Isothermal Magnetization Research Articles

Dimensional crossover from 3D to 2D and critical properties in the Laves phase HoNi2

ABSTRACT The critical exponents of the HoNi2 intermetallic alloy have been precisely obtained from the modified Arrott plots and the Kouvel-Fisher method, with values: β = 0.215, γ = 0.748, and δ = 4.489. With these values of the critical exponents, the isothermal magnetization M (μ0H) curves collapse below and above the Curie temperature (T C = 14 K) into two universal branches, fulfilling the single scaling equation m = f ± ( h ) , where m and h are the normalized magnetization and normalized magnetic field, respectively. The reliability of the critical exponents was confirmed by the Widom scaling hypothesis δ = 1 + γ / β , indicating that they are unambiguous and intrinsic to HoNi2 compound. This set of critical exponents lies between the theoretical values predicted by 3D and 2D models, suggesting a dimensional crossover between them. The primary reason for the nature of the determined critical behavior is linked to the tetrahedral local environment of Ni atoms within the unit cell.

Linearity of natural versus laboratory-imparted remanence demagnetization diagram and reliability of relative paleointensity estimation

Information on geomagnetic field intensity in the past is essential for understanding the behavior and mechanism of the geodynamo. A fundamental unresolved problem of relative paleointensity (RPI) estimations from marine sediments is that changes in the constituents of magnetic mineral assemblages may influence RPI estimations, called lithological contamination. A negative correlation between RPI and the ratio of anhysteretic remanent magnetization (ARM) susceptibility to saturation isothermal remanent magnetization (kARM/SIRM), which is a proxy for the proportion of magnetofossils to detrital magnetic minerals, was previously reported from deep-sea sediments. This could be caused by lower RPI recording efficiency of the magnetofossil component than the detrital component. To elaborate further this issue, we have conducted a paleo- and rock magnetic study of a sediment core taken from the central north Pacific. RPI estimated from a slope in a diagram plotting a pair of natural remanent magnetization (NRM) and ARM at each alternating-field demagnetization step (NRM-ARM demagnetization diagram) has a negative correlation with kARM/SIRM. Principal component analysis of first-order reversal curve diagrams indicates a downcore increase of the magnetofossil proportion with increased kARM/SIRM. These results reinforce the lower RPI recording efficiency of magnetofossils. In this core, the magnetic coercivity ranges of the magnetofossil and detrital components overlap, which produces a linear NRM-ARM demagnetization diagram. This hinders a possibility of obtaining uncontaminated RPI from a coercivity window representing the magnetofossils or detrital magnetic components, which was tried by some previous studies. A linear NRM-ARM demagnetization diagram, which was sometimes used as a criterion of reliable RPI estimations, does not necessarily mean the absence of lithological contamination to the RPI. In sediments with changing proportion of magnetofossils, normalization with IRM may work better than ARM.Graphical

Unveiling A-site substituent’s influence on magnetocaloric response in La2-xNaxNiMnO6 (0.0 ≤ x ≤ 1.0) double perovskite manganite materials

Abstract In this study, the compounds of La2-xNaxNiMnO6 (x = 0.0, 0.1, 0.2, 0.3, 0.5, and 1.0) double perovskite manganites have been produced by employing the sol-gel method to investigate their magnetocaloric effect. From X-Ray Diffraction analysis, all compounds crystallized in rhombohedral structure form with the $${\rm{R}}\bar{3}{\rm{c}}$$ R 3 ¯ c space group confirmed using the Rietveld refinement technique. The compounds show a magnetic phase transition from ferromagnetic to paramagnetic according to the temperature-dependent magnetization measurement. The phase transition temperatures sharply increased with Na doping (x = 0.1) to 277.8 K which can be considered as under room temperature level and then slowly decreased with further Na concentration to 262.3 K. Using an external magnetic field-dependent magnetization measurements, the isothermal magnetization curves were obtained, and these curves used to find the magnetic entropy change values, which give info about compounds’ characteristics of magnetic cooling performance. Under 5 T magnetic field change, the maximum magnetic entropy change value increased 10 times with a small amount of Na doping (x = 0.1), and compounds’ values changed from 0.21 to 1.29 Jkg−1K−1 for x = 0.0 to 1.0 compounds, respectively. Arrott plots were graphed by using isothermal magnetization curves to demonstrate all the compounds have a 2nd order magnetic phase transition which supports that these compounds can be candidates as magnetic refrigerants. Graphical Abstract

Non-equilibrium Spin Dynamics of the Frustrated Trication Spinel ZnMnCoO4in the Hierarchical Free-energy Framework.

