Dc Magnetic Properties Research Articles

Control of the geometry and anisotropy driven by the combination of steric and anion coordination effects in CoII complexes with N6-tripodal ligands: the impact of the size of the ligand on the magnetization relaxation time.

Four mononuclear CoII complexes of formula [Co(L)(SCN)2(CH3OH)0.5(H2O)0.5]·1.5H2O·0.75CH3OH (1), [Co(L1)Cl2]·H2O·2CH3CN (2), [Co(L1)(SCN)2]·1.5H2O·CH3OH (3) and [Co(L1)]ClO4·2CH3OH (4) were prepared from the N6-tripodal Schiff base ligands (S)P[N(Me)NC(H)2-Q]3 (L) and (S)P[N(Me)NC(H)1-ISOQ]3 (L1), where Q and ISOQ represent quinolyl and isoquinolyl moieties, respectively. In 1, the L ligand does not coordinate to the CoII ion in a tripodal manner but using a new N,N,S tridentate mode, which is due to the fact that the N6-tripodal coordination promotes a strong steric hindrance between the quinolyl moieties. However, L1 can coordinate to the CoII ions either in a tripodal manner using CoII salts with poorly coordinating anions to give 4 or in a bisbidentate fashion using CoII salt-containing medium to strongly coordinating anions to afford 2 and 3. In the case of L1, there is no steric hindrance between ISOQ moieties after coordination to the CoII ion. The CoII ion exhibits a distorted octahedral geometry for compounds 1-3, with the anions in cis positions for the former and in trans positions for the two latter compounds. Compound 4 shows an intermediate geometry between an octahedral and trigonal prism but closer to the latter one. DC magnetic properties, HFEPR and FIRMS measurements and ab initio calculations demonstrate that distorted octahedral complexes 1-3 exhibit easy-plane magnetic anisotropy (D > 0), whereas compound 4 shows large easy-axis magnetic anisotropy (D < 0). Comparative analysis of the magneto-structural data underlines the important role that is played not only by the coordination geometry but also the electronic effects in determining the anisotropy of the CoII ions. Compounds 2-3 show a field-induced slow relaxation of magnetization. Despite its large easy-axis magnetic anisotropy, compound 4 does not show significant slow relaxation (SMR) above 2 K under zero applied magnetic fields, but its magnetic dilution with ZnII triggers SMR at zero field. Finally, it is worth remarking that compounds 2-4 show smaller relaxation times than the analogous complexes with the tripodal ligand bearing in its arms pyridine instead of isoquinoline moieties, which is most likely due to the increase of the molecular size in the former one.

Effect of Powder Particle Surface Treatment on DC Magnetic Properties of Compacted Iron Cores

Effect of Powder Particle Surface Treatment on DC Magnetic Properties of Compacted Iron Cores

Impact of Twin's Landscape on the Magnetic Damping of La2/3Sr1/3MnO3 Thin Films

AbstractUnderstanding the origin and mechanisms of magnetic damping in complex oxide materials is crucial for optimizing spin dynamics and tailoring their properties for specific spintronic applications. Ferromagnetic resonance spectroscopy (FMR) technique has been used to investigate the magnetic damping of multiple La2/3Sr1/3MnO3 (LSMO) epitaxial thin films with similar thickness and identical DC magnetic properties. However, the dynamic magnetic properties exhibit noticeable variations among samples. Microstructural analyses using X‐ray diffraction (XRD) and atomic force microscopy (AFM), confirm that the samples are structurally identical, except for minute differences in the miscut angles of the substrates. Nevertheless, when examining the samples using backscattered electron (BSE) images in scanning electron microscopy (SEM), significant disparities in the twin distribution are observed. These variations in the twin distribution directly correlate with the observed differences in the damping values. A careful image analysis of BSE images allows to demonstrate that the increase of damping is due to the pinning of the magnetization in the twin boundaries.

