Magnetic Measurements Research Articles

Magnetic vortex γ-Fe2O3 nanospheres decorated with gold nanoparticles for dual hyperthermia treatment

In this work, multifunctional systems with potential applications for dual control of thermal heat delivery are developed. For this purpose, the nanosystems produced consist of vortex iron oxide nanospheres (VIONS) decorated with different amounts of gold nanoparticles (AuNPs). The VIONS were synthesized using the solvothermal reduction method, resulting in a 204 ± 24 nm diameter and meeting the requirements for biomedical applications. Magnetic measurements revealed that these systems are composed mainly of maghemite (γ-Fe2O3), exhibiting relatively low coercivity and moderate saturation magnetization, both of which serve as indicative attributes of an exceptional magnetic vortex state as validated by electron holography microscopy. The decoration with gold NPs was achieved through deposition-precipitation, involving the deposition of gold hydroxide on the surface of the previously amine-modified iron oxide NPs, followed by the concurrent reduction of Au3+. Furthermore, the gold NP size modulation was investigated by consecutively adding Au3+ to obtain gold NPs that interact with light differently depending on their size. The study provides crucial information that can aid the decoration of magnetic iron oxide nanospheres with AuNPs with tailored magnetic and optical properties; consequently, they may be promising candidates for magnetic and photothermal hyperthermia based on three-dimensional magnetic vortex structures.

Magnetic properties and linear negative magnetocapacitance in rutile like LiFe2SbO6

Abstract We report the high-temperature magnetic ordering and the observation of linear negative magnetocapacitance mediated by a low-temperature magnetic phase crossover in the compound LiFe2SbO6. The combined observations of the absence of a second harmonic generation (SHG) signal, and Rietveld refinements of X-ray and neutron powder diffraction (NPD) patterns of the sample confirm that LiFe2SbO6 crystalizes in a centrosymmetric Pnnm structure. The DC magnetization measurements reveal that an antiferromagnetic ordering sets in at high temperature (TN= 850). The magnetic anomaly in the DC magnetization at a lower temperature T = 13 K, is corroborated by AC susceptibility and the specific heat measurements. We observe a linear negative magnetocapacitance below T = 13 K, demonstrating an indirect magneto-dielectric coupling. Further, the neutron powder diffraction study reveals a collinear antiferromagnetic ordering with a wavevector k = (0, 0, 0).

Real-time equilibrium reconstruction by multi-task learning neural network based on HL-3 tokamak

Abstract A neural network model, EFITNN, has been developed capable of real-time magnetic equilibrium reconstruction based on HL-3 tokamak magnetic measurement signals. The model processes inputs from 68 channels of magnetic measurement data gathered from 1159 HL-3 experimental discharges, including plasmas current, loop voltage, and the poloidal magnetic fields measured by probes. The outputs of the model feature eight key plasmas parameters, alongside high-resolution ( 129 × 129 ) reconstructions of the toroidal current density J P and poloidal magnetic flux distributions Ψ rz . Moreover, the network’s architecture employs a multi-task learning structure, which enables the sharing of weights and mutual correction among different outputs, and leads to increase the model’s accuracy by up to 32%. The performance of EFITNN demonstrates remarkable consistency with the offline EFIT, achieving average R 2 = 0.941, 0.997 and 0.959 for eight plasmas parameters, Ψ rz and J P , respectively. The model’s robust generalization capabilities are particularly evident in its successful predictions of quasi-snowflake (QSF) divertor configurations and its adept handling of data from shot numbers or plasmas current intervals not previously encountered during training. Compared to numerical methods, EFITNN significantly enhances computational efficiency with average computation time ranging from 0.08 ms to 0.45 ms, indicating its potential utility in real-time isoflux control and plasmas profile management.

