Magnetic Impedance Research Articles

Magnetic Coupling-Based Battery Impedance Measurement Method

The battery impedance is an important indicator of battery health status. In this paper, a magnetic coupling-based impedance measurement method for electrochemical batteries is proposed. Without affecting the energy injection stage, the designed suppression resistance can minimize the influence of the primary circuit response, and the under-damped oscillation waveform containing the battery impedance information can be directly obtained on the primary inductance. The change of the mutual inductance value within a certain range will not affect the measurement results. Therefore, the measurement system has high stability and robustness. By utilizing the discrete Fourier transform (DFT)-based algorithm to calculate the damped oscillation parameters, the battery impedance is accurately derived from the calculated attenuation coefficient and damped oscillation frequency. The accuracy of this method under different coupling parameters is analyzed and verified by simulation and experiment on a Li-ion battery, which could be employed to estimate the state of charge (SOC).

Optimization of 2.45 GHz microwave coupling depending on axial magnetic field profiles and impedance transformer in electron cyclotron resonance ion source

The optimization of 2.45 GHz microwave coupling in an electron cyclotron resonance (ECR) ion source is investigated through experiments and full wave simulation studies. The axial magnetic field profile and an impedance transformer are the two major factors affecting the optimum power coupling. Experimental observations have shown that the beam current density increases when the two ECR zones are located in the plasma chamber and when the first ECR zone is close to the RF entrance. A coupling study with various magnetic field profiles finds that the gap distance between the RF window and first ECR zone and the effective ECR zone width determines the coupling efficiency. Optimum power coupling is obtained under the condition of an appropriately slight gap distance comparable to the half width of the effective ECR zone. The extracted beam current density increases when the second ECR zone becomes closer to the plasma grid. With the optimized axial magnetic field profile, impedance transformers are designed in consideration of reflection coefficient with respect to the plasma density. The performance of the impedance transformers is experimentally evaluated in terms of the efficiency (mA/W) with the findings consistent with the results of a simulation. The highest beam current density (∼165 mA/cm2) in these experiments is achieved with the optimized axial magnetic profile and the impedance transformer.

Ionic Conductivity of Na3Al2P3O12 Glass Electrolytes-Role of Charge Compensators.

In glasses, a sodium ion (Na+) is a significant mobile cation that takes up a dual role, that is, as a charge compensator and also as a network modifier. As a network modifier, Na+ cations modify the structural distributions and create nonbridging oxygens. As a charge compensator, Na+ cations provide imbalanced charge for oxygen that is linked between two network-forming tetrahedra. However, the factors controlling the mobility of Na+ ions in glasses, which in turn affects the ionic conductivity, remain unclear. In the current work, using high-fidelity experiments and atomistic simulations, we demonstrate that the ionic conductivity of the Na3Al2P3O12 (Si0) glass material is dependent not only on the concentration of Na+ charge carriers but also on the number of charge-compensated oxygens within its first coordination sphere. To investigate, we chose a series of glasses formulated by the substitution of Si for P in Si0 glass based on the hypothesis that Si substitution in the presence of Na+ cations increases the number of Si-O-Al bonds, which enhances the role of Na as a charge compensator. The structural and conductivity properties of bulk glass materials are evaluated by molecular dynamics (MD) simulations, magic angle spinning-nuclear magnetic resonance, Raman spectroscopy, and impedance spectroscopy. We observe that the increasing number of charge-imbalanced bridging oxygens (BOs) with the substitution of Si for P in Si0 glass enhances the ionic conductivity by an order of magnitude-from 3.7 × 10-8 S.cm-1 to 3.3 × 10-7 S.cm-1 at 100 °C. By rigorously quantifying the channel regions in the glass structure, using MD simulations, we demonstrate that the enhanced ionic conductivity can be attributed to the increased connectivity of Na-rich channels because of the increased charge-compensated BOs around the Na atoms. Overall, this study provides new insights for designing next-generation glass-based electrolytes with superior ionic conductivity for Na-ion batteries.