Short-range spin correlations, memory and rejuvenation effects have been reported in the trication oxispinel ZnMnCoO4whose low-temperature spin dynamics, triggered by magnetic frustration (fr~ 6), could be better explained by the 'phenomenological' hierarchical spin-glass model than the short-range droplet theory. Accordingly, the aging mechanism of the system had an asymmetric memory response to the positive and negative thermal cycles within the cluster-glass state (~ 32.6 K), demonstrated a hierarchical organization of the phase space where its metastable energy states undergo continuous splitting with decreasing temperature. An attempt to reproduce the time evolution of the isothermal remanent magnetization in the system led to an investigation of various relaxation models featuring semi-logarithmic, algebraic, fractional or stretched-exponential tails. Nevertheless, Weron's probabilistic relaxation model (here, the fractal character β ~ 0.4, the hierarchical constraint k > 0, and the order parameterq(T ~ 0.12TSG) = 1.88) based on a purely stochastic approach, was best suited for understanding the slow spin dynamics of the cluster-glass phase in the entire temporal range. A comprehensive picture of the magnetic phase map was developed for the system, aided by magnetometry techniques and heat-capacity studies.

Magnetic Properties Change in Street Dust in Baghdad City, Iraq

The magnetic properties of street dust in the north and south of Baghdad, Iraq, have been studied. Fifty soil samples have been collected from heavily Traffic streets. Mass-specific magnetic susceptibility (χ), frequency-dependent susceptibility (χfd%), anhysteretic remanent magnetization (χarm), saturation isothermal remanent magnetization (SIRM), and thermomagnetic analyses were investigated. Mass-specific magnetic susceptibility (χ) is 72.86 × 10-8 m3kg-1 and 98.31 × 10-8 m3kg-1 for northern Baghdad (BN) and southern Baghdad (BR) (mean values), respectively. χ is well correlated with χarm with correlation coefficients (R2) of 0.96 and 0.83 for BN and BR, respectively. Grain size analyses show the existence of single-domain (SD) magnetite and maybe a small portion or absence of superparamagnetic (SP) grains in the samples. Thermomagnetic analyses clearly show a dramatic drop in the curve around 580°C during heating, which is the Curie temperature of magnetite. Results of concentration-dependent parameters, grain size, coercivity, and thermomagnetic analyses show the dominance of a soft magnetic phase like magnetite and the existence of a hard magnetic phase like hematite or goethite.

Study of magnetic and magnetocaloric properties of FeMnO3 compound

Abstract The study reports a magnetocaloric effect (MCE) in the FeMnO3 bixbyite compound prepared via autocombustion technique using nitrate salts. The X-ray diffraction (XRD) study showed that FeMnO3 assumes a cubic phase with a space group Ia-3. X-ray photoelectron spectroscopy (XPS) study confirmed the oxidation states of Fe3+ and Mn3+. Temperature-dependent magnetization measurements revealed the presence of antiferromagnetic ordering in the compound at around 40 K. The effective magnetic moment, µ eff, was calculated as 2.36 µB from the susceptibility curve. Change in maximum magnetic entropy ǀ∆S Max ǀ, determined from magnetic isotherms, is approximately 4.14 Jkg−1 K−1 at 65 K under 5 T applied field, leading to higher relative cooling power, RCP as 200.29 Jkg−1. Specific heat capacity, ∆Cp, and temperature-averaged entropy change, TEC, were also analyzed to study magnetic cooling efficiency. This study observed that FeMnO3 displays potential MCE performance, making it a promising candidate for magnetic refrigeration applications. Graphical abstract

Crystal Structure and Magnetic Properties of the Novel Compound ErMn5Ge3.