Imaging magnetic transition of magnetite to megabar pressures using quantum sensors in diamond anvil cell

High-pressure diamond anvil cells have been widely used to create novel states of matter. Nevertheless, the lack of universal in-situ magnetic measurement techniques at megabar pressures makes it difficult to understand the underlying physics of materials’ behavior at extreme conditions, such as high-temperature superconductivity of hydrides and the formation or destruction of the local magnetic moments in magnetic systems. Here, we break through the limitations of pressure on quantum sensors by modulating the uniaxial stress along the nitrogen-vacancy axis and develop the in-situ magnetic detection technique at megabar pressures with high sensitivity (~1μT/Hz\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\sim 1{{{\\rm{\\mu }}}}{{{\\rm{T}}}}/\\sqrt{{{{\\rm{Hz}}}}}$$\\end{document}) and sub-microscale spatial resolution. By directly imaging the magnetic field and the evolution of magnetic domains, we observe the macroscopic magnetic transition of Fe3O4 in the megabar pressure range from ferrimagnetic (α-Fe3O4) to weak ferromagnetic (β-Fe3O4) and finally to paramagnetic (γ-Fe3O4). The scenarios for magnetic changes in Fe3O4 characterized here shed light on the direct magnetic microstructure observation in bulk materials at high pressure and contribute to understanding magnetism evolution in the presence of numerous complex factors such as spin crossover, altered magnetic interactions and structural phase transitions.

Structural, optical, and magnetic properties study of Dy-Cr co-doped bismuth ferrite (BFO) nanoparticles

Dysprosium-Chromium co-doped bismuth ferrite (Bi0.9Dy0.1Fe1-xCrxO3, x = 0, 0.05, and 0.1) nanoparticles were prepared by the sol–gel technique. The formed gel, held in an evaporating dish, was burned in a hot oven at 210 °C to form fluffy ash. The ground-burnt ash was sintered in a temperature-programmed electric furnace for 5 h at 820°C. The XRD results confirmed that all the prepared samples were in a rhombohedra structure with space group R3c. The XRD analysis revealed that the crystallite size decreased from 19.75 nm to 17.97 nm as the co-dopants increased. The energy dispersive x-ray (EDX) spectroscopy confirmed the presence of the ions as per the stoichiometry ratio. The VSM magnetic measurements revealed that the magnetic parameters, saturation magnetization (Ms), and remnant magnetization (Mr) relatively increased from 1.34 emu/g to 1.63 emu/g, and 0.262 to 0.412, respectively, with increasing the co-dopants, but the coercive field decreased. The UV–Vis measurement showed that the energy band gap (Eg) increased from 1.93 eV to 2.15 eV as the concentration of the co-dopants increased from x = 0 to x = 0.10.

Effects of Injected Current Streams on MHD Equilibrium Reconstruction of Local Helicity Injection Plasmas in a Spherical Tokamak

Open field line currents are intrinsic to DC helicity injection plasma startup and pose a challenge for inferring the plasma equilibrium with standard reconstruction analysis. Local helicity injection (LHI) is a type of DC helicity injection which uses small, modular current sources to drive force-free current along helical field lines to produce tokamak plasmas. MHD modeling and magnetic measurements during LHI indicate the injected current streams remain coherent as helical structures on the outboard edge of a core toroidal plasma that is tokamak-like in a toroidally averaged sense. To extract core plasma equilibrium properties, external magnetic diagnostics corrected for contributions from the injected current streams are fitted by a standard Grad-Shafranov equilibrium code. An iterative approach for estimating and subtracting the stream contributions from the diagnostic signals is described and applied to a model equilibrium database to reduce systematic errors introduced by the streams. Convergence is usually attained with 2 to 4 iterations, with derived equilibrium parameters matching the prescribed axisymmetric core values to within estimated experimental uncertainties. Accurate recovery of core parameters occurs when the ratio of the net toroidal windup current from the streams to the core plasma current is less than 0.2, which is typically satisfied in most experiments.

Prediction of MRI relaxometry in the presence of hepatic steatosis by Monte Carlo simulations.