Enhanced DC electrical resistivity and magnetic properties of transition metal cobalt substituted spinel MgFe2O4 ferrite system

Cobalt-substituted magnesium ferrite materials, denoted as Mg1-xCoxFe2O4 (with × = 0.0, 0.25, 0.5, and 0.75), were synthesized using the solid-state reaction method at 1200 °C. This study aimed to investigate these ferrite systems' morphology, structure, DC electrical resistivity, and magnetic characteristics. Various analytical techniques, including X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), Fourier-transform infrared (FT-IR) spectroscopy, DC electrical resistivity measurements, and vibrating sample magnetometer (VSM), were employed to assess the phase purity, microstructure, elemental composition, functional groups, resistivity, activation energy, and magnetic properties of the ferrite particles. The XRD patterns revealed a spinel cubic structure with the Fd3m space group. SEM images exhibited a few agglomerations and grains with spherical and polyhedral shapes, measuring 1.5 to 2 µm. The FTIR spectrum displayed two wavebands (ν1 and ν2) in the range of 400 cm−1 to 600 cm−1, corresponding to the lattice's tetrahedral and octahedral sites. Activation energies, which increased with higher cobalt concentrations, were calculated from DC electrical resistivity measurements. Furthermore, saturation magnetization and coercivity values gradually increased with rising cobalt concentrations.

Structural and magnetic properties of superconductive YFeSb1.2 compound

The structural and magnetic analysis of the YFeSb[Formula: see text] compound synthesized by the solid-state reaction method was observed. At room temperature, the compound exhibits the ThCr2Si2-type structure with the space group of [Formula: see text]. Low-field DC magnetic susceptibility property of the YFeSb[Formula: see text] compound has been examined. An obvious oscillation of the remanent magnetization, [Formula: see text] with temperature was observed. The YFeSb[Formula: see text] compound exhibits large irreversibility at low fields below the coercivity fields due to freezing spins at low temperatures. At higher temperatures, the susceptibility obeys perfectly to modified Curie–Weiss behavior. Each magnetic ion on a microscopic scale and each magnetic cluster on a nanoscale experience reveal a local random anisotropy.

Wide induction range analysis of DC magnetic properties and magnetization processes of Fe-based soft magnetic composites

The paper presents systematic analyses of a wide maximum induction range (0.001 T–1.4 T) DC magnetic properties of iron-based soft magnetic composite (SMC) materials by applying different methods to understand the specific features of magnetization reversal of this increasingly popular class of soft magnetic materials, including a hitherto less explored area of the Rayleigh region of very low magnetic fields, which has growing application potential in new, low-energy consuming electronic devices or ultra-low magnetic field shielding. The total permeability, coercive field and remanent magnetic induction were analysed in connection with the reciprocity factor and inner demagnetization factor and their relations to interparticle magnetic interaction, domain wall movability and predominance of individual magnetization processes. Their dependence on the magnetic induction and the properties of each sample were revealed and confirmed also by energy loss separation. The Rayleigh region analytical expressions for the coercive field, remanent magnetic induction, the ratio of irreversible to reversible magnetization changes and their percentages within the magnetizing cycle were used for SMCs for the first time.

Electric and Magnetic Properties of the Multiferroic Composites Made Based on Pb(Fe1/2Nb1/2)1-xMnxO3 and the Nickel-Zinc Ferrite.

This work presents the electrophysical properties of the multiferroic ceramic composites obtained as a result of combining both magnetic and ferroelectric material. The ferroelectric components of the composite are materials with the following chemical formulas: PbFe0.5Nb0.5O3 (PFN), Pb(Fe0.495Nb0.495Mn0.01)O3 (PFNM1), and Pb(Fe0.49Nb0.49Mn0.02)O3 (PFNM2), while the magnetic component of the composite is the nickel-zinc ferrite (Ni0.64Zn0.36Fe2O4 marked as F). The crystal structure, microstructure, DC electric conductivity, and ferroelectric, dielectric, magnetic, and piezoelectric properties of the multiferroic composites are performed. The conducted tests confirm that the composite samples have good dielectric and magnetic properties at room temperature. Multiferroic ceramic composites have a two-phase crystal structure (ferroelectric from a tetragonal system and magnetic from a spinel structure) without a foreign phase. Composites with an admixture of manganese have a better set of functional parameters. The manganese admixture increases the microstructure's homogeneity, improves the magnetic properties, and reduces the electrical conductivity of composite samples. On the other hand, in the case of electric permittivity, a decrease in the maximum values of εm is observed with an increase in the amount of manganese in the ferroelectric component of composite compositions. However, the dielectric dispersion at high temperatures (associated with high conductivity) disappears.

Measurement and Analysis of Magnetic Properties of Permalloy for Magnetic Shielding Devices under Different Temperature Environments.