The RE-M-Ge systems (RE: rare earths, M: transition group elements) contain a large number of compounds with special magnetic properties. A novel compound ErMn5Ge3 was found during the investigation on the phase diagram of the Er-Mn-Ge ternary system, and its crystal structure and magnetic properties were investigated. Powder X-ray diffraction results show that ErMn5Ge3 crystallizes in an orthorhombic YNi5Si3-type structure with the space group Pnma (No. 62) and the lattice parameters of a = 13.0524(6) Å, b = 3.8853(7) Å, and c = 11.4027(4) Å. The magnetization curves and isothermal magnetization curves from 100 to 300 K were measured for ErMn5Ge3. Magnetic tests showed that the compound was weakly magnetic and had a Curie temperature of 304 K. It is believed that its magnetic properties are determined by Mn atoms, which are surrounded by a complex environment, leading to uncertainty in the direction of the magnetic moment and hence poor magnetic ordering. This uncertainty simultaneously leads to a significant separation of the ZFC and FZ curves. First-principles calculations confirm that the magnetic properties of ErMn5Ge3 are mainly provided by the Mn atoms, and its magnetic moment is calculated to be about 4.5 μB. A possible magnetic structure model with simultaneous Mn-Mn ferromagnetic/antiferromagnetic coupling is constructed based on the Mn atom spacing, which can well explain the magnetic performance of ErMn5Ge3.

Investigation of magnetic and transport properties of GdSbSe.

We report the detailed investigation of the magnetic, transport, and magnetocaloric effects (MCEs) of GdSbSe by magnetic susceptibilityχ(T), isothermal magnetizationM(H), resistivityρ(T,H), and heat capacityCp(T)measurements, crystallizing in the ZrSiS-type tetragonal crystal system with space group P4/nmm. Temperature-dependent magnetic susceptibility measurements revealed long-range antiferromagnetic ordering with two additional magnetic anomalies below Néel temperature (TN≈8.6K), corroborated through magnetocaloric and specific heat studies. Isothermal magnetization measurements unveil hidden metamagnetic signatures through a clear deviation from linearity. In addition, the enhanced value of the Sommerfeld coefficient (γ= 152(5) mJ mol-1K2) suggests strong electronic correlations in GdSbSe. The entropy of magnetization derived from magnetic isotherms unfolds the field-induced transition from Inverse MCE to Conventional MCE. The detailed transport properties indicate a semimetallic behavior, strongly coupled with magnetic order. Furthermore, the linear field dependence of MR in the high-field region anticipate the possibility of Dirac-like dispersion. Deviations from Kohler's rule and non-linear Hall resistivity suggest the multiband nature of GdSbSe.

Phragmites australis elevated concentrations of soil-bound heavy metals and magnetic particles in a typical urban plateau lake wetland, China.

Vegetation change significantly altered the hydrological processes and soil erosion within riparian ecosystems. It is unclear how change in managed vegetation types affect the geochemical behavior of heavy metals (HMs) and magnetic particles in karst riparian areas. Two soil depths of 0-20cm and 20-40cm were taken in alien species Phragmites australis (P. australis), native species Juncus effuses and Schoenoplectus tabernaemontan in a typical urban plateau Lake wetland, Caohai lake, China. Low-frequency mass magnetic susceptibility (χLF), anhysteretic remanent susceptibility (χARM), isothermal remanent magnetization, Cd, Cr, Cu, Sb, Ni and Zn were determined. Compared with Juncus effuses and Schoenoplectus tabernaemontani, P. australis habitat had the higher values of HMs, χLF, χARM, and isothermal remanent magnetization in top-soils. Frequency-dependent magnetic susceptibility ranged from 4.84% to 10.87% in top-soils and 6.82%-9.95% in sub-soils, lithogenic/pedogenic factors mainly masked the contribution of anthropogenic factors to magnetic signal enhancement. The correlation between variations of Cu and Sb with χARM and isothermal remanent magnetization was found to be significant in top-soils, but not in sub-soils. P. australis tended to promote the enrichment of HMs and enhancement of magnetic signal, the impact of P. australis expansion on the distribution of soil HMs and magnetic particles in Caohai riparian wetland should be not disregarded.