To develop Monte Carlo simulations to predict the relationship of with liver fat content at 1.5T and 3.0T. For various fat fractions (FFs) from 1% to 25%, four types of virtual liver models were developed by incorporating the size and spatial distribution of fat droplets. Magnetic fields were then generated under different fat susceptibilities at 1.5T and 3.0T, and proton movement was simulated for phase accrual and MRI signal synthesis. The synthesized signal was fit to single-peak and multi-peak fat signal models for and proton density fat fraction (PDFF) predictions. In addition, the relationships between and PDFF predictions were compared with in vivo calibrations and Bland-Altman analysis was performed to quantitatively evaluate the effects of these components (type of virtual liver model, fat susceptibility, and fat signal model) on predictions. A virtual liver model with realistic morphology of fat droplets was demonstrated, and and PDFF values were predicted by Monte Carlo simulations at 1.5T and 3.0T. predictions were linearly correlated with PDFF, while the slope was unaffected by the type of virtual liver model and increased as fat susceptibility increased. Compared with in vivo calibrations, the multi-peak fat signal model showed superior performance to the single-peak fat signal model, which yielded an underestimation of liver fat. The -PDFF relationships by simulations with fat susceptibility of 0.6ppm and the multi-peak fat signal model were ( , ) at 1.5T and ( , ) at 3.0T. Monte Carlo simulations provide a new means for -PDFF prediction, which is primarily determined by fat susceptibility, fat signal model, and magnetic field strength. Accurate -PDFF calibration has the potential to correct the effect of fat on quantification, and may be helpful for accurate measurements in liver iron overload. In this study, a Monte Carlo simulation of hepatic steatosis was developed to predict the relationship between and PDFF. Furthermore, the effects of fat droplet morphology, fat susceptibility, fat signal model, and magnetic field strength were evaluated for the -PDFF calibration. Our results suggest that Monte Carlo simulations provide a new means for -PDFF prediction and this means can be easily generated for various regimes, such as simulations with higher fields and different echo times, as well as correction of magnetic susceptibility measurements for liver iron quantification.

Effect of magnetic entropy in the thermoelectric properties of Fe-doped Fe2VAl full-Heusler alloy

The effect of spin entropy on the transport of heat/charge carriers in the Fe-doped full-Heusler alloy Fe2+xVAl1-x with x = 0–0.1 has been studied through low-temperature magnetic and thermoelectric measurements. Magnetization (M) measurements confirm itinerant-electron weak-ferromagnetic behavior. A systematic increase of the magnetic transition temperature TC (from 40 K to 223 K) and of the saturation magnetization (from 0.13 to 0.41μB/Fe) with increasing Fe doping (from x = 0 to 0.1) is observed. Applying a magnetic field causes significant suppression of the Seebeck coefficient (S) and the entropy term (S/T) with a negative magnetoresistance near TC for all weak-ferromagnetic samples, demonstrating a clear effect of spin fluctuations. Analyzing M(T) and S(T), we rule out sizeable magnon drag contributions. A large spin fluctuations-induced enhancement in the thermoelectric power factor PF of about 18 % is achieved for x = 0.1 near TC when compared to measurements in a magnetic field of 7 T. The actual improvement in PF is even much higher, as the S shows a significant enhancement (about 34 %) compared to the estimated diffusion term of S(T) at TC. The number of point defects also increases with Fe doping, causing a significant reduction of the lattice thermal conductivity. This study demonstrates the role of spin fluctuations in enhancing the thermopower/thermoelectric performance of Fe-doped Fe2VAl and opens a vista for the strategy's applicability for various thermoelectric materials.

Preparation and Ground-State Electronic Structure of Heterobimetallic Yb-PtIV-Alkyl Complexes.