Invisibility Utilizing Huygens’ Metasurface Based on Mantle Cloak and Scattering Suppression Phenomen

This communication presents the design of a Huygens' metasurface (HMS) coating aiming to achieve strongly enhanced invisibility. An analytical formulation for obtaining the required electric surface admittance and magnetic surface impedance is presented. The proposed unit cell consists of a pair of split-rin resonators in the top layer and a metal capacitor in the bottom layer of the same substrate. The geometries are properly designed to provide the required electric surface admittance and magnetic surface impedance for maximum scattering reduction at the operational frequency of 4 GHz. The designed HMS is optimized to realize the required electric surface admittance and magnetic surface impedance for remarkable cloaking purposes. Scattering-cross section (SCS) of uncloaked and cloaked conducting cylinders is obtained with CST Microwave Studio simulation which matches the analytical results. The results show robust scattering reduction with considerable bandwidth for the covered cylinder by the HMS. Furthermore, the obtained results with HMS are compared with the results presented in the literature for cloaking with ordinary metasurface. This comparison emphasizes a much better cloaking performance of the HMS. Considerable cloaking obtained in this communication can be applied for invisibility purposes, sensing applications, antenna isolation, radiation blockage reduction in antennas, etc.

A green and high-yield route to recycle waste masks into CNTs/Ni hybrids via catalytic carbonization and their application for superior microwave absorption

With the worldwide pandemic of COVID-19, a tremendous amount of face masks have been consumed and discarded, resulting in serious environment pollution and infectious hazards. Herein a green and high-yield route has been developed to recycle waste masks (WMs) into CNTs/Ni hybrids via catalytic carbonization. Our results exhibited that the yield of carbon was as high as 64.4 g/100 g WMs. Furthermore, the as-fabricated CNTs/Ni hybrids were applied for microwave absorption, which displayed superior performances, including a strong reflection loss of -56.3 dB and an absorption bandwidth of 4.3 GHz with absorber thickness of only 2.0 mm. The mechanism was mainly ascribed to the favorable synergistic effects of CNTs and Ni on conduction and magnetic losses, dipolar polarization, interfacial polarization and impedance matching. Thus, this work provides an environmentally friendly, scalable and cost-effective strategy for recycling waste masks into high-valuable carbon nanomaterials, and exploits their potential application for microwave absorption.

Neural Network for Metal Detection Based on Magnetic Impedance Sensor.

The efficiency of the metal detection method using deep learning with data obtained from multiple magnetic impedance (MI) sensors was investigated. The MI sensor is a passive sensor that detects metal objects and magnetic field changes. However, when detecting a metal object, the amount of change in the magnetic field caused by the metal is small and unstable with noise. Consequently, there is a limit to the detectable distance. To effectively detect and analyze this distance, a method using deep learning was applied. The detection performances of a convolutional neural network (CNN) and a recurrent neural network (RNN) were compared from the data extracted from a self-impedance sensor. The RNN model showed better performance than the CNN model. However, in the shallow stage, the CNN model was superior compared to the RNN model. The performance of a deep-learning-based (DLB) metal detection network using multiple MI sensors was compared and analyzed. The network was detected using long short-term memory and CNN. The performance was compared according to the number of layers and the size of the metal sheet. The results are expected to contribute to sensor-based DLB detection technology.