The relative permeability, coercivity, and remanence of permalloy are closely related to the performance of magnetic shielding devices. In this paper, the relationship between the magnetic properties of permalloy and the working temperature of magnetic shielding devices is measured. Firstly, the measurement method of permalloy properties based on the simulated impact method is analyzed. What is more, a magnetic property test system consisting of a soft magnetic material tester and a high-low temperature chamber for permalloy ring samples at different temperatures was established to measure DC and AC (0.01 Hz to 1 kHz) magnetic properties at different temperatures (-60 °C to 140 °C). Finally, the results show that compared with room temperature (25 °C), the initial permeability (μi) decreases by 69.64% at -60 °C and increases by 38.23% at 140 °C, and the coercivity (hc) decreases by 34.81% at -60 °C and increases by 8.93% at 140 °C, which are the key parameters in the magnetic shielding device. It can be concluded that the relative permeability and remanence of permalloy are positively correlated with temperature, while the saturation magnetic flux density and coercivity are negatively correlated with temperature. This paper is of great significance to the magnetic analysis and design of magnetic shielding devices.

Cu2+ substituted Mg-Co ferrite has improved dc electrical resistivity and magnetic properties

Cu2+ substituted Mg-Co ferrite has improved dc electrical resistivity and magnetic properties

Soft magnetic composites based on Fe fibres and powders prepared by cold sintering process

The manuscript provides a new strategy for preparation of soft magnetic composites that involves the consolidation of the ferromagnetic phase (fibres or powders), which is first covered with an insulating layer, via the cold sintering process. The manuscript reports on the preparation and characterisation of cold sintered compacts based on Fe fibres and Fe powders coated with ZnO and sintered at the temperature of 200 °C for 60 min under the pressure of 600 MPa. The amount of ZnO used as dielectric phase was 10 and 20 wt%. The absence of any reaction between phases that compose the compacts (Fe fibres or powders and ZnO) during the cold sintering process was proved by X-ray diffraction (XRD). Electron microscopy and X-ray micro-analysis (SEM-EDX) were used for morphology and chemical analysis of the cold sintered compacts. The influence of the type of ferromagnetic phase (fibres or particles), as well as the influence of the amount of dielectric phase on the saturation induction (Bs), the coercive field (Hc), and the maximum relative permeability (µrmax) of the cold sintered magnetic cores, was investigated and discussed. The effect of the same factors on the total core power losses (P) and the initial relative permeability (µri) of the cold sintered compacts, upon increasing the frequency of the magnetising field up to 10 kHz, was analysed. The feasibility of applying a heat treatment at the temperature of 450 °C for 1 h was investigated, leading to the enhancement of both DC and AC magnetic properties of the cold sintered compacts.

X-ray structure and magnetic properties of a mononuclear complex and a 1D coordination polymer assembled by cobalt(II) ions and a flexible oxamate ligand

This work describes the synthesis, crystal structures and direct current (dc) magnetic properties of two air-stable oxamato-containing cobalt(II) complexes, [Co(H2edpba)(dmso)2]·dmso·H2O (1) and [Co(H2edpba)(H2O)2] n ·n(dmso) (2) [H4edpba = N,N′-2,2′-ethylenediphenylenebis(oxamic acid); dmso = dimethylsulfoxide]. 1 is a mononuclear compound, whereas 2 is a neutral chain. Cobalt(II) ions in both compounds are six-coordinate by six oxygen atoms, four of them from two monodeprotonated oxamate groups and the other two from dmso (1)/water (2) molecules in cis (1) and trans (2) positions. Hydrogen bonds between monodeprotonated oxamate fragments of adjacent mononuclear units in 1 lead to a supramolecular chain growing along the crystallographic c axis. Hydrogen bonds involving coordinated water molecules and monodeprotonated oxamate fragments from adjacent chains in 2 result in a supramolecular 2D network. Cryomagnetic measurements reveal the occurrence of magnetically isolated high-spin cobalt(II) ions in agreement with the large values of the shortest intramolecular (1)/intrachain (2) metal···metal separation [ca. 10.3 (1) and 10.4 Å (2)]. Simultaneous simulation of the χ M T versus T and M against H data through the Griffith–Figgis Hamiltonian led to the best-fit parameters: λ = −141.1 (1)/–174.8 cm−1 (2), σ = −1.45 (1)/–1.25 (2) and ν = −121.42 (1)/−247.29 cm−1 (2).

