Magnetic Behavior Research Articles

Reconstructing Magnetic Hysteresis Behavior with Flux Model and Identifying Parameters for Dual-Coil MR Actuator

Reconstructing Magnetic Hysteresis Behavior with Flux Model and Identifying Parameters for Dual-Coil MR Actuator

Magnetic elastomer composites with tunable magnetization behaviors for flexible magnetic transducers

AbstractMagnetic elastomer composites are extending the field of soft robotics by integrating the flexibility of elastomers with the versatile performance of magnetic materials. In this work, a series of magnetic elastomers (BaCoxTixFe12–2xO19/PDMS) with tunable magnetic response have been successfully synthesized. In this composite, the magnetic component consists of Co‐Ti co‐doped barium hexaferrite (BaCoxTixFe12–2xO19, BCTF) nano powders, and the matrix is made of polydimethylsiloxane (PDMS). The coercivity (Hc) of BCTF can be reduced from 3950 Oe to 70 Oe, which bestow on the magnetic elastomer different magnetic response behavior. These magnetic elastomer composites obtained by blending have low Young's modulus, approximately 1.5 MPa. Furthermore, when applying the same external magnetic field, BaCo1.2Ti1.2Fe9.6O19/PDMS the magnetic deformation Angle can be as high as 60°. These magnetic elastomers exhibit different magnetic‐induced deformation owing to the adjustable permeability of the magnetic nanoparticles. This research significantly advances the design of applications with specific magnetic characteristics, such as sensors and transducers, thus opening new horizons for innovation in soft robotics and related fields.Highlights All elastomer composite exhibit a low modulus of approximately 1.5 MPa. These composites exhibit different magnetic response behaviors. This research provides a solution for the innovation of transducers.

Analytical study of magnetic properties of quantum dot/ring system: Rashba, magnetic field, and electron-electron effects

Abstract Magnetic behavior of a two-electron quantum dot/ring system are analytically studied with electron-electron (e-e) interaction taking into account the Rashba spin-orbit interaction (SOI) and magnetic field. The Jacobi transformation has been employed to separate the Hamiltonian of the system to the center of mass and relative terms. The Schrödinger equation is analytically solved, and energy spectra are obtained. Then, the magnetization and susceptibility are calculated. The magnetization decreases by rising the magnetic field without and with SOI and also without e-e interaction. Also, SOI slightly modifies the magnetization of the system without e-e interaction. The susceptibility displays a peak structure as the magnetic field changes from low values to high values. The susceptibility by considering e-e interaction and without SOI is always negative and its value decreases by rising the magnetic field. The susceptibility displays a transition from diamagnetic to paramagnetic with e-e interaction and SOI.

Influence of Pressure on Electronic, Magnetic Behavior, and Fermi Surface Studies of SrFe2X2 (X = P, As, Sb) Iron-Based Superconductors

Influence of Pressure on Electronic, Magnetic Behavior, and Fermi Surface Studies of SrFe2X2 (X = P, As, Sb) Iron-Based Superconductors

The effect of diameter on hysteresis loop squareness in iron nanowires array by micromagnetic simulation

Utilization of micromagnetic simulation is a very attractive subject to understand the magnetic behavior of nanowire arrays that tune their geometrical features and magnetic properties. Here, the micromagnetic simulations utilize to investigation of the single, and a 3 × 3 array of iron nanowires with diameters from 30 to 60 nm. The diameter size and the distance between the wires are selected according to the fabrication of iron nanowires grown in alumina templates. The simulation indicated that an increase in diameter led to a decrease in the coercive field and squareness ratio in both single nanowires and nanowire arrays. Besides, the simulation discloses that the magnetization reversal process of the nanowires with diameters more than 42 nm occurs through the nucleation and propagation of vortex domain walls. In the nanowires array, an increase in wire diameter increases the number of jumps in the hysteresis loop, indicating a more magnetic interaction between the nanowires.

Spin filtering and quantum transport with transition metal-doped hydrogenated silicon quantum dot

Spin filtering is a fundamental operation in spintronics, enabling the generation and detection of spin-polarized carriers. Here, we proposed and theoretically demonstrated that a 3d transition metal (TM) doped hydrogenated silicon quantum dot (TM:H-SiQD) is a suitable candidate for spin-filter devices. Using density functional theory, we investigate the structure, electronic properties, and magnetic behavior of TM:H-SiQD. Our calculations demonstrate that Mn:H-SiQD exhibits the highest stability. The designed spin-filter device using Mn:H-SiQD shows a spin-filtering efficiency of 99.9% at 300 K electrode temperature along with very high conductance. This remarkable efficiency positions it as a promising candidate for spintronic devices.