A novel paper biosensor based on Fe3O4@SiO2–NH2 and MWCNTs for rapid detection of pseudorabies virus

In this study, a novel paper biosensor based on Fe3O4@SiO2–NH2 magnetic polymer microspheres and multi walled carbon nanotubes (MWCNTs) for rapid detection of pseudorabies virus (PRV) was first developed. Fe3O4@SiO2–NH2 were functionalized with PRV antibody and doped in cellulose nitrate paper to fabricate the magnetic paper biosensor with good magnetic response and biocompatibility. Using MWCNTs to build conductive network of sensors, PRV antigen binds specifically to the immunomagnetic microspheres on the sensor, and the resulting immune complex changes the magnetic domain structure of the sensor and the structural gap of MWCNTs, causing the magnetic property and impedance change. TEM and EDS characterization proved that the biosensor was successfully doped with Fe3O4@SiO2–NH2 and effectively recognized PRV. Under optimized conditions, the impedance variation was found to be linearly related to the logarithm value of PRV concentrations in the range of 10–1 mg ml−1, with the detection limit of 10 ng ml−1. This paper biosensor demonstrated advantages of portability, high sensitivity and specificity, providing a valuable method for early control of PRV.

A convolutional neural network algorithm for breast tumor detection with magnetic detection electrical impedance tomography.

Breast cancer is a malignant tumor disease for which early detection, diagnosis, and treatment are of paramount significance in prolonging the life of patients. Magnetic Detection Electrical Impedance Tomography (MDEIT) based on the Convolutional Neural Network (CNN), which aims to realize non-invasive, high resolution detection of breast tumors, is proposed. First, the MDEIT forward problem of the coronal and horizontal planes of the breast was simulated and solved using the Finite Element Method to obtain sample datasets of different lesions. Then, the CNN was built and trained to predict the conductivity distribution in different orientations of the breast model. Finally, noise and phantom experiments were performed in order to assess the anti-noise performance of the CNN algorithm and its feasibility of detecting breast tumors in practical applications. The simulation results showed that the reconstruction relative error with the CNN algorithm can be reduced to 10%, in comparison with the truncated singular value decomposition algorithm and back propagation algorithm. The CNN algorithm had better stability in the anti-noise performance test. When the noise of 60 dB was added, the shape of the breast tumor could still be restored by the CNN algorithm. The phantom experimental results showed that through the CNN based reconstruction algorithm, the reconstruction conductivity distribution image was legible and the position of the breast tumor could be determined. It is reasonable to conclude that the MDEIT reconstruction method proposed in this study has practical importance for the early and non-invasive detection of breast tumors.

Controllable preparation and microwave absorption properties of shape anisotropic Fe3O4 nanobelts

To substantially prevent electromagnetic threatens, microwave absorbing materials (MAMs) are required to eliminate surplus electromagnetic waves. As a typical MAM, Fe3O4 particles with complex permittivity and permeability have been widely applied due to the coexistence of magnetic loss and dielectric loss. However, the necessary high mass fraction significantly limited its applications, thus Fe3O4 nanostructures have been extensively investigated to overcome this problem. In this work, uniform Fe3O4 nanobelts were prepared by electrospinning and two-step thermal treatment. By controlling the composition and viscosity of the electrospinning precursor solution, Fe3O4 nanobelts with tunable lateral sizes (200 nm–1 μm) were obtained. The samples with low content (only 16.7 wt%) Fe3O4 exhibited wide maximum effective absorbing bandwidths (EAB) over 3 GHz, and Fe3O4 nanobelts with smaller lateral sizes showed a maximum EAB of 4.93 GHz. Meanwhile, Fe3O4 nanobelts with smaller lateral sizes presented superior reflection loss properties, the lowest reflection loss reached −53.93 dB at 10.10 GHz, while the maximum EAB was up to 2.98 GHz. The excellent microwave reflection loss of Fe3O4 nanobelts was contributed to the enhanced synergistic effect of magnetic loss, dielectric loss, and impedance matching, originated from the hierarchically cross-linked networks and shape anisotropies. This study could broaden the practical applications of magnetic absorbers, and provided an approach for the development of shape anisotropic magnetic materials.

Ionic Mobility in Ion-Exchange Membranes.