Exploring Structural, Magnetic, and Electric Transport Properties of Sol–Gel Derived Nd0.65Ca0.35MnO3

This paper investigates the phase separation phenomena in low bandwidth manganites, such as Nd1-xCaxMnO3, focusing on the nanoscale effects. Specifically, it aims to understand the competing phase tendencies concerning particle size in the prototypical phase‐separated compound Nd0.65Ca0.35MnO3 (NCMO). Nanosized material was synthesized through sintering sol–gel derived powders at a temperature of 900°C. Using the Rietveld refinement technique, the structure of the NCMO was investigated. It was found that NCMO has an orthorhombic shape with the Pnma spatial group. Mn2p and Mn2s core‐level X‐ray photoemission spectroscopy confirms that Mn has +3, +4 ions coexist in the intended ratio. The transition from paramagnetic (PM) to ferromagnetic (FM) states is shown by magnetization measurements performed at H = 100 Oe. Observations of note include the disparity between zero‐field cooled (ZFC) and field cooled warming (FCW) magnetization, indicating a glassy behavior at lower temperatures, and the hysteresis loop between cooling and warming cycle in the presence of field magnetization. Isothermal magnetization loop analysis confirms the dominance of the antiferromagnetic (AFM) component at higher magnetic fields. However, the resistivity versus temperature data does not reveal an insulator–metal transition (IMT). Instead, the PM state in the sample shows conduction via variable range hopping.

Spin Glass State and Griffiths Phase in van der Waals Ferromagnetic Material Fe5GeTe2.

The discovery of two-dimensional (2D) van der Waals ferromagnetic materials opens up new avenues for making devices with high information storage density, ultra-fast response, high integration, and low power consumption. Fe5GeTe2 has attracted much attention because of its ferromagnetic transition temperature near room temperature. However, the investigation of its phase transition is rare until now. Here, we have successfully synthesized a single crystal of the layered ferromagnet Fe5GeTe2 by chemical vapor phase transport, soon after characterized by X-ray diffraction (XRD), DC magnetization M(T), and isotherm magnetization M(H) measurements. A paramagnetic to ferromagnetic transition is observed at ≈302 K (TC) in the temperature dependence of the DC magnetic susceptibility of Fe5GeTe2. We found an unconventional potential spin glass state in the low-temperature regime that differs from the conventional spin glass states and Griffiths phase (GP) in the high-temperature regime. The physical mechanisms behind the potential spin glass state of Fe5GeTe2 at low temperatures and the Griffith phase at high temperatures need to be further investigated.

Size-fractionated carbonaceous and iron-rich particulate matter in urban environments of France and Senegal

Road traffic is one of the main sources of particulate matter in the urban environment, emitting particulate organic and elemental carbon compounds and metal-rich particles through combustion and brakes and tires wear. In Western Africa, the carbon and metal composition of airborne particles is also influenced by additional sources linked to biomass combustion and recent industrialization. Here, we investigated the impact of combustion-related and non-combustion-related emissions on the distribution of carbonaceous fractions and iron-rich particles in two urban environments in France and Senegal. The supermicron fraction (Da>1{1}$$\\end{document}]]>µm) showed a significantly higher isothermal remanent magnetization (SIRM) than finer fractions, accounting for 79% in France and 81% in Senegal of the total SIRM. In the submicron fraction (Da<1µm), we noted significantly higher concentrations of total carbon (TC) and elemental carbon (EC) than for other fractions, both accounting for 71% in France and 68% and 75% in Senegal of the total and elemental particulate carbon concentration, respectively. Electron microscope observations revealed the presence of iron-rich particles for Da<0.2µm, however, associated with a weak SIRM. Such iron particles may be produced by combustion or abrasion while we suspect that emissions by the abrasion process produce larger particles.

Quantum spin-liquid in Ba3CuSb2O9 epitaxial thin films

Hexagonal perovskite materials are emerging quantum spin liquid (QSL) systems providing a fertile ground to realize novel quantum phenomena. The epitaxially grown thin films of such materials offer a compelling approach to utilize exotic quantum phases for device applications with better control over the structure. We fabricate the intriguing QSL triple perovskite Ba3CuSb2O9epitaxially onto a MgO (100) substrate by pulsed laser deposition technique as well as in bulk form for comparison. The presence of only (00l) parallel planes of Ba3CuSb2O9in x-ray diffraction validates the epitaxial growth of the thin film. Temperature-dependent magnetization of thin film reveals no magnetic ordering down to 400 mK, with a large antiferromagnetic Curie-Weiss temperature (θCW≈-11.68 K). This indicates strong magnetic frustration and QSL behaviour, similar to bulk Ba3CuSb2O9. The presence of magnetic correlations at low temperature (in the quantum spin liquid state) is further confirmed by analysing the low temperature magnetic isotherms. These experimental findings underscore the potential of this quantum material for its use in quantum technologies.