Osmium(III) Acetylacetonate and Its Missing Polymorph: A Magnetic and Structural Investigation.

Despite the potential for their application, the magnetic behavior of complexes containing 4d and 5d metal ions is underexplored, evidencing the need for benchmark multi-technique studies on simple molecules. We report here a structural and magnetic study on osmium(III) acetylacetonate [Os(acac)3]. X-ray single crystal diffraction did not allow us to determine the structure of the β-polymorph of [Os(acac)3]. The combined magnetic (dc magnetic measurements on powder and cantilever torque magnetometry on single crystal) and spectroscopic (electron paramagnetic resonance, EPR) characterization is here used to provide further evidence that its structure is indeed the one of the orthorhombic "missing polymorph", analogous to the ruthenium(III) derivative. Our study shows that all acetylacetonate complexes of the eighth group of the periodic table show dimorphism and are isomorphic. The EPR characterization allowed the experimental assessment of the easy axis nature of the ground doublet and the determination of the first hyperfine coupling in an osmium complex. Torque magnetometry, applied here for the first time on an osmium-based molecule, determined the orientation of the easy axis along the pseudo C3 axis of the complex. Ac magnetometric measurements revealed in-field slow relaxation of the magnetization further slowed by the suppression of dipolar fields via magnetic dilution in the isostructural gallium(III) analogue.

Exploring the magnetic behavior of potassium-doped Cu0.5Tl0.5Ba2Ca2Cu3-xKxO10-δ (x=0, 1, 2.5, 3) superconductors

This study investigates the superconducting and magnetic behaviour of Potassium-doped Cu0.5Tl0.5Ba2Ca2Cu3-xKxO10-δ superconductors by varying potassium-concentrations (x = 0, 1, 2.5, 3). We have synthesized the samples by two-step solid-state-reaction method and explored their superconducting features by XRD analysis, SEM and resistivity measurements. Through a comprehensive exploration of magnetic measurements i.e magnetization versus magnetic field and temperature, we aim to elucidate the impact of potassium doping on the diamagnetic characteristics of these superconductors. The results reveal that by raising the doping concentration of potassium, the orthorhombic unit cell's axis lengths decresese. The onset of superconductivity and the magnitude of diamagnetism are also decreased. The magnetic behavior of these samples was studied by field cooled and zero field cooled from 2 to 300 K and taking the hysteresis loops at temperatures 2 to 60 K. In the doped samples, the suppression of current density is steeper with increase in temperature. Doped atoms boost the population of localized defects, which serve as pinning centers. This study will contribute valuable information to the understanding of the relationship between magnetic behavior and the superconducting nature of complex oxide materials.

Coexistence of multiple magnetic interactions in oxygen-deficient V2O5 nanoparticles

This paper reports on the spin glass-like coexistence of competing magnetic orders in oxygen-deficient V2O5 nanoparticles with a broad size distribution. X-ray photoelectron spectroscopy yields the surface chemical stoichiometry of nearly V2O4.65 due to significant defect density. Temperature-dependent electrical conductivity and thermopower measurements demonstrate a polaronic conduction mechanism with a hopping energy of about 0.112 eV. The V2O5-δ sample exhibits strong field as well as temperature-dependent magnetic behaviour when measured with a SQUID magnetometer, showing positive magnetic susceptibility across the temperature range of 2-350 K. Field-cooled and zero-field-cooled data indicate hysteresis, suggesting glassy behaviour. The formation of small polarons due to oxygen vacancy defects, compensated by V4+ charge defects, results in Magneto-Electronic Phase Separation (MEPS) and various magnetic exchanges, as predicted by first-principle calculations. This is evidenced by the strong hybridisation of V orbitals in the vicinity of vacant oxygen site. An increase in V4+ defects shows an antiferromagnetic (AFM) component. The magnetic diversity in undoped V2O4.9 originates from defect density and their random distribution, leading to MEPS. This involves localised spins in polarons and ferromagnetic (FM) clusters on a paramagnetic (PM) background, while V4+ dimers induce AFM interactions. Electron paramagnetic resonance spectra measured at different temperatures indicate a dominant paramagnetic signal at a g-value of 1.97 due to oxygen defects, with a broad FM resonance-like hump. Both signals diminish with increasing temperature. Neutron diffraction data rules out long-range magnetic ordering, reflecting the composition as V2O4.886. Despite the FM hysteresis, no long-range order is observed in neutron diffraction data, consistent with the polaron cluster-like FM with MEPS nature. This detailed study shall advance the understanding of the diverse magnetic behaviour observed in undoped non-magnetic systems.