Membrane technologies are widely demanded in a number of modern industries. Ion-exchange membranes are one of the most widespread and demanded types of membranes. Their main task is the selective transfer of certain ions and prevention of transfer of other ions or molecules, and the most important characteristics are ionic conductivity and selectivity of transfer processes. Both parameters are determined by ionic and molecular mobility in membranes. To study this mobility, the main techniques used are nuclear magnetic resonance and impedance spectroscopy. In this comprehensive review, mechanisms of transfer processes in various ion-exchange membranes, including homogeneous, heterogeneous, and hybrid ones, are discussed. Correlations of structures of ion-exchange membranes and their hydration with ion transport mechanisms are also reviewed. The features of proton transfer, which plays a decisive role in the membrane used in fuel cells and electrolyzers, are highlighted. These devices largely determine development of hydrogen energy in the modern world. The features of ion transfer in heterogeneous and hybrid membranes with inorganic nanoparticles are also discussed.

Characterizing the performance of eddy current probes using photoinductive field-mapping: a numerical approach

Nondestructive evaluation (NDE) method has been applied to analyze the configura- tions of coil probes and the characteristics of discontinuities in the few years, especially the ef- fects of probe tilt are paid attention to gradually. However, the probe tilt has been recognized as the one reason of producing noise in eddy current testing (ECT), such as the flaw manual scan- ning or the manufacture of probes with the irregular orientation coil. The inability to calibrate the tilt coil of probe makes it impossible to accurately inspect the surface cracks. Based on the above, we should found the applicable method to examine the structures of probe and demonstrate that it has the feasibility on investigating of probe with tilted coil. The photoinductive (PI) method is a novel inspection technique for detecting surface cracks. This paper shows how the PI technique can be utilized to analyze the effects of tilted coil of probe. The numerical multiphysics simula- tions of the PI imaging was performed with two dimensional finite element method (2D FEM) to characterize the variations of magnetic field and probe's impedance on a conductive metal foil. As anticipated, the proposed model shows that the PI imaging signals can reveal the construction of the probe. The FEM simulation results of tilted coils are showed and discussed. The effects of PI signals with different excited frequencies of the coil are also examined and analyzed. The simulation results demonstrate that not only the PI method is appropriate for investigating the structures of probe, but also how the tilt probe can affect the reliability of an eddy current in- spection.

Core/Shell Structured Ni/Fe3O4 Composites with Enhanced Electromagnetic Absorption Performances

Core/shell structured Ni/Fe3O4 composites with grain sizes of 200–800 nm were synthesized by using a hydrothermal method. The phase structure, morphology, magnetic and electromagnetic absorption properties of the as-prepared samples were characterized by various analysis techniques. Experimental results revealed that spinel Fe3O4 was in situ deposition on the surface of Ni spheres through electrostatic interactions. Moreover, the Ni/Fe3O4 mass ratios had a significant influence on the electromagnetic absorption performances. When the mass ratio of Ni/Fe3O4 was 1:1, the composites reached an outstanding reflection loss (RL) of [Formula: see text]48.06[Formula: see text]dB at 12.96[Formula: see text]GHz with a thin thickness of 1.8[Formula: see text]mm. Meanwhile, the effective absorption bandwidth was 5.36[Formula: see text]GHz (10.72–16.08[Formula: see text]GHz), covering the X and Ku bands. The enhanced electromagnetic absorption performance of core/shell structured Ni/Fe3O4 composites as compared to pure Ni, may be attributed to the multiple interfacial polarization, magnetic exchange coupling resonance and optimal impedance matching. Consequently, core/shell structured Ni/Fe3O4 composites would be promising candidates for a wider range of electromagnetic absorption applications.