Probing the dc electrical resistivity and magnetic properties of mixed metal oxides Cr3+ substituted Mg–Zn ferrites

Probing the dc electrical resistivity and magnetic properties of mixed metal oxides Cr3+ substituted Mg–Zn ferrites

Effect of Sm3+ substitution on dc electrical resistivity and magnetic properties of Ni–Co ferrites

Sm3+ substituted Ni–Co ferrite materials have been developed with the chemical compositions Ni0.5Co0.5Fe2-xSmxO4 for x = 0.0, 0.02, 0.04, and 0.06 by solid-state method. A spinel with a single-phase cubic structure was found through XRD analysis. Crystallite size and lattice parameter fluctuation with Samarium content, decreasing with Sm3+ doping. When Sm3+ is doped, SEM shows a uniform distribution of grains with increasing agglomeration, and the grain size decreases with samarium concentration. Two peaks of absorption mode FTIR spectra show their spinel nature. The samples' negative temperature coefficient measured by the two probe method indicates their semiconducting nature. The DC electrical resistivity of the Ni–Co ferrite system was found to increase from 5.99 × 103 (Ω-cm) to 9.89 × 109 (Ω-cm) as an increase in Sm concentration. VSM measurement gives the saturation magnetization for the concentration up to x = 0.04 decreased and then increased for x = 0.06. All these properties show our samples' higher applicability in various electronic devices.

Structural and magnetic properties of flaky FeSiB/Al2O3 soft magnetic composites with orientation of a magnetic field

In this paper, flaky FeSiB/Al2O3 soft magnetic composites (SMCs) were prepared with the parallel or perpendicular orientation of an external magnetic field. The results showed that anisotropic structures were formed in FeSiB/Al2O3 SMCs, which can be attributed to the response of flaky particles with high shape anisotropy to the external magnetic field. For the parallel FeSiB/Al2O3 SMC, the particle plane of flaky FeSiB was parallelled to the working magnetic circuit, which further affected the easy axis, air gap length, demagnetizing field, and magnetic reluctance. The resulting DC and AC magnetic properties, such as saturation magnetization, effective permeability, complex permeability, energy loss, and frequency stability of permeability were all distinctly optimized.

Effect of Ni2+ substitution on DC electrical conductivity and magnetic properties of Ba1-xNixFe2O4 synthesized by citric acid gel method

The synthesis of Ba1-xNixFe2O4 (with x = 0.04, 0.08, 0.12) spinel ferrites were carried out by citric acid gel combustion method. Effect of Ni2+ substitution in Ba1-xNixFe2O4 ferrite lattice on its structural, magnetic, optical and electrical properties has been investigated by using XRD, FT-IR, VSM, UV-Vis.-DRS and DC electrical conductivity respectively. The single-phase orthorhombic spinel structure XRD results were confirmed with Pmcn space group. Decrease in lattice constant and unit cell volume is observed with the increase in Ni content. IR spectroscopy confirmed the existence of metal oxygen vibrations. M−H loops from VSM studies attributed the magnetization ranging from 0.1483 to 5.5969 emu/g and drastic changes in coercivity from 1220 to 2633 Oe is observed. Optical analysis and DC conductivity attributed decrease in band gap energy as well as activation energy respectively.

Paramagnetic 7Li NMR Shifts and Magnetic Properties of Divalent Transition Metal Silylamide Ate Complexes [LiM{N(SiMe3)2}3] (M2+ = Mn, Fe, Co).

