys were prepared in an induction furnace without a controlled atmosphere, and were later characterized by optical microscopy, Vickers microhardness, electrical resistivity, and vibrating sample magnetometry. The results revealed that the partial replacement of Sn by 3 at.% Si did not modify the dendritic microstructure and the phases present at room temperature; however, it increased the percentage of the martensite phase from 51% to 76%. This modification in the percentage of this phase is responsible for reducing the average Vickers microhardness values (from 469 HV to 459 HV), increasing the electrical resistivity (from 1.3 mΩ mm to 2.21 mΩ mm), and decreasing the saturation magnetization (from 23.67 emu/g to 19.34 emu/g), coercivity (from 5.56 Oe to 5.14 Oe), and remanent magnetization (from 0.21 emu/g to 0.18 emu/g). With this, our results bring to light a new alternative for doping the NiMnSn alloy as a way of modifying the structural and electrical properties, constituting interesting parameters for technological applications. [ABSTRACT FROM AUTHOR]

Nanostructured Fe90Si10 powders were synthesized through a mechanical alloying process to explore the impact of milling duration on both their magnetic behavior and structural properties. Our investigation involved a comprehensive analysis encompassing morphological, magnetic, and structural characterizations, employing scanning electron microscopy (SEM) coupled with energy-dispersive x-ray spectroscopy (EDS), a vibrating sample magnetometer, and x-ray diffraction (XRD). XRD analysis unveiled the formation of a disordered Fe90Si10 solid solution exhibiting a body-centered cubic crystal structure after 15 h of milling. With increasing milling time, the lattice parameter gradually increased from 0.2861 nm for the unmilled Fe90Si10 powder to 0.4528 nm after 30 h of milling. The sample subjected to 30 h of milling revealed an average crystallite size of 19.51 ± 0.03 nm, accompanied by noteworthy lattice deformation (0.236 ± 0.006%). To assess morphological evolution and elemental composition homogeneity during milling, SEM and EDS analyses were employed, respectively. For nanostructured Fe90Si10, we examined coercivity (Hc), magnetization saturation (Ms), remanent magnetization (Mr), and squareness (Mr/Ms) as functions of milling time through hysteresis loop measurements. The highest values for Hc, Ms, Mr, and Mr/Ms were achieved after 30 h. This study elucidates the intricate relationship between mechanical milling duration and the magnetic and structural properties of nanostructured Fe90Si10, providing valuable insights into their potential applications across various fields. [ABSTRACT FROM AUTHOR]

In the present work, we have investigated the crystal structure and magnetic properties of the Y2.97Gd0.03Fe5−xLaxO12 (Gd-La co-doped YIG) compound (0.00 ≤ x ≤ 0.05) obtained by the citrate sol–gel method. Rietveld refinement of the X-ray diffraction patterns provided the lattice parameter (a) values, which increased from 12.387(2) to 12.468(2) Å as the La3+ content increased. Raman measurements confirmed the single-phase formation, whereas transmission electron microscopy (TEM) revealed elongated and irregular particles. The Mössbauer spectroscopy confirmed the presence of Fe3+ and Fe2+ cations and the coexistence of Fe2+ and La3+ cations in the octahedral and tetrahedral sites. Nonetheless, using a phenomenological model, it was suggested that the Fe2+ and La3+ ions tend to occupy preferentially the octahedral sites in the YIG structure. Further, the correspondence between the experimental and theoretically predicted saturation magnetization values indicated that the compound stoichiometry can be described by the chemical formula Y3+2.97Gd3+0.03Fe3+5−x−yLa3+xFe2+yO2−12−y/2. Magnetic parameters such as saturation magnetization, anisotropy constant, remanent magnetization, and coercive field values were computed and discussed as a function of cations distribution in the YIG crystal structure. [ABSTRACT FROM AUTHOR]

Metal-bonded magnetic composites (MBMCs) present a promising alternative to dense sintered magnets, particularly for intricate components. Compared to polymer-based bonded magnets, MBMCs have wider applicability in harsh environments. In this paper, we demonstrate a solid-state shear-based manufacturing technique to introduce localized magnetization into a paramagnetic aluminum matrix by embedding SmCo5 permanent magnet particles. Our magnetic composites display hard magnetic behavior with a coercivity of 13 kOe and a remanent magnetization of 4.32 emu/g. In addition to magnetization, we also report a 9% improvement in Young's modulus. Despite the local temperature rise during processing, the magnetic phases didn't decompose into unwanted phases, preserving the composite's hard magnetic properties. Creation of an interfacial metallurgical bond with the matrix ensured the suitability of the composites for structural applications. Our study investigates the mechanical, and functional properties of composites, paving the way for lightweight structural magnetic composites with a transformative potential in the aerospace, nuclear, and automotive applications. This work underscores the potential for further optimization and development to drive innovations in magnet and equipment design. [ABSTRACT FROM AUTHOR]