Improved magnetic loss and impedance matching of the FeNi-decorated Ti3C2Tx MXene composite toward the broadband microwave absorption performance

MXene-based magnetic–dielectric composites with synergetic magnetic and dielectric losses have exhibited great potential in the practical applications of microwave absorbing material. In the present paper, novel composites consisting of laminated Ti3C2Tx MXene decorated with magnetic FeNi nanoparticles were constructed via a facile in situ hydrothermal approach. The microstructure, morphology, magnetic properties, and microwave absorption performances of as-synthesized samples were investigated in detail, and corresponding mechanisms were further discussed. Results demonstrated that the frequency dependence of electromagnetic parameters for the FeNi/Ti3C2Tx MXene composites could be easily regulated by simply changing the content of FeNi nanoparticles in favor of improved magnetic loss and optimized impedance matching. Consequently, a broadband effective absorption bandwidth (RL < − 10 dB) of 6.2 GHz with a thin matched thickness of 1.6 mm was achieved for the FeNi/Ti3C2Tx MXene composites with 20 wt% FeNi loading, which could be identified as high-efficiency microwave absorbing material.

Myocardial tissue characterization and mortality in transcatheter aortic valve replacement

Abstract Background Cardiac decompensation in severe aortic stenosis involves accumulation of myocardial extracellular matrix and congestion, which can be objectively quantified by cardiac magnetic resonance (CMR) and bioelectrical impedance spectroscopy (BIS). The aim of this study was to determine whether the extent of extracellular matrix pre-intervention correlates with congestion and is associated with adverse outcomes. Methods Consecutive patients scheduled for transcatheter aortic valve replacement (TAVR) underwent assessment of volume status using BIS, and CMR, and were prospectively followed. CMR included T1 mapping and extracellular volume (ECV) quantification for the assessement of diffuse myocardial tissue alterations and T2 mapping (n=100) for the assessment of myocardial edema. The combination of all-cause death and heart failure (HF) hospitalization was selected as primary study endpoint. Results 180 patients (80.6±7.2 y/o, 48.9% female) with valid BIS and CMR data were included. ECV levels≥median was linked to worse ventricular function, more severe pulmonary hypertension and mitral/tricuspid regurgitation (p for all&amp;lt;0.05). Fluid levels significantly correlated with ECV (r=0.403, p&amp;lt;0.001) and T2 (r=0.378, p=0.015), but not T1 relaxation times (p&amp;gt;0.05). Moreover, fluid levels were independently associated with CMR-ECV by multivariate linear regression analysis (p&amp;lt;0.001), alongside with body mass index, left ventricular ejection fraction and hematocrit (p for all&amp;lt;0.05). In total, 22.9% (39/170) had experienced an event (22 deaths, 17 heart failure) 13.4±7.5 months following TAVR. ECV levels≥median of 27.0% were significantly associated with the combined endpoint by Kaplan Meier estimates (log rank, p&amp;lt;0.001, Figure 1), but also with HF hospitalization (p&amp;lt;0.001) and death (p=0.020), when analyzed separately. Quantitively, every 1% increase in ECV increased event hazard by 11% [hazard ratio 1.111, 95% confidence interval 1.030–1.198, p=0.007]. After multivariate adjustment for important clinical, laboratory and CMR parameters, ECV≥median remained independently associated with outcome (p=0.045), alongside with serum albumin (p&amp;lt;0.001) and body fluid levels (p=0.015) by Cox regression analysis. Conclusions Cardiac decompensation in AS involves myocardial ECV expansion and body fluid accumulation. Fluid accumulation seems to impact the amount of ECV, and both parameters are independently associated with adverse outcomes following TAVR. Figure 1 Funding Acknowledgement Type of funding source: Public grant(s) – National budget only. Main funding source(s): Österreichische Kardiologische Gesellschaft

Magnetic Properties and High-Frequency Impedance of Nanocrystalline FeSiBNbCu Ribbons in a 300 to 723 K Temperature Range

Magnetic properties and high-frequency impedance of nanocrystalline Fe73.5Si16.5B6Nb3Cu1 ribbons are studied in a high-temperature range of 300 to 723 K. The exchange-coupled state of nanocrystallites was found to be destructed at a temperature of about 530 K, which is substantially lower than the Curie temperature of the amorphous phase that is close to 635 K. It was found that, at an ac frequency of above 5 MHz, the marked magnetoimpedance effect (more than 50% for the magneoimpedance ratio in the case of complete impedance) is observed over the whole temperature range under study. This similar behavior can be essential in designing special-purpose magnetic field sensors intended for high-temperature applications.