Magnetic phase transition and critical behavior of the chiral magnet [formula omitted]-Mn type Co7Zn7Mn6

We report a systematic study of magnetic transformation and magnetic critical behavior in the chiral magnet β-Mn type Co7Zn7Mn6. It undergoes a paramagnetic-ferromagnetic phase transition around 190 K and shows a spin glass state at 18 K. The critical exponents β= 0.685, γ= 1.385, and δ= 3.03 are obtained by the investigation of magnetic field dependence on magnetic-entropy change and the calculation with Widom scaling relation. The reliability of critical exponents is confirmed by the scaling equation. The strong reversed site disorder of β-Mn type Co7Zn7Mn6 results in the localized characterization of carriers and a slow development of ferromagnetic ordering state.

Self-Assembled Lanthanide Phosphinate Square Grids (Ln = Er, Dy, and Tb): Dy4 Shows SMM/SMT and Tb4 SMT Behavior.

Tetranuclear [2 × 2] square-grid-like LnIII clusters have been synthesized by reacting LnCl3·6H2O salts with bis[α-hydroxy(p-bromophenyl)methyl]phosphinic acid [R2PO2H, where R = CH(OH)PhBr] and pivalic acid. Single-crystal X-ray diffraction studies show the formation of [Me4N]2[Ln4(μ2-η1:η1-PO2R2)8(η2-CO2But)4(μ4-CO3)] [Ln = Er (1), Dy (2), and Tb (3)]. Direct-current studies reveal significant ferromagnetic interactions between DyIII in 2 and TbIII in 3 and an antiferromagnetic interaction between ErIII in 1. Dynamic magnetic susceptibility measurements confirm a single-molecule magnet (SMM) behavior in both 0 and 1200 Oe applied magnetic fields for 2. Complexes 2 and 3 show single molecular toroic (SMT) behavior with a mixed magnetic moment.

Magnetic exchange coupled composite behavior in the doped manganite nanoparticles: A proposed phenomenological model

In this paper, we comprehensively investigate the isothermal magnetization behavior of doped perovskite manganite nanoparticles. The focus is on understanding the impact of variation of particle sizes on the soft and hard magnetic phases with respect to the changes in the coercive field and remanent magnetization, both theoretically and experimentally. The study seeks to correlate experimental findings with the proposed phenomenological model to gain deeper insights into the underlying mechanisms governing exchange coupling and anisotropy effects in the nanocrystalline composites. The proposed phenomenological model beautifully demonstrates how the values of saturation magnetization and coercive field changes with changing the particle size in the nanocrystalline La0.48Ca0.52MnO3 (LCMO48) and La0.46Ca0.54MnO3 (LCMO46) compounds. In addition, the model provide an insights into the limitations of critical radius, size and shape of the nanocrystalline particle. This investigation looks into how the size of particles affects their magnetic properties, specifically coercive field and remanent magnetization.

Impact of orbital hybridization on spin-polarized electronic transport through Ni-MAPbI3 interfaces

The solution-processed methylammonium lead tri-iodine (MAPbI3), with long spin lifetimes and large spin diffusion lengths, has merit for developing stable perovskite spin valves (PeSV) with low saturation fields. By far, it remains challenging to avoid ill-defined ferromagnet-MAPbI3 interfaces during device fabrications using solution methods and to quantify the hybridized interfacial electronic and magnetic structures. Herein, an annealing-free method was developed for the fabrication of MAPbI3 based PeSV. In comparison to a thermally annealed device, an improved room temperature magnetoresistance (MR) was achieved. We found remarkable interfacial contributions to anisotropic magnetoresistance and MR. The first-principles calculation was further adopted to quantify the interfacial spin and orbital moments. Our results suggest that the orbital hybridization and the spin transfer are remarkable for the formation of the spin-dependent interfacial density of states. It consequently affects magnetic switching behaviors. This study holds an exceptionally important role for a deep understanding of the spin-polarized electronic transport through the Ni-MAPbI3 hybridized interface.