Effect of Mn Doping on the Modulation of Magnetoelectric and Mechanical Properties of Cu–Ni–Sn Alloys

In this research, the magnetoelectric and mechanical properties of Cu77–xNi15Sn8Mnx (x = 0, 5, 10, 15, 20 at%) alloy are systematically studied. In the results, it is demonstrated that the magnetic properties of the alloy increase with an increase in the Mn content, as evidenced by the thermomagnetic curve and isothermal magnetization curve. The magnetic properties of the annealed Cu57Ni15Sn8Mn20 alloy reach about 15 emu g−1 at room temperature, and the Curie temperature (Tc) reaches about 360 K in a 1 k Oe magnetic field. The characteristic peak of the magnetic transition in the AC magnetic susceptibility test also corresponds to the Curie temperature. An electrical performance test calculated the resistivity of the alloy, the resistivity of Cu57Ni15Sn8Mn20 in its annealed state is about 26% lower than that of Cu77Ni15Sn8. Furthermore, the hardness test reveals that the Vickers hardness of the Cu57Ni15Sn8Mn20 alloy is about 246.2 HV, demonstrating its excellent mechanical properties. In the research, it is shown that the doping of Mn elements plays a crucial role in the magnetic properties of Cu–Ni–Sn alloys. By adjusting the content of the Mn element, the magnetic performance can be controlled. A valuable approach is provided for enhancing the performance of magnetic Cu alloys.

Paleomagnetic inclinations and relative paleointensity variations during the upper Aptian to middle Albian in Sergipe-Alagoas Basin, South Atlantic Ocean (NE Brazil)

Summary During the Jurassic and Early Cretaceous, Earth's magnetic field experienced a high frequency of polarity reversals. This hyperactivity period is followed by a ∼38 Myr prolonged period of stable normal polarity from the Aptian until the Santonian, known as the Cretaceous Normal Superchron (CNS; chron C34n, from 121.4 to 83.65 Ma). However, the CNS might have been characterized by more variability than previously thought, but the current databaseis uneven in its spatial and temporal distribution. In this study, we integrate paleomagnetic and biostratigraphic data from the SER-03 sedimentary core, drilled onshore in the Sergipe-Alagoas Basin, NE Brazilian margin, South Atlantic Ocean. The 183-meter cored interval spans 5.2 Myr (114.7–109.5 Ma), including the Aptian–Albian transition. It records the evolution from restricted marine settings to the complete opening of the South Atlantic Ocean. Magnetic remanence and rock magnetic parameters, such as magnetic susceptibility, anhysteretic remanent magnetization, and isothermal remanent magnetization, were measured. Rock magnetic analyses indicated that primary magnetizations were preserved throughout the interval, with detrital magnetite identified as the primary magnetic carrier, predominantly in the pseudo-single domain and low-coercivity states. Normalizations by χ, ARM15mT, and IRM15mT were used to determine relative paleointensity curves and were compared to the curve resulting from the pseudo-Thellier method. The SER-03 relative paleointensity record shows marked changes in both intensity and inclination. Inclination instability results are comparable with those found in volcanic rocks from surrounding the region. The high-resolution SER-03 magnetic record revealed that the field variability was higher than expected during the CNS, but remaining substantially lower than during other periods, such as thelate Jurassic. The new SER-03can serve as a dating and correlation tool for coeval records.

Simulation of zero field cooled/field cooled magnetization and isothermal magnetization curves of distributed nanoparticle assembly

Simulation of zero field cooled/field cooled magnetization and isothermal magnetization curves of distributed nanoparticle assembly

Magnetic property of CuTa2-xSbxO6

An insulating solid solution with the general formula CuTa2-xSbxO6and a limited range of homogeneity (0 ≤ x ≤ 0.5), synthesized in a high-temperature solid state reaction, was subjected to magnetic studies due to the presence of a temperature-independent contribution to the magnetic susceptibility. For this purpose, the magnetic susceptibility (χ) and the magnetic isotherm (M) were measured. From the temperature dependence of the χT product, the temperature independent Van Vleck\\s magnetic susceptibility, χ0, was estimated. This value was then subtracted from the measured magnetic susceptibility, χ, yielding the magnetic parameters of the solid solution, which were consistent with the tabulated values.