Structure, Magnetic Properties and Magnetic Impedance of Fast Quenched Ribbons of Alloys Based on FINEMET in the Initial State and After Heat Treatment

Abstract–The effect of heat treatment (HT) on the structural features, magnetic properties, and magnetic impedance of rapidly quenched Fe73.5Si13.5B9Nb3Cu1 ribbons and doped ribbons, in which 10 wt % iron is replaced by either cobalt, nickel, or manganese, is studied in this paper. Cobalt ribbons as a result of HT at a constant temperature showed a significant increase in the value of maximum magnetic induction. The magnetic and magnetic-impedance properties, studied in a wide range of alternating current frequencies from 1 to 400 MHz, showed a significant change in the features of effective magnetic anisotropy and high-frequency responses after HT. A comparative analysis of the results obtained for samples of various compositions can be useful both for understanding the features of the formation of effective magnetic anisotropy in nanocrystalline alloys and from the point of view of practical applications in the search for optimal physicochemical parameters of materials for sensors of low magnetic fields.

Enhanced electromagnetic microwave absorption of Fe/C/SiCN composite ceramics targeting in integrated structure and function

The Fe/C/SiCN composite ceramics were synthesized by polymer-derived method to obtain the integration of structure and functions. The electromagnetic waves (EMW) absorption properties at X and Ku bands were investigated. The addition of nano-sized Fe particles improved the magnetic loss and impedance matching, and the carbon nanotubes generated by the iron in-situ catalysis increased the internal relaxation polarization and interfacial polarization, which together improved the EMW absorption properties significantly. In particular, the Fe/C/SiCN-9 showed the optimum reflection loss (RL) of −31.06 dB at 10.03 GHz with an effective absorption bandwidth (EAB, RL < −10 dB) of 3.03 GHz at 2.51 mm, indicating the excellent EMW absorption properties of Fe/C/SiCN composite ceramics.

Aluminum Ion Species Transport in Pure and Additive Modulated Deep Eutectic Solvents (DES) Electrolytes

The need for safe, low cost, high energy and density storage devices is ubiquitous the world over. Satisfying this need requires various energy storage and conversion applications, one of which is the aluminum ion batteries. One problem with expansion in their development and commercialization is the availability of optimized electrolytes. Recently, deep eutectic solvents (DES) have gained attention as electrolytes for energy storage devices. These solvents are similar to ionic liquids, but are generally cheaper and easier to prepare. Additionally, they are known to dissolve metal oxides which plague AIBs operation, and their solubility is dependent on the hydrogen bond donor. Because of their inherent tunability, we studied the effect of AlCl3 concentration (1:1 – 1.7:1 molar ratio), amide type (acetamide (AA), butyramide (BA), propionamide (PA)), viscosity reducing additive type and concentration, on the aluminum ion species and transport in AlCl3:amide DES electrolytes using multi-Nuclear (1H, 27Al) Magnetic Resonance (NMR) and AC Impedance Spectroscopy techniques, as a function of temperature. Below are a few noteworthy observations. Figure 1. VFT plots of the ionic conductivity for AlCl3:AA (left) and AlCl3:PA (right) DES electrolytes. Thirdly, the variable temperature 1H and 27Al spectra and T1 data for the pure and additives included DES electrolytes were very dependent on concentration, additive type and concentration, and species type. For example, in the 1:1 molar ratio electrolyte, the assigned AlCl2(amide)+ species had the longest T1, while the AlCl2(amide)2 + had the shortest. Additionally, the inclusion of additives such as fluoroethylene carbonate (FEC) and propylene carbonate (PC) caused species specific increasing local ion dynamics, possibly through the reduction of bulk viscosity effects and Coulombic interactions. These results and more will be expounded upon in our presentation.Firstly, for both AlCl3:PA and AlCl3:BA DES electrolytes, a maximum in ionic conductivity was observed at the 1.3:1 molar ratio. For AlCl3:AA DES the maximum occurred at the 1.5:1 molar ratio. Secondly, for the three amides conductivity values fell in the range of ~1 – 11 mS/cm over the temperature range of 288 – 363K. Additionally, the temperature dependence displayed curve-like behavior and were fitted using the VFT equation to reveal high levels of fragility and dynamic behaviors similarities to some pure ILs where the effective inter-conversion between the trans and cis conformations of the anion facilitated faster ion dynamics. Figure 1