This article focuses on the synthesis of heterobimetallic complexes of lanthanide and platinum. It describes the synthesis of the Cp*Yb(bipym)PtMe2 complex and its characterization, followed by its reactivity with oxidants, giving access to various Pt + IV compounds of trismethyl (PtMe3) and tetramethyl (PtMe4) fragments. Characterization of the electronic properties of the complexes by magnetic measurements demonstrated that the tetramethyl complex possesses a singlet ground state. The trismethyl fragments, on the other hand, have a ground state that evolves as a function of the ligand saturating the coordination sphere: a singlet for triflate and pyridine and a triplet for iodine, demonstrating the capacity for simple tuning of the electronic structure of these complexes. While the addition of B(C6F5)3 to the platinum + II bis methyl complex leads to FLP-like reactivity triggering THF opening, reactivity with [Ph3C]+[BPh4]- leads to oxidation of the bipym ligand. Furthermore, the light reactivity of the tetramethyl complex indicated the possible transfer of a methyl group, leading to functionalization of the bridging bipym ligand.

Towards non-invasive imaging through spinal-cord generated magnetic fields.

Non-invasive imaging of the human spinal cord is a vital tool for understanding the mechanisms underlying its functions in both healthy and pathological conditions. However, non-invasive imaging presents a significant methodological challenge because the spinal cord is difficult to access with conventional neurophysiological approaches, due to its proximity to other organs and muscles, as well as the physiological movements caused by respiration, heartbeats, and cerebrospinal fluid (CSF) flow. Here, we discuss the present state and future directions of spinal cord imaging, with a focus on the estimation of current flow through magnetic field measurements. We discuss existing cryogenic (superconducting) and non-cryogenic (optically-pumped magnetometer-based, OPM) systems, and highlight their strengths and limitations for studying human spinal cord function. While significant challenges remain, particularly in source imaging and interference rejection, magnetic field-based neuroimaging offers a novel avenue for advancing research in various areas. These include sensorimotor processing, cortico-spinal interplay, brain and spinal cord plasticity during learning and recovery from injury, and pain perception. Additionally, this technology holds promise for diagnosing and optimizing the treatment of spinal cord disorders.

A bis-Phenolate Carbene-Supported bis-μ-Oxo Iron(IV/IV) Complex with a [FeIV(μ-O)2FeIV] Diamond Core Derived from Dioxygen Activation.

The diiron(II) complex, [(OCO)Fe(MeCN)]2 (1, MeCN = acetonitrile), supported by the bis-phenolate carbene pincer ligand, 1,3-bis(3,5-di-tert-butyl-2-hydroxyphenyl)benzimidazolin-2-ylidene (OCO), was synthesized and characterized by single-crystal X-ray diffraction, 1H nuclear magnetic resonance, infrared (IR) vibrational, ultraviolet/visible/near-infrared (UV/vis/NIR) electronic absorption, 57Fe Mössbauer, X-band electron paramagnetic resonance (EPR) and SQUID magnetization measurements. Complex 1 activates dioxygen to yield the diferric, μ-oxo-bridged complex [(OCO)Fe(py)(μ-O)Fe(O(C═O)O)(py)] (2) that was isolated and fully characterized. In 2, one of the iron-carbene bonds was oxidized to give a urea motif, resulting in an O(CNHC═O)O binding site, while the other Fe(OCO) unit remained unchanged. When the reaction is performed at -80 °C, an intensively colored, purple intermediate is observed (INT, λmax = 570 nm; ε = 5600 mol L-1 cm-1). INT acts as a sluggish oxidant, reacting only with easily oxidizable substrates, such as PPh3 or 2-phenylpropionic aldehyde (2-PPA). The identity of INT can be best described as a dinuclear complex containing a closed diamond core motif [(OCO)FeIV(μ-O)2FeIV(OCO)]. This proposal is based on extensive spectroscopic [UV/vis/NIR electronic absorption, 57Fe Mössbauer, X-band EPR, resonance Raman (rRaman), X-ray absorption, and nuclear resonance vibrational (NRVS)] and computational studies. The conversion of the diiron(II) complex 1 to the oxo diiron(IV) intermediate INT is reminiscent of the O2 activation process in soluble methane monooxygenases (sMMO). Most importantly, the low reactivity of INT supports the consensus that the [FeIV(μ-O)2FeIV] diamond core in sMMO is kinetically inert and needs to open up to terminal FeIV═O cores to react with the strong C-H bonds of methane.