Viscous remanent magnetization (VRM) in multidomain (MD) particles has many puzzling properties that deviate from the current VRM theory, based on Néel's single‐domain model of magnetic particles with an almost symmetric double‐well potential. In larger magnetic particles experimental evidence indicates that more complex magnetization structures preferentially change from high‐energy states to low‐energy states with large energy differences, such that VRM is preferentially acquired by directed magnetization changes in strongly asymmetric double‐well potentials. Here, a statistical model based on this 'trapdoor' VRM (tdVRM) naturally explains the experimental observations of initial‐state dependence, time‐lag variation, non‐linear logt $\log \,t$ dependence, and acquisition‐decay asymmetry for MD VRM. It is discussed how tdVRM can be experimentally distinguished from single‐domain VRM and how the new theory can help to improve age determination by VRM analysis. Plain Language Summary: The magnetization of rocks is an important property used to determine the history of the Earth surface and variations of Earth's magnetic field. Magnetite particles in rocks are abundant recorders of this field, and particles larger than about 500 nm in diameter are called multidomain (MD) magnetites. If a rock, after its formation, lies at Earth's surface for a long time, its magnetization slowly changes—the newly acquired remanent magnetization is called a viscous remanent magnetization (VRM). This VRM is well understood for magnetite particles below about 150 nm in diameter, but no comprehensive theory so far explains all its experimentally observed properties. Here a statistical model is developed that can explain the experimental facts and helps to understand their physical origin. The new theory allows theoretical investigation of different methods to determine the amount of time a rock was exposed to Earth's present‐day magnetic field. This leads to a better understanding of time‐temperature relations for VRM, and improves the determination of relocation ages based on VRM. Key Points: Multidomain viscous remanent magnetization (MD VRM) is dominated by decay into trapdoor potential minimaPreviously inexplicable properties of MD VRM are explained by a quantitative trapdoor VRM theoryTrapdoor VRM suggests an improved method for VRM age determination [ABSTRACT FROM AUTHOR]

Metropolitan Mexico City (MMC) children and young adults exhibit overlapping Alzheimer and Parkinsons' diseases (AD, PD) and TAR DNA-binding protein 43 pathology with magnetic ultrafine particulate matter (UFPM) and industrial nanoparticles (NPs). We studied magnetophoresis, electron microscopy and energy-dispersive X-ray spectrometry in 203 brain samples from 14 children, 27 adults, and 27 ALS cases/controls. Saturation isothermal remanent magnetization (SIRM), capturing magnetically unstable FeNPs ~ 20nm, was higher in caudate, thalamus, hippocampus, putamen, and motor regions with subcortical vs. cortical higher SIRM in MMC = 40y. Motion behavior was associated with magnetic exposures 25-100 mT and children exhibited IRM saturated curves at 50-300 mT associated to change in NPs position and/or orientation in situ. Targeted magnetic profiles moving under AC/AD magnetic fields could distinguish ALS vs. controls. Motor neuron magnetic NPs accumulation potentially interferes with action potentials, ion channels, nuclear pores and enhances the membrane insertion process when coated with lipopolysaccharides. TEM and EDX showed 7-20 nm NP Fe, Ti, Co, Ni, V, Hg, W, Al, Zn, Ag, Si, S, Br, Ce, La, and Pr in abnormal neural and vascular organelles. Brain accumulation of magnetic unstable particles start in childhood and cytotoxic, hyperthermia, free radical formation, and NPs motion associated to 30-50 μT (DC magnetic fields) are critical given ubiquitous electric and magnetic fields exposures could induce motion behavior and neural damage. Magnetic UFPM/NPs are a fatal brain cargo in children's brains, and a preventable AD, PD, FTLD, ALS environmental threat. Billions of people are at risk. We are clearly poisoning ourselves. [ABSTRACT FROM AUTHOR]

The influence of size on the dynamic magnetic hysteresis properties and dynamic phase transitions of Fe and F e 3 O 4 2D-circular nanodisks with varying diameters has been explored in the micromagnetic framework. This investigation is conducted under a sinusoidal dynamic magnetic field along the x-direction by solving the Landau-Lifshitz-Gilbert (LLG) equation with the OOMMF software at zero temperature. The dynamic hysteresis of nanodisks is profoundly impacted by both the frequency and amplitude of the applied external field, along with the particle size. As particle size decreases, there is an observed increase in the frequency values at which the transition to dynamic ordered frequency occurs in Fe nanodisks, whereas a decrease is noted in the transition frequency values of F e 3 O 4 nanodisks. [ABSTRACT FROM AUTHOR]

We designed an electromagnetic microactuator with tunable dynamic characteristics using a thick-film FePt permanent magnet. FePt is a promising microactuator material because of its low Young's modulus, high tensile strength, high ultimate strain as a structural material, and high remanence as a permanent magnet. By employing the laser-assisted heating magnetization method, we successfully reprogrammed the magnetization pattern of the FePt thick film, which led to the tuning of the dynamic characteristics of the 3.85 mm (l) × 0.82 mm (w) × 0.023 mm (t) FePt-based cantilever under the same alternating external magnetic field. When only the tip of the cantilever beam is magnetized, or when the tip and center of the same beam are magnetized in opposite phases, the peak gain of the frequency response characteristics of the former can be tuned to be 19 dB higher than that of the latter in the first-order mode and 19 dB lower than that of the latter in the second-order mode. [ABSTRACT FROM AUTHOR]