Target-Specific Superparamagnetic Hydrogel with Excellent pH Sensitivity and Reversibility: A Promising Platform for Biomedical Applications.

Superparamagnetism has been widely used for many biomedical applications, such as early detection of inflammatory cancer and diabetes, magnetic resonance imaging (MRI), hyperthermia, etc., whereas incorporation of superparamagnetism in stimulus-responsive hydrogels has now gained substantial interest and attention for application in these fields. Recently, pH-responsive superparamagnetic hydrogels showing the potential use in disease diagnosis, biosensors, polymeric drug carriers, and implantable devices, have been developed based on the fact that pH is an important environmental factor in the body and some disease states manifest themselves by a change in the pH value. However, improvement in pH sensitivity of magnetic hydrogels is a dire need for their practical applications. In this study, we report the distinctly high pH sensitivity of new synthesized dual-responsive magnetic hydrogel nanocomposites, which was accomplished by copolymerization (free-radical polymerization) of two pH-sensitive monomers, acrylic acid (AA) and vinylsulfonic acid (VSA) with an optimum ratio, in the presence of presynthesized superparamagnetic iron oxide nanoparticles (Fe3O4(OH)x). The monomers contain pH-sensitive functional groups (COO– and SO3– for AA and VSA, respectively), and they have also been widely used as biomaterials because of the good biocompatibility. The pH sensitivity of the superparamagnetic hydrogel, poly(acrylic acid-co-vinylsulfonic acid), PAAVSA/Fe3O4, was investigated by swelling studies at different pH values from pH 7 to 1.4. Distinct pH reversibility of the system was also demonstrated through swelling/deswelling analysis. Thermal stability, chemical configuration, magnetic response, and structural properties of the system have been explored by suitable characterization techniques. Furthermore, the study reveals a pH-responsive significant change in the overall morphology and packing fraction of iron oxide nanoparticles in PAAVSA/Fe3O4 via energy-dispersive X-ray (EDX) elemental mapping with the field emission scanning electron microscopy (FESEM) study (for freeze-dried PAAVSA/Fe3O4, swelled at different pH values), implying a drastic change in susceptibility and induced saturation magnetization of the system. These important features could be easily utilized for the purpose of diagnosis using magnetic probe and/or impedance analysis techniques.

Order and Temperatures of Magnetic Transitions in a Ni₅₁.₉Mn₂₇.₀Ga₂₁.₁ Alloy

The existence of two Curie temperatures in the temperature interval of the martensitic phase of a Ni51.9Mn27.0Ga21.1 alloy has been verified. This phenomenon was confirmed in both magnetic and electrical impedance measurements. Additionally, modified Arrott plot calculations were employed to determine order and temperatures of magnetic transitions occurring in a Ni51.9Mn27.0Ga21.1 alloy. The results of the calculations are in line with the ones obtained in the experiments. They indicate that the second-order transitions on cooling and heating in this alloy occur at different temperatures with thermal hysteresis of ~7 K. The measurements of the dependence of AC impedance on temperature allowed to distinguish these magnetic transitions from the nearby martensitic one.