Hofmann Clathrates: A "Blue Box" Approach to Modulate Spin-Crossover Properties.

Hofmann coordination polymers (CPs) with cationic ligands provide an innovative strategy for recognizing π-electron-rich aromatic molecules - similar to the "little blue box". In this study, we demonstrate that hydroquinone molecules can be incorporated into these coordination polymers when redox-active bipyridinium derivatives are used as axial ligands. The insertion leads to a significant structural modification, resulting in a shift of the spin transition by 150 K and an approximate 23 % increase in volume, caused by the strong donor-acceptor π-π stacking interaction formed between the ligands and the guest molecule. These findings have been confirmed through temperature-dependent single crystal X-ray diffraction, magnetic measurements and optical reflectivity measurements.

Hofmann Clathrates: A “Blue Box” Approach to Modulate Spin‐Crossover Properties

AbstractHofmann coordination polymers (CPs) with cationic ligands provide an innovative strategy for recognizing π‐electron‐rich aromatic molecules – similar to the “little blue box”. In this study, we demonstrate that hydroquinone molecules can be incorporated into these coordination polymers when redox‐active bipyridinium derivatives are used as axial ligands. The insertion leads to a significant structural modification, resulting in a shift of the spin transition by 150 K and an approximate 23 % increase in volume, caused by the strong donor‐acceptor π‐π stacking interaction formed between the ligands and the guest molecule. These findings have been confirmed through temperature‐dependent single crystal X‐ray diffraction, magnetic measurements and optical reflectivity measurements.

Analysis of interference fringes in a long-wave infrared full Stokes polarimeter based on rotating waveplates

In the long-wave infrared (LWIR, 8–15 µm) band, the interference effect of polarization elements becomes an issue in polarimetry due to defects in the anti-reflective coatings. The paper describes an analysis and optimization method for the rotating-waveplates-based Stokes polarimeter, to eliminate interference fringes and improve polarization measurement accuracy in LWIR. An interference model was established based on the theory of polarized light and thin-film optics. Different modulation schemes were simulated and analyzed to obtain an optimized Stokes polarimeter, reducing the instrumental polarization to less than 1E-3. Furthermore, experimental validation was conducted by the Accurate Infrared Magnetic Field Measurements of the Sun (AIMS) telescope. The result shows that the instrumental polarization was less than 2E-3, consistent with the simulation.

Retinol-binding protein 4 is a potential biomarker of changes in lean mass in postmenopausal women.

Identifying biomarkers can help in the early detection of muscle loss and drive the development of new therapies. Research suggests a potential link between retinol-binding protein 4 (RBP4) and muscle mass, particularly in postmenopausal women. This study aimed to examine the association between baseline RBP4 levels and changes in appendicular lean mass (ALM), an indicator of muscle mass, in postmenopausal women. A 12-month follow-up period (n=153) included baseline and 12-month ALM assessments using DXA. ALM was normalized to squared height (ALMI). Baseline evaluations encompassed insulin resistance via HOMA-IR and immunoassay magnetic bead panel measurements of RPB4, IL-6, TNF-α, and IL-10. Postmenopausal women were categorized into higher (n=77) and lower (n=76) RPB4 groups based on baseline RPB4 values. Their changes in ALMI were compared using Mann-Whitney tests. General linear model was employed to evaluate the predictive power of baseline RBP4 for ALMI changes, adjusting for confounding variables: age, physical activity, smoking status, body fat, HOMA-IR, inflammatory markers (TNF-α and IL-6), and anti-inflammatory factor (IL-10). The higher RBP4 group exhibited a more pronounced reduction in ALMI compared to the lower RBP4 group (Higher RBP4 = -0.39kg/m2, 95% CI: -0.48 to -0.31kg/m2vs. Lower RBP4 = -0.24kg/m2, 95% CI: -0.32 to -0.15kg/m2, P=0.011). After adjusting for confounding factors, the association between baseline RBP4 changes and ALMI remained (b = -0.008, SE=0.002, P<0.001), indicating higher baseline RBP4 values linked to greater ALMI reduction. Our findings support RBP4 as a potential biomarker for changes in muscle mass in postmenopausal women.