7Li NMR shifts and magnetic properties have been determined for three so-called ate complexes [LiM{N(SiMe3)2}3] (M2+ = Mn, Fe, Co; e.g., named lithium-tris(bis(trimethylsilylamide))-manganate(II) in accordance with a formally negative charge assigned to the complex fragment [M{N(SiMe3)2}3]-, which comprises the transition metal). They are formed by addition reactions of LiN(SiMe3)2 and [M{N(SiMe3)2}2] and stabilized by Lewis base/Lewis acid interactions. The results are compared to those of the related "ion-separated" complexes [Li(15-crown-5)][M{N(SiMe3)2}3]. The ate complexes with the lithium atoms connected to the 3d metal atoms manganese, iron, or cobalt via μ2 nitrogen bridges reveal strong 7Li NMR paramagnetic shifts of about -75, 125, and 171 ppm, respectively, whereas the shifts for the lithium ions coordinated by the 15-crown-5 ether are close to zero. The observed trends of the 7Li NMR shifts are confirmed by density-functional theory calculations. The magnetic dc and ac properties display distinct differences for the six compounds under investigation. Both manganese compounds, [LiMn{N(SiMe3)2}3] and [Li(15-crown-5)][Mn{N(SiMe3)2}3], display almost pure and ideal spin-only paramagnetic behavior of a 3d5 high-spin complex. In this respect slightly unexpected, both complexes show slow relaxation behavior at low temperatures under applied dc fields, which is especially pronounced for the ate complex [LiMn{N(SiMe3)2}3]. Dc magnetic properties of the iron complexes reveal moderate g-factor anisotropies with small values of the axial magnetic anisotropy parameter D and a larger E (transversal anisotropy). Both complexes display at low temperatures and, under external dc fields of up to 5000 Oe, only weak ac signals with no maxima in the frequency range from 1 to 1500 s-1. In contrast, the two cobalt complexes display strong g-factor anisotropies with large values of D and E. In addition, in both cases, the ac measurements at low temperatures and applied dc fields reveal two, in terms of their frequency range, well separated relaxation processes with maxima lying for the most part outside of the measurement range between 1 and 1500 s-1.

A Series of Novel Pentagonal-Bipyramidal Erbium(III) Complexes with Acyclic Chelating N3O2 Schiff-Base Ligands: Synthesis, Structure, and Magnetism.

A series of six seven-coordinate pentagonal-bipyramidal (PBP) erbium complexes, with acyclic pentadentate [N3O2] Schiff-base ligands, 2,6-diacetylpyridine bis-(4-methoxybenzoylhydrazone) [H2DAPMBH], or 2,6-diacethylpyridine bis(salicylhydrazone) [H4DAPS], and various apical ligands in different charge states were synthesized: [Er(DAPMBH)(C2H5OH)Cl] (1); [Er(DAPMBH)(H2O)Cl]·2C2H5OH (2); [Er(DAPMBH)(CH3OH)Cl] (3); [Er(DAPMBH)(CH3OH)(N3)] (4); [(Et3H)N]+[Er(H2DAPS)Cl2]− (5); and [(Et3H)N]+[Y0.95Er0.05(H2DAPS)Cl2]− (6). The physicochemical properties, crystal structures, and the DC and AC magnetic properties of 1–6 were studied. The AC magnetic measurements revealed that most of Compounds 1–6 are field-induced single-molecule magnets, with estimated magnetization energy barriers, Ueff ≈ 16–28 K. The experimental study of the magnetic properties was complemented by theoretical analysis based on ab initio and crystal field calculations. An experimental and theoretical study of the magnetism of 1–6 shows the subtle impact of the type and charge state of the axial ligands on the SMM properties of these complexes.

Facile Synthesis, Static, and Dynamic Magnetic Characteristics of Varying Size Double-Surfactant-Coated Mesoscopic Magnetic Nanoparticles Dispersed Stable Aqueous Magnetic Fluids.

The present work reports the synthesis of a stable aqueous magnetic fluid (AMF) by dispersing double-surfactant-coated Fe3O4 magnetic nanoparticles (MNPs) in water using a facile ambient scalable wet chemical route. MNPs do not disperse well in water, resulting in low stability. This was improved by dispersing double-surfactant (oleic acid and sodium oleate)-coated MNPs in water, where cross-linking between the surfactants improves the stability of the AMFs. The stability was probed by rheological measurements and all the AMF samples showed a good long-term stability and stability against a gradient magnetic field. Further, the microwave spin resonance behavior of AMFs was studied in detail by corroborating the experimental results obtained from the ferromagnetic resonance (FMR) technique to theoretical predictions by appropriate fittings. A broad spectrum was perceived for AMFs which indicates strong ferromagnetic characteristics. The resonance field shifted to higher magnetic field values with the decrease in particle size as larger-size MNPs magnetize and demagnetize more easily since their magnetic spins can align in the field direction more definitely. The FMR spectra was fitted to obtain various spin resonance parameters. The asymmetric shapes of the FMR spectra were observed with a decrease in particle sizes, which indicates an increase in relaxation time. The relaxation time increased with a decrease in particle sizes (sample A to D) from 37.2779 ps to 42.8301 ps. Further, a detailed investigation of the structural, morphological, and dc magnetic properties of the AMF samples was performed. Room temperature dc magnetic measurements confirmed the superparamagnetic (SPM) characteristics of the AMF and the M-H plot for each sample