Thermodynamics and entropic inference of nanoscale magnetic structures in Gd

A bulk gadolinium (Gd) single crystal exhibits virtually zero remnant magnetization, a common trait among soft uniaxial ferromagnets. This characteristic is reflected in our magnetometry data showing virtually hysteresis free isothermal magnetization loops with large saturation magnetization. The absence of hysteresis allows to model the measured easy axis magnetization as a function of temperature and applied magnetic field, rather than a relation, which permits the application of Maxwell relations from equilibrium thermodynamics. Demagnetization effects broaden the isothermal first-order transition from negative to positive magnetization. By analyzing magnetization data within the coexistence regime, we deduce the isothermal entropy change and the field-induced heat capacity change. Comparing the numerically inferred heat capacity with relaxation calorimetric data confirms the applicability of the Maxwell relation. Analysis of the entropy in the mixed phase region suggests the presence of hitherto unresolved nanoscale magnetic structures in the demagnetized state of Gd. To support this prediction, Monte Carlo simulations of a 3D Ising model with dipolar interactions are performed. Analyzing the cluster size statistics and magnetization from the model provides strong qualitative support of our analytic approach.

Biomagnetic monitoring of the spatial distribution of atmospheric particulate matter in an industrialized city in Japan: Case study at Muroran

&lt;p&gt;Japan has 111 active volcanoes, supplying a great amount of magnetically-enhanced fly ashes. Such fly ashes likely mask anthropogenic magnetic signals; therefore, only a few magnetic biomonitoring studies have been reported in active volcanic regions, including Japan. The environmental magnetic results are reported for the materials deposited on Sasa Kurilensis, also known as dwarf bamboo, in the vicinity of the industrialized Muroran city center in Japan. The dust on the ten leaves at 105 sites was wiped off with a commercial wipe sheet, and their rock magnetic properties were analyzed. Room- and low-temperature magnetic analyses indicate that the major magnetic mineral in the dust is partially oxidized magnetite, ranging from single to pseudo single domain size, and the magnetic mineralogy on the leaves’ surface remains consistent throughout the study area. Much higher saturation isothermal remanent magnetization intensities are observed in the city’s eastern parts. The dominant wind directions in Muroran city are northwest, indicating that the steel companies in the city center are the major source of the fine-grained magnetic minerals on the dwarf bamboo leaves. These results indicate that using the leaves of dwarf bamboo for magnetic biomonitoring can be a non-destructive and rapid method to study the spatial distribution of atmospheric particulate matter from local industrial activities, even in active volcanic areas.&lt;strong&gt;&lt;/strong&gt;&lt;/p&gt;

Biomagnetic monitoring of the spatial distribution of atmospheric particulate matter in an industrialized city in Japan: Case study at Muroran

&lt;p&gt;Japan has 111 active volcanoes, supplying a great amount of magnetically-enhanced fly ashes. Such fly ashes likely mask anthropogenic magnetic signals; therefore, only a few magnetic biomonitoring studies have been reported in active volcanic regions, including Japan. The environmental magnetic results are reported for the materials deposited on Sasa Kurilensis, also known as dwarf bamboo, in the vicinity of the industrialized Muroran city center in Japan. The dust on the ten leaves at 105 sites was wiped off with a commercial wipe sheet, and their rock magnetic properties were analyzed. Room- and low-temperature magnetic analyses indicate that the major magnetic mineral in the dust is partially oxidized magnetite, ranging from single to pseudo single domain size, and the magnetic mineralogy on the leaves’ surface remains consistent throughout the study area. Much higher saturation isothermal remanent magnetization intensities are observed in the city’s eastern parts. The dominant wind directions in Muroran city are northwest, indicating that the steel companies in the city center are the major source of the fine-grained magnetic minerals on the dwarf bamboo leaves. These results indicate that using the leaves of dwarf bamboo for magnetic biomonitoring can be a non-destructive and rapid method to study the spatial distribution of atmospheric particulate matter from local industrial activities, even in active volcanic areas.&lt;strong&gt;&lt;/strong&gt;&lt;/p&gt;