Fermi surface and Lifshitz transitions of a ferromagnetic superconductor under external magnetic fields

Lifshitz transitions are being increasingly recognized as significant in a wide variety of strongly correlated and topological materials, and understanding the origin and influence of Lifshitz transitions is leading to deeper understanding of key aspects of magnetic, transport, or quantum critical behavior. In the ferromagnetic superconductor UCoGe, a magnetic field applied along the c axis has been shown to induce a series of anomalies in both transport and thermopower that may be caused by Lifshitz transitions. The need to understand the subtleties of the relationship between magnetism, superconductivity and a heavy-electron Fermi surface in the ferromagnetic superconductors makes it important to explore if and why a series of magnetic-field-induced Lifshitz transitions occurs in UCoGe. Here we report magnetic susceptibility measurements of UCoGe, performed at temperatures down to 45 mK and magnetic fields (μ0H||c) up to 30 T. We observe a series of clearly defined features in the susceptibility, and multiple sets of strongly field-dependent de Haas-van Alphen oscillations, from which we extract detailed field dependence of the quasiparticle properties. We complement our experimental results with density functional theory band structure calculations, and include a simple model of the influence of magnetic field on the calculated Fermi surface. By comparing experimental and calculated results, we determine the likely shape of the Fermi surface and identify candidate Lifshitz transitions that could correspond to two of the features in susceptibility. We connect these results to the development of magnetization in the system. Published by the American Physical Society 2024

Anion and Cation Dynamics in Mixed-Anion Hydroborate Na3(BH4)(B12H12): 1H, 11B, and 23Na NMR Studies

Sodium borohydride-closo-hydroborate Na3(BH4)(B12H12) exhibits high room-temperature ionic conductivity and high electrochemical stability. To study the dynamical properties of this mixed-anion compound at the microscopic level, we have measured the 1H, 11B, and 23Na nuclear magnetic resonance spectra and nuclear spin-lattice relaxation rates over the temperature range of 8–573 K. Our 1H and 11B spin-lattice relaxation measurements have revealed two types of reorientational jump motion. The faster motional process attributed to reorientations of the [BH4]− anions is characterized by an activation energy of 159 meV, and the corresponding reorientational jump rate reaches ~108 s−1 near 130 K. The slower process ascribed to reorientations of the larger [B12H12]− anions is characterized by an activation energy of 319 meV, and the corresponding reorientational jump rate reaches ~108 s−1 near 240 K. The results of the 23Na nuclear magnetic resonance measurements are consistent with the fast long-range diffusion of Na+ ions in Na3(BH4)(B12H12). The diffusive jump rate of Na+ is found to reach ~104 s−1 at 300 K and ~8 × 108 s−1 at 530 K. A comparison of these jump rates with the ionic conductivity data suggests the importance of correlations between diffusing ions.

Ta4SBr11: A Cluster Mott Insulator with a Corrugated, Van der Waals Layered Structure.

The compound Ta4SBr11 was prepared by a comproportionation reaction of tantalum bromide with tantalum and elemental sulfur. The crystal structure, as refined by single-crystal X-ray diffraction, is composed of clusters with Ta4S cores, arranged in corrugated van der Waals layers. Individual layers appear to be displaced relative to each other along one direction. Successful crystal growth in a melt of CsBr yielded black platelets of Ta4SBr11, which were used to investigate the electrical properties of the compound. The electronic structure was studied by diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy and by density functional theory (DFT) band structure calculations, revealing this material to be a small-gap semiconductor. DFT results, in combination with magnetic susceptibility measurements, suggest that metallicity originating from the one unpaired Ta d electron per cluster is most likely suppressed by electronic correlations, forming a cluster Mott insulator.