Chiral Homodinuclear Dysprosium Macrocyclic Complexes with Single‐molecule Magnetic Behaviours

A pair of enantiomerically chiral dysprosium homodinuclear complexes: [(acac)4Dy2(R,R,R,R‐L)] (R‐Dy) and [(acac)4Dy2(S,S,S,S‐L)] (S‐Dy) (Hacac = acetylacetone) have been synthesized based on macrocyclic chiral ligands (R,R,R,R‐H2L/S,S,S,S‐H2L), derived from the [2+2] template condensation of 4‐tert‐butyl‐2,6‐diformylphenol, dysprosium acetylacetonate and (1R,2R)‐/(1S,2S)‐1,2‐cyclohexanediamine, respectively. Circular dichroism spectra confirms their enantiomeric chirality. Single‐crystal structures show two crystallographic independent dysprosium(III) ions have square antiprismatic coordination with different D4d local symmetry. Furthermore, the selected R‐Dy complex owns the slow magnetic relaxation behaviour with the ferromagnetic Dy3+···Dy3+ coupling.

Enhanced soft magnetic properties with high frequency stability of pure iron powder cores via high-pressure compaction – An environment and cost saving solution as a prospective alternative to soft magnetic composites

The paper presents the analysis of the magnetic behaviour of soft magnetic powder compacts vs. the increasing compacting pressure. An unexpectedly positive result was obtained at a pressure of 1500 MPa, as the pure iron compact without coating of powder particles and without subsequent heat treatment showed very good magnetic properties compared to the class of soft magnetic composites (SMCs). In particular, the effective relative permeability of μeff ∼120, stable up to a frequency f ∼200 kHz, the maximum total relative permeability of μtotmax ∼700, and the specific electrical resistivity of ρR ∼10−5 Ω m. This phenomenon was explained on the basis of analyses of the samples microstructure, the magnetic and electrical properties, magnetization processes, inner demagnetizing fields, Barkhausen noise and thermal diffusivity. It was found that the grain size refinement inside iron particles occurs at certain elevated compaction pressure because the deformation bands gradually rise and break up with compaction pressure, leading to a higher resistivity of the compact thus to its SMC-like behaviour, despite the counteracting effect of increasing number of iron-iron bridges among neighbouring particles. The grain size refinement causes also the refinement of magnetic domain structure, which facilitates the magnetization reversal, although, the increased internal stresses and microstructural defects affect domain wall mobility negatively. The most favourable combination of the mentioned factors influences, finally resulting in the soft magnetic properties enhancement, appeared at 1500 MPa. Due to high-pressure compaction, the high density (above ∼95 % of iron density) of a compact was achieved, ensuring sufficient mechanical properties. The presented material can serve as a potential supplanter of SMCs in many applications as it provides evident advantages, such as its easy production with minimum chemical waste (because any additional chemical processes and substances needed for particle coatings in conventional SMCs are completely omitted), as well as easy recycling process, which makes it eco-friendly and cost-effective, nevertheless, maintaining the advantages of SMCs.

Synthesis, crystal structure, magnetic behaviour and thermal stability of a paddle-wheel copper(II) complex bearing equatorial 3,4-diethoxybenzoate ligands.

The binuclear paddle-wheel copper(II) complex tetrakis(μ-3,4-diethoxybenzoato-κ2O:O')bis[(ethanol-κO)copper(II)], [Cu2(C11H13O4)4(C2H6O)2], has been synthesized and characterized. In each molecule, two CuII centres are bridged in a syn-syn fashion by four equatorial 3,4-diethoxybenzoate ligands, the two axial positions being occupied by ethanol molecules. The thermal stability has been studied by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) techniques. The magnetic behaviour, studied by SQUID magnetometry, shows a CuII-CuII antiferromagnetic exchange interaction with 2J= -288 cm-1, a value that fits with a magnetic structure correlation established for compounds of this kind.

Sensitivity of Mild Hydrothermal Synthesis to the Reaction Conditions: Targeting Mixed-Metal Hexagonal Tungsten Bronze Fluorides AxM2+xM3+(1-x)F3 to Investigate Their Magnetic Behavior.

The synthesis of five quaternary hexagonal tungsten bronze (HTB) fluorides, AxM2+xM3+(1-x)F3, (A = Cs and Rb; M2+ = Co2+, Ni2+, and Zn2+; and M3+ = V3+) via a mild hydrothermal route is reported. The crystal structures and compositions were determined using a combination of single-crystal X-ray diffraction, Rietveld refinement of powder X-ray diffraction data, and inductively coupled plasma optical emission spectroscopy analysis. This study highlights the sensitivity of the mild hydrothermal method on the reaction temperature, solvent system, and quantity of starting reagents that directly influence the selective synthesis of kinetically stabilized fluoride materials, including hydrated fluorides, β-pyrochlores, and HTB. The magnetic susceptibility and isothermal magnetization data for all five compounds were collected, which revealed the existence of a strong antiferromagnetic component in these phases. The presence of the Kagome layer in the structure results in geometrical frustration and leads to frustration indexes ranging from 7 to 13 for these compounds.