The Cuo E (CE) core contains the entire Quaternary stratigraphy of the CE Lake (31°24′–31°.32′ N, 91°28′–91°33′E, Tibetan Plateau, China). Here, we study the magnetic properties of 1,748 samples from the CE core, combined with scanning electron microscopy and X‐ray energy dispersive spectrometer analysis on selected samples. The main magnetic minerals appear to be magnetite and greigite. To further quantify the presence of greigite in CE core, 84 samples were analyzed using rock magnetism in more detail including: susceptibility (χ) versus temperature, coercivity component analysis of acquisition curves of the isothermal remanent magnetization (IRM), and principal component analysis of the first‐order reversal curve (FORC) diagrams. The greigite content and saturation IRM over susceptibility (SIRM/χ) appear to be exponentially related. SIRM/χ can be used as greigite concentration indicator. We also propose a rapid way to identify greigite in the CE core: When SIRM/χ increases and anhysteretic remanent susceptibility (χARM) increases only slowly, the sample contains greigite. Samples with SIRM/χ < 15 kA/m also follow this relation. This greigite detection method has a lower limit of detection than the traditionally used SIRM/χ parameter. It is also faster than FORC analysis and thus particularly suitable for analysis of large sample collections. Twenty greigite‐bearing layers were identified in the CE core using this method. The location of the Jaramillo subchron in the CE core is controversial in the currently available magnetostratigraphy, possibly related to the presence of greigite in this core interval. Plain Language Summary: Paleomagnetic chronology is an important geological dating tool for sediment cores or sections that span sufficient duration, and one of its prerequisites is the identification of magnetic minerals. Greigite (Fe3S4) is a magnetic mineral that acquires its natural remanent magnetization at any time during diagenesis, so its presence has bearing on the accuracy of magnetic stratigraphy. In this work, we used rock magnetic methods to identify magnetite (Fe3O4) and greigite as the main magnetic minerals in the CE core on the Qinghai Tibet Plateau (China). We also semi‐quantitatively express the greigite amount and propose a rapid greigite identification method. This method is faster and simpler than other rock magnetic methods and thus particularly suitable for analysis of large sample collections. The approach also provides a framework for research into greigite and magnetic stratigraphy. Key Points: A rapid method to identify greigite is proposed, which is also applicable to samples with low SIRM/χSIRM/χ can be used as greigite concentration indicator and not only to indicate greigite above a certain thresholdTwenty layers of greigite were identified in the Cuo E core, which may be the cause of its inaccurate magnetic stratigraphy [ABSTRACT FROM AUTHOR]

We perform a joint analysis of gravity and magnetic data sets in the Tyrrhenian Sea region to infer the rock physical properties of several volcanic seamounts. We propose a moving‐window application using Poisson's theorem, which relates the total gradient of the magnetic field to the total gradient of the first‐order vertical derivative of the gravity field data. In volcanic environments, where strong intensity of remanent magnetization is expected, the total gradient of the magnetic field is particularly useful since it is almost independent on the direction of the total‐magnetization. The moving‐window approach resulted necessary due to the heterogeneous magnetization distribution of the volcanoes. First, we perform synthetic tests based on realistic seamount models which exhibit inhomogeneous magnetization intensity and orientation. Using the total gradients, we demonstrate that our approach can provide an appropriate magnetization‐to‐density ratio in different subareas of seamounts. The results of the correlation analysis for the Palinuro, Marsili, Vavilov, and Magnaghi seamounts provide interesting information on the variability of magnetization associated with different epochs of formation and demagnetization effects due to hydrothermal alteration processes. Plain Language Summary: We analyzed gravity and magnetic data sets to determine the rock properties of the main seamounts in Southern Tyrrhenian Sea. This study shows that the correlation analysis based on a window‐by‐window approach is an efficient tool for studying potential field anomalies in areas where inhomogeneous distribution of magnetization is expected. We also show that, by studying the total gradients of the magnetic field and the first order vertical derivative of the gravity field, the correlation analysis is almost insensitive to the direction of the remanent magnetization. We obtain interesting information on the variability in magnetization for each seamount and identify possible areas of demagnetization due to hydrothermal alteration processes. Key Points: We may infer the rock magnetization of seamounts by the correlation analysis of gravity and magnetic anomaliesThe study of the potential field total gradients is particularly useful when the source has strong remanent magnetizationWe found inhomogeneous magnetization in the Palinuro, Marsili, Magnaghi and Vavilov seamounts, likely due to hydrothermal activity [ABSTRACT FROM AUTHOR]

In this study, Zn-Al ferrite/polypyrrole (PPy) nanocomposites were synthesized and thoroughly characterized to explore their potential for microwave applications. X-ray diffraction analysis confirmed the presence of ZnO, AlFeO3, and Fe2O3 phases, with the crystal size decreasing from 31 nm to 19.6 nm as aluminum content increased. High-resolution transmission electron microscopy (HR-TEM) revealed a distinctive core–shell morphology, where the polypyrrole encapsulates the ZnAlxFe2−xO4 particles. Magnetic measurements showed that decreasing aluminum concentration led to a reduction in both saturation magnetization (Ms) from 75 emu/g to 36 emu/g and remanent magnetization (Mr) from 2.26 emu/g to 2.00 emu/g. Dielectric analysis indicated that both the real (ε′) and imaginary (ε″) components of dielectric permittivity decreased with increasing frequency, particularly between 10 and 14 GHz. Furthermore, electrical modulus analysis highlighted the significant impact of aluminum doping on relaxation time (τIP), indicating the presence of interface polarization. Impedance spectroscopy results underscored the dominance of interface polarization at lower frequencies and the presence of strong conduction paths at higher frequencies. These combined magnetic and dielectric loss mechanisms suggest that the Zn-Al ferrite/polypyrrole nanocomposite is a promising candidate for advanced microwave absorption applications. [ABSTRACT FROM AUTHOR]

Although Mars today does not have a core dynamo, magnetizations in the Martian crust and in meteorites suggest a magnetic field was present prior to 3.7 billion years (Ga) ago. However, the lack of ancient, oriented Martian bedrock samples available on Earth has prevented accurate estimates of the dynamo's intensity, lifetime, and direction. Constraining the nature and lifetime of the dynamo are vital to understanding the evolution of the Martian interior and the potential habitability of the planet. The Perseverance rover, which is exploring Jezero crater, is providing an unprecedented opportunity to address this gap by acquiring absolutely oriented bedrock samples with estimated ages from ∼2.3 to >4.1 Ga. As a first step in establishing whether these samples could contain records of Martian paleomagnetism, it is important to determine their ferromagnetic mineralogy, the grain sizes of the phases, and the forms of any natural remanent magnetization. Here, we synthesize data from various Perseverance instruments to achieve those goals and discuss the implications for future laboratory paleomagnetic analyses. Using the rover's instrument payload, we find that cored samples likely contain iron oxides enriched in Cr and Ti. The relative proportions of Fe, Ti, and Cr indicate that the phases may be titanomagnetite or Fe‐Ti‐Cr spinels that are ferromagnetic at room temperature, but we cannot rule out the presence of non‐ferromagnetic ulvöspinel, ilmenite, and chromite due to signal mixing. Importantly, the inferred abundance of iron oxides in the samples suggests that even <1 mm‐sized samples will be easily measurable by present‐day magnetometers. Plain Language Summary: Mars today does not have a magnetic field, but laboratory studies of Martian meteorites and spacecraft observations of the Martian crust indicate that Mars's metallic core once generated a magnetic field, known as a core dynamo. Although the dynamo seems to have been active prior to ∼3.7 billion years ago, its strength, direction and lifetime are largely unknown. Determining these characteristics is important for understanding the evolution of the Martian core and to test the theory that the magnetic field played a key role in making ancient Mars habitable. The Perseverance rover is providing a unique opportunity to answer these questions by acquiring bedrock samples that may span the full lifetime of the field. However, to establish whether these samples could tell us about the ancient dynamo, it is important to show they contain minerals with a special property known as ferromagnetism that allows them to record and retain records of the ancient magnetic field. Here, we present evidence the samples contain iron oxide minerals, many of which are known to be ferromagnetic. As such, we expect that future laboratory studies of these samples following their return to Earth will provide powerful constraints on the history of Mars's magnetic field. Key Points: Iron oxides with titanium and chromium components are present in lithologies sampled by the Perseverance rover on MarsThese iron oxides may contain magnetizations from ancient Martian magnetic fieldsReturned samples of these lithologies will constrain the history and characteristics of the Martian dynamo [ABSTRACT FROM AUTHOR]

Hysteresis curves of commercial Alnico 5 and Alnico 2 magnets were evaluated with the anisotropic Stoner-Wohlfarth model. Alnico 2 is an isotropic magnet, whereas Alnico 5 is an anisotropic magnet. These magnets have five main alloying elements: Al, Fe, Ni, Co and Cu. The described method allows a direct estimate of the shape anisotropy in any commercial Alnico magnet, avoiding laborious production of single crystals. Besides, the magnetic anisotropy of any sample with fiber texture can be determined. Parameters related to magnetic shape anisotropy can be directly extracted from the hysteresis of either isotropic or anisotropic Alnico magnets. A shape anisotropy of 1.4 kOe was estimated for the isotropic Alnico 2. The shape anisotropy of the anisotropic Alnico 5 was estimated at 2.2 kOe. The magnetic texture of the Alnico 5 sample can be well described by a Gaussian distribution and remanence to saturation ratio, Mr/Ms, of 0.931. A spring effect is observed in the hysteresis of the Alnico 2 and Alnico 5 magnets, confirming that the ferromagnetic phase is single domain size and that the mechanism of reversal is coherent rotation. [ABSTRACT FROM AUTHOR]

Anisotropic Nd-Fe-B magnets have been fabricated by the hot forward-extrusion method and exhibit the same heterogeneous microstructure characteristics as conventional die-upsetting magnets. It has been found that the magnetic properties on both sides of the magnetic sheet are better than that of the middle zone, and that the magnetic properties of the intermediate zone in the extrusion direction are better than those of the top zone (close to the extrusion die and the latest extruded zone) and the bottom zone (the earliest extruded zone) in the extrusion direction. With the decrease of extrusion speed, the process by which Nd2Fe14B grains become flat platelets with their c-axes parallel to the stress axis by grain rotating and diffusion slip have been more fully completed, while the texture, remanence, and maximum magnetic energy product (BH)max of the forward-extruded magnetic sheet monotonically increased. With the increase of hot-pressing and hot-extrusion temperatures, the texture, remanence, and (BH)max of the hot-extruded magnetic sheet initially increased and then decreased. The magnetic sheet hot-pressed at 550°C and hot-extruded at 850°C with an extrusion speed of 0.05 mm s−1 had the best magnetic properties, its (BH)max being 40.3 MGOe, Br 13.5 kGs, and Hcj 9.8 kOe. [ABSTRACT FROM AUTHOR]

This study on laser powder bed fusion (LPBF) in-situ alloying of Fe-25Cr-15Co (wt.%) permanent magnetic alloy addresses the anisotropy in texture, microstructure, and properties through comprehensive microstructural characterizations. The microstructure, magnetic properties, and mechanical properties of the specimens exhibit anisotropy. The ⟨ 100 ⟩ fiber texture and Goss-type 110 〈001〉 texture are observed in the vertical plane of the as-built sample, which imparts anisotropic magnetic properties to the sample. The longitudinal sample, parallel to the building direction, exhibits superior magnetic properties, with coercivity H c , remanence B r , and energy product (B H) max values of 22.35 kA/m, 0.84 T, and 7.24 kJ/m3, respectively, which are equivalent to those in the isotropic state prepared by traditional methods. Hardness and compression experiments demonstrate that the mechanical properties of the LPBF-built samples are better than those of the as-cast samples. The results of this study validate the feasibility of applying the LPBF in-situ alloying technique to Fe-Cr-Co permanent magnet alloys. This technique makes it possible to further explore the potential of Fe-Cr-Co magnetic materials by freely adjusting the composition and constituents of the materials, and to fabricate components or structures with complex shapes while maintaining excellent magnetic and mechanical properties. [ABSTRACT FROM AUTHOR]

Airborne particulate pollution, which contains heavy metals (HMs) among other contaminants, is associated with many health effects related to respiratory problems, such as cardiopulmonary lesions and systemic diffusion. This study aimed to evaluate the levels of HMs contamination using different plants and monitors, as well as to evaluate the relationship between HMs content and magnetic properties in leaves of different types of biomonitors. For analysis, 180 samples were taken from biomonitors; Cupressus lusitanica (Cupressaceae), Citrus (Rutaceae), and Ficus benjamina (Moraceae), and monitors (road dust, surface and, deep soil). Seven HMs were measured: Cu, Pb, Ni, Cr, Fe, V, and Zn in all samples. Specific susceptibility (χlf), and isothermal remanent magnetization curves (IRM) were assessed in biomonitors samples. The results revealed that the major biomonitor was C. lusitanica, which also showed the highest χlf (20.54 × 10–8 m3/kg) and IRM (2.66 mAm2/kg). Additionally, given the low coercivity of the magnetic material found in the χlf and SIRM values, those magnetic properties can be used interchangeably to determine the magnetic minerals in the biomonitors studied. We conclude that the use of biomonitors and monitors presents a potential to be used as an alternative method for contaminant monitoring and the use of magnetic properties is feasible to measure air pollution. [ABSTRACT FROM AUTHOR]

The nano ferrite compounds Co 1-x Cu x Fe 2-y Ce y O 4 (with x values of 0.0, 0.25, 0.5, and 0.75, and y values of 0.0, 0.03, 0.06, and 0.09) were synthesized through the sol-gel auto-combustion method. The characteristics of spinel ferrites were tailored by creating nano ferrites with desirable properties, which were then sintered at 1150 °C for 2 h in the presence of rare earth (Ce3+) and transition metals (Cu2+). They were investigated using dielectric, FTIR, FESEM, XRD, VSM, and DC electrical resistivity experiments. XRD examination verified the samples' cubic spinel structure by measuring the average crystallite size, x-ray density, and lattice constant. FESEM images revealed grain sizes ranging from 41.07 to 156 nm. FTIR spectra in the range of 415 cm−1 to 430 cm−1 further supported the substitution of Cu2+/Ce3+ ions in the tetrahedral sites, indicated by an increase in the lattice parameter. Measurements of the remanence ratio, saturation magnetization, anisotropy constant, coercivity, and magnetic moment, among other magnetic characteristics, were made. Higher concentrations of Cu2+/Ce3+ ions were found to considerably reduce magnetic saturation (Ms), coercivity (Hc), and remanence (Mr). These materials were semiconducting because their activation energy varied between 0.52 and 0.62 eV, and their DC resistivity increased with increasing Cu2+/Ce3+ concentration. Above 1 MHz, the dielectric properties became frequency-independent and decreased with increasing frequency. These ferrites seem highly potential for devices working at high frequency. [Display omitted] [ABSTRACT FROM AUTHOR]

Magnetic studies of loess–paleosol sequences have shown that the magnetic properties of loess and its parent material are sensitive to weathering degree. However, the relationship between magnetic properties and weathering processes in red soils of southern China remains unclear due to the diversity of parent rocks and the influence of climate. This study focused on red soils developed on weakly magnetic sandstone, in tropical and subtropical regions of Yunnan, China. The principal element content, magnetic susceptibility, temperature-dependent susceptibility curve (χ–T curve, where χ represents the magnetic susceptibility at the corresponding temperature during the heating and cooling process of the sample, and T represents the temperature during the heating and cooling process.), hysteresis loop and Isothermal Remanent Magnetization (IRM) of the samples were determined, the weathering characteristics and magnetic properties of profile samples were analyzed, and their relationship was examined, as well as the impact of climate change on fine-grained ferrimagnetic minerals and magnetic properties. The results revealed that red soils developed on weakly magnetic sandstone exhibited significant correlations between three magnetic indices, low-frequency magnetic susceptibility (χlf), frequency-dependent susceptibility (χfd), (χpost-pre + χd)/χpara, and the silica-sesquioxide ratio (SAF), indicating that these indices can be used to assess soil weathering. Additionally, this study proposed a new index based on the 1 < Log10Bh < 1.5 mT component obtained from decomposition of the IRM curve, which can also be used to assess soil weathering. The enhancement of magnetic properties in red soils along a single profile was found to be related to the increase in the content of fine-grained ferrimagnetic com-ponents controlled by weathering. Comparing the two climatic regions, it was found that in Yunnan, China, as the climate changes from subtropical humid to tropical humid, the weathering of the red soil profiles becomes stronger, and the fine-grained ferrimagnetic components increase, indirectly enhancing the magnetic properties of red soils. [ABSTRACT FROM AUTHOR]

Fe films with thicknesses between 17 and 95 nm were grown with a nano-sheet morphology, which enabled their high uniaxial magnetic, transport, and optical in-plane anisotropies. The top edge of the nano-sheets was directly visualized as nano-string-like structures of approximately 12.5–14 nm width and 100–300 nm length. The hysteresis loops showed a clear easy direction of magnetization in the longitudinal direction of the nano-sheets, whereas the hard direction loops were anhysteretic, with no remanence and zero coercive field. The anisotropy field exhibited values between 70 and 111 kA/m depending on the thickness of the films, with the maximum value corresponding to a 34 nm thick sample. The resistance of the films was also found to be highly anisotropic. The ratio (R⊥–R||)/R|| was ≈86%, with R|| and R⊥ being the resistances in the parallel and perpendicular directions of the nano-sheets, respectively. Likewise, the reflectivity of the samples behaved anisotropically; the ratio (IReflmax–IReflmin)/IReflmax of the intensity of reflected light by the films reached up to 61% for 34 nm thick samples, achieving the maximum value, IReflmax, when the plane of the incident light coincided with the direction of the nano-sheets and the minimum, IReflmin, when this plane was perpendicular to the direction of the nano-sheets. The origin of these anisotropic behaviors was established. These anisotropic films with high magnetization and high uniaxial anisotropies at the nanoscale can be useful for microelectronics applications, for devices such as magnetic sensors and transducers, or for ultrahigh frequency inductors. [ABSTRACT FROM AUTHOR]

Anisotropic bulk magnets of ThMn12-type SmFe10V2 with a high coercivity (Hc) were successfully fabricated. Powders with varying particle sizes were prepared using the ball milling process, where the particle size was controlled with milling time. A decrease in Hc occurred in the heat-treated bulk pressed from large-sized powders, while heavy oxidation excessively occurred in small powders, leading to the decomposition of the SmFe10V2 (1–12) phase. The highest Hc of 8.9 kOe was achieved with powders ball-milled for 5 h due to the formation of the grain boundary phase. To improve the maximum energy product ((BH)max), which is only 2.15 MGOe in the isotropic bulk, anisotropic bulks were prepared using the same powders. The easy alignment direction, confirmed by XRD and EBSD measurements, was <002>. Significant enhancements were observed, with saturation magnetization (Ms) increasing from 59 to 79 emu/g and a remanence ratio (Mr/Ms) of 83.7%. (BH)max reaching 7.85 MGOe. For further improvement of magnetic properties, controlling oxidation is essential to form a uniform grain boundary phase and achieve perfect alignment with small grain size. [ABSTRACT FROM AUTHOR]

Iron‐rich 2:17‐type SmCo magnets are expected to achieve high performance and relatively low cost. However, inhomogeneous cellular structures usually exist in iron‐rich magnets, resulting in a drastic reduction in coercivity and energy product. Herein, a strategy is proposed to regulate the dislocation by decreasing the Sm content and extending the solid‐solution duration in precursor of iron‐rich SmCo magnet. High‐density dislocations in precursor contributed to 1:5H nucleation, leading to uniform cellular structures in final magnets. As a result, a remarkable intrinsic coercivity of 1.50 T and one of the highest remanences (1.24 T) are simultaneously achieved in the iron‐rich Sm25Co42Fe26Cu5Zr2 (wt%) magnet. This study provides valuable insights into the design and development of iron‐rich 2:17‐type SmCo magnets. [ABSTRACT FROM AUTHOR]

We present new results of geochronological, rock magnetic, paleomagnetic and paleointensity studies of the olivine gabbro dyke located at the northern part of the Murmansk craton, NE Fennoscandia (the Kola Peninsula). According to its geochemistry, petrographic and geochronology features, the dyke belongs to the 2.68 Ga dyke swarm, as confirmed by Sm-Nd mineral isochron. We find a significant difference in the rock magnetic and paleomagnetic characteristics of the central and marginal parts of the dyke, which is independently supported by petrography and geochemistry. It is shown that the rocks of the central part of the dyke retained not only their primary mineral composition, but also the primary component of the natural remanent magnetization. We use its direction to determine the 2.68 Ga virtual geomagnetic pole for the Murmansk craton: Slat = 68.64292° N, Slong = 37.7945° E, N = 41 specimens, Plat = –73.5°, Plong = 138.9°, dp/dm = 3.2°/3.4°, paleolat = –65.9°. We also obtain reliable estimates (17 samples) of the Earth's magnetic field intensity at ca. 2.68 Ga: VDM value is found to be 1.85 × 1022 A m2 corresponding to the geomagnetic field several times weaker than the present-day field. [ABSTRACT FROM AUTHOR]

Abstract—The paper presents the results of rock magnetic studies and relative paleointensity determinations from sediments of Lake Shira, Khakassia. Carrier minerals of natural remanent magnetization (NRM) were identified through hysteresis loop parameter measurements, thermomagnetic and X-ray diffraction (XRD) analyses. The sediment age was determined by radiocarbon dating; according to age estimates, the studied sediment sequence covers approximately the past 9100 years. To obtain high-quality relative paleointensity results, the determinations were made on linear segments of the pseudo-Arai‒Nagata diagrams. The quality was assessed by the criteria of the number of points in the calculations of slope, quality criterion (q), NRM fraction destroyed in the paleointensity determination interval, and relative paleointensity determination error (σ). According to the rock magnetic studies and XRD analysis, the magnetic carriers are mainly single-domain (SD) and pseudo-single-domain (PSD) magnetite and hematite. The comparison of the obtained relative paleointensity data with model paleointensities calculated for the Shira coordinates from the various models (CALS10K.1b (Korte et al., 2011), PFM9k.1 (Nilsson et al., 2014), HFM.OL1.AL1, CALS10k.2 ARCH10k.1 (Constable et al., 2016)), with absolute paleointensities and with the collection of results from the studies of sedimentary and igneous rocks and archaeomagnetic objects has shown that these data are in good agreement and share common trends. This provides grounds for applying this approach to paleointensity determination from bottom sediments of modern lakes using the pseudo-Thellier method. [ABSTRACT FROM AUTHOR]

Abstract—A collection of igneous rocks of the Ukrainian Shield sampled from the Korsun-Novomyrhorod pluton (age interval 1760–1735 Ma, Ingul Domain) and from the Korosten pluton (age 1760–1750 Ma, North-Western Domain) is studied. The magnetic and thermomagnetic properties of samples were studied and X-ray diffraction analyses were carried out to obtain reliable determinations of paleointensity (Banc), It is shown that the carriers of the characteristic component of natural remanent magnetization are single- and small pseudo-single-domain magnetite grains. Banc was determined by two methods: through the Thellier‒Coe procedure with pTRM checks and by Wilson method. Paleointensity determinations are obtained from five sites and shown to meet quality criteria. For all sites, Banc and the virtual dipole moment (VDM) values are extremely low, varying within the ranges 3.6–9.76 μT and (0.92–2.43) × 1022 Am2, respectively. The analysis of the data from the paleointensity world database (WDB) indicates that the geodynamo operation mode in the Proterozoic can be characterized by an alternation of strong and weak dipole regimes, but the validity of this conclusion entirely depends on the reliability of data reported in the literature and presented in the WDB. [ABSTRACT FROM AUTHOR]

Abstract—The collection of paleomagnetic samples of the Lower Devonian Frænkelryggen Formation from the northwest of Spitsbergen is studied. The main carrier of the natural remanent magnetization of the studied rocks is hematite. Based on the component analysis results, the prefolding, bipolar components of the natural remanent magnetization with a positive reversal test are identified. The sequence of the magnetozones of the studied section is compared with the existing world data for Lower Devonian. [ABSTRACT FROM AUTHOR]

• A compact magnetic structure for rotary magnetic regenerators is designed. • A parametric set of simulations is performed to enhance the magnet shape. • Magnet shape strongly impacts the cooling capacity of magnetic refrigerators up to 40%. • Proposed solutions maximize the field up to 19% and minimize the magnet volume up to 44%. • Presented solutions outperform existing magnetic structures for rotary devices. A magnetic structure intended for use in a room-temperature rotary active magnetic regenerator (AMR) is presented, under construction at the University of Genoa. Given the overall size of the regenerator and the thickness of the gap, the magnet design is optimized to produce the highest possible magnetic field difference between two adjacent regions. Magnet shape optimization is obtained by introducing a geometry with four degrees of freedom corresponding to the position of the edges of each magnet, plus the remanence angle. This approach serves two main purposes: the primary is to increase the magnetic induction and, to follow, some effort is made to minimize the volume and weight of the expensive NdFeB magnets, while preserving the cooling performance. So, a balance between these two goals must be achieved. After a rough preliminary sizing, a parametric investigation is performed toward these targets and some shapes are presented. The magnetic flux density in the gap, and other consolidated and novel performance indices, are evaluated and compared to those found in the literature for similar devices. The final design achieves, in the air gap, a maximum induction value of 1.045 T, and an average flux density of 0.83 T in a volume per unit length of 0.00268 m3/m in the high induction region. This is accomplished by using 0.00606 m3/m of magnetic material (N50, NdFeB). The magnet designs presented here exhibit a well-balanced performance (in terms of greater cooling for the same magnet weight) compared to earlier designs for similar AMR devices. [ABSTRACT FROM AUTHOR]

The Clarion–Clipperton Fracture Zone (CCFZ) in the eastern central Pacific Ocean is the world's largest area for potential deep‐sea polymetallic nodule mining and is attracting increased scientific and commercial interest. Recent studies indicate that biogenic magnetite, generated intracellularly by magnetotactic bacteria (MTB), can carry a biogeochemical remanent magnetization in polymetallic nodules, although whether biogenic or physical‐chemical processes are responsible for nodule formation remain poorly constrained. Here, we report a combination of magnetic, electron microscope and geochemical analyses on seafloor surface sediments from the eastern CCFZ to understand the spatial distribution of biogenic magnetite and possible relationships between MTB and polymetallic nodules. Experimental results indicate that sedimentary magnetic minerals from the northern and southern regions are dominated by detrital (eolian loess and volcanic material) and biogenic magnetic minerals (magnetosomes), respectively. Sediments from the intermediate region contain both detrital and biogenic magnetic minerals. Quantitative first‐order reversal curve‐principal component analysis indicates that biogenic magnetite has the highest concentration in the intermediate CCFZ region, coincident with the highest polymetallic nodule density. Combined with previous research, we speculate that MTB growth on the CCFZ seafloor is driven mainly by local redox conditions. Manganese nodule surfaces are rich in organic biofilms, which results in a relatively thick oxic‐anoxic transition zone in high‐abundance manganese nodule regions, which generates an optimal microenvironment for both MTB growth and magnetite biomineralization. This study provides new clues for understanding the ecological distribution of MTB and the biogeochemical remanent magnetization recorded by biogenic magnetite in deep‐sea sediments. Plain Language Summary: Polymetallic nodules are an important seafloor resource because they contain economically important minerals (e.g., Ni, Co, and Mn) that are not common on land. Hence, there is increased economic and scientific interest in understanding the formation mechanisms of these materials. Several studies indicate that biogenic magnetite crystals produced by magnetotactic bacteria (MTB) occur within polymetallic nodules. Testing the relationship between MTB abundance and polymetallic nodule distribution can help to better understand how these materials formed. Here, we study seafloor sediments from the Clarion‐Clipperton Fracture Zone (CCFZ) and find that they mainly contain biogenic and detrital magnetic minerals. Detrital magnetic minerals come from volcanic chains and eolian dust, while biogenic magnetite forms within bacterial cells. We find that increased biogenic magnetite abundance coincides with higher polymetallic nodule occurrences in the CCFZ. This implies that MTB activity may play a significant role in the formation and growth of polymetallic nodules. Key Points: Biogenic and detrital magnetic minerals are quantified in seafloor surface sediments from the Clarion–Clipperton Fracture ZoneBiogenic magnetite concentrations and polymetallic nodule density are increased in the central Clarion–Clipperton Fracture ZonePolymetallic nodule growth likely produced reducing, organic‐rich microenvironments suitable for magnetotactic bacteria [ABSTRACT FROM AUTHOR]