Synthesis, structural study, antimicrobial activity and theoretical treatment of Cr(III), Ni(II), Pt(IV) and Zn(II) complexes with 2-hydroxy-4-Nitro phenyl piperonalidene

The complexes of the 2-hydroxy-4-Nitro phenyl piperonalidene with metal ions Cr(III), Ni(II), Pt(IV) and Zn(II) were prepared in ethanolic solution. These complexes were characterized by spectroscopic methods, conductivity, metal analyses and magnetic moment measurements. The nature of the complexes formed in ethanolic solution was study following the molar ratio method. From the spectral studies, monomer structures proposed for the nickel (II) and Zinc (II) complexes while dimeric structures for the chromium (III) and platinum (IV) were proposed. Octahedral geometry was suggested for all prepared complexes except zinc (II) has tetrahedral geometry, Structural geometries of these compounds were also suggested in gas phase by using hyper chem-8 program for the molecular mechanics and semi-empirical calculations. The heat of formation and binding energy for the prepared compounds was calculated by using PM3 and AMBER methods. The method of PM3 was used for evaluate the vibration spectra for the imine and starting material as authentic compound. Preliminary in vitro tests for antibacterial and antifungal activity show that most of the prepared compounds display good activity to (Staphylococcus aureus), (Escherichia coli) and (Candida albicans).

Effect of charge-discharge with higher capacitance performance of Ni-substituted CoFe2O4 magnetic nanoparticles for energy storage

In this work, we synthesized NixCo1-xFe2O4 (0 ≤ x ≤ 0.8) magnetic nanoparticles (MNPs) by using ultrasonication-assisted reverse chemical co-precipitation method. The X-ray diffraction (XRD) patterns confirm the single-phase with mixed spinel structure of the NixCo1-xFe2O4 (0 ≤ x ≤ 0.8) MNPs with the crystallite size range between 12 nm - 17 nm. The molecular dynamics and oleic acid coated Ni-substituted CoFe2O4 magnetic nanoparticles were confirmed by FTIR measurements. The surface composition of NixCo1-xFe2O4 (0 ≤ x ≤ 0.8) MNPs (Ni, Co, Fe and O) and their oxidation states were estimated using X-ray photoelectron spectroscopy. The NixCo1-xFe2O4 (0 ≤ x ≤ 0.8) MNPs are spherical in shape and polycrystalline in nature, confirmed by FESEM and HRTEM measurements. The Ni-substituted CoFe2O4 MNPs with higher zeta potential (ζ) from −24 mV to -41 mV with an increase in Ni concentration, signifies the stable colloidal stability due to the electrostatic repulsion between MNPs. The DC magnetization (M-vs-H) measurements reveal the ferrimagnetic behavior of NixCo1-xFe2O4 (0 ≤ x ≤ 0.8) MNPs, which suppress the saturation magnetization (MS) from 48.6 emu/g to 5.3 emu/g with the enhanced coercivity (HC) from 335 Oe to 1700 Oe with the substitution of Ni2+ ions is in corroboration with electron paramagnetic resonance (EPR) measurements. The enhanced EPR resonance field (Hres = 2335 Oe - 3261 Oe) with the substitution of Ni2+ ions is attributed to the generation of oxygen vacancies and defects, which are predominant in Ni0.8Co0.2Fe2O4, resulting in significantly enhanced electrochemical performance. Therefore, the three-electrode system was utilized to investigate the electrochemical properties of NixCo1-xFe2O4 (0 ≤ x ≤ 0.8) MNPs. The Ni-substituted CoFe2O4 MNPs have demonstrated significantly enhanced capacity retention of 77 % even after 5000 cycles in 1 M H2SO4 electrolyte solution. NixCo1-xFe2O4 (0 ≤ x ≤ 0.8) MNPs exhibit an excellent specific capacity (Cs) of 794.5 F/g at a current density of 1 A/g, signifies the rate of redox reaction at surface electrolyte interface (SEI) is greatly influenced by the surface to volume ratio. Thus, with the enhancement of Ni2+ ions, redox reaction kinetics might become more efficient resulting in the enhanced charge storage capacity.