Magnetic properties, critical behavior, and magnetocaloric effect of Nd1−xSrxMnO3 (0.2 ≤ x ≤ 0.5): The role of Sr doping concentration

Magnetic characteristics, magnetocaloric effect, and critical behavior of Nd1−xSrxMnO3 compounds by Sr doping (x = 0.2, 0.3, 0.4, 0.5) were studied. All samples maintained orthorhombic structures, but the space group changed from Pnma (No. 62) for x = 0.2, 0.3 to Imma (No. 74) for x = 0.4, 0.5. As Sr doping increased, the Curie temperature (TC), Curie–Weiss temperature (TCW), and magnetization increased, attributed to the double exchange (DE) interaction. A discrepancy between TCW and TC was observed due to the competition between polarons and DE interaction. The critical behavior was investigated systematically using the self-consistent (modified Arrott plots, MAP) method and the Kouvel–Fisher (KF) relation. The KF relation was suitable for the samples with x = 0.2 and 0.5, while the MAP method was suitable for the samples with x = 0.3 and 0.4. Among the Ising, XY, Heisenberg, and mean-field models, the samples with x = 0.2, 0.3, and 0.4 aligned more closely with the mean-field model, except for the x = 0.5 sample. Entropy change (−ΔSM) of Nd1−xSrxMnO3 (0.2 ≤ x ≤ 0.5) increased with the applied field, with the maximum value observed around TC. For the sample with x = 0.3, (−ΔSM) reached 4.315 J/kg K at μ0ΔH = 50 kOe, corresponding to a relative cooling power (RCP) of 280.48 J/kg. Remarkably, the x = 0.4 sample displayed (−ΔSM) of 3.298 J/kg K at μ0ΔH = 50 kOe near room temperature, with the RCP of 283.64 J/kg. These findings underscore the role of Sr doping in tuning the magnetic properties, critical behavior, and magnetocaloric effect of NdMnO3.

Nanostructural Modification of Fe2O3 Nanoparticles: Carbon Coating for Enhanced Magnetic Behavior

In this study, the enhancement of magnetic properties in Fe2O3 nanoparticles through nanostructural modification via carbon coating is investigated. Fe2O3 and carbon‐coated Fe2O3 nanoparticles are synthesized using the solvothermal method. Structural, morphological, optical, and magnetic properties are comprehensively analyzed. The results demonstrate a significant reduction in particle size upon carbon coating, effectively mitigating agglomeration. Furthermore, carbon‐coated nanoparticles exhibit substantial enhancement in coercivity, remanence, and saturation magnetization suggesting improved magnetic behavior in comparison to their uncoated counterparts. This enhancement is attributed to the prevention of spin misalignment at the nanoparticle surface by the carbon coating, as well as the formation of distinct magnetic domains due to the reduced particle size. The observed improvements underscore the effectiveness of carbon coating in tailoring the magnetic properties of Fe2O3 nanoparticles for applications in magnetic devices and biomedical systems, such as magnetic hyperthermia and drug delivery systems, where precise control over magnetic behavior is crucial.

Effect of SiO2 on structural, magnetic, and nonlinear optical behavior of cobalt ferrite nanoparticles

CoFe2O4 and CoFe2O4/SiO2 were synthesized by sol-gel method. The studies carried out using XRD, FT-IR, SEM, TEM, VSM, UV–Vis DRS, and Z-scan techniques. The CoFe2O4 has the inverse cubic spinal structure. TEM and SEM confirmed the less crystallite size of CoFe2O4/SiO2 nanocomposite than CoFe2O4. The results show that two samples have a pure single phase cobalt ferrite with face-centred cubic spinel phase. SiO2 matrix in CoFe2O4 nanocomposite results in reduction particle size and magnetic properties as well as enhancement band gap. The band-gap energy of CoFe2O4 and CoFe2O4/SiO2 calculated 1.76 and 1.92 eV, respectively. Our findings in nonlinear optical aspects suggest that the distinctive characteristics of CoFe2O4/SiO2 present opportunities for advancements in telecommunications and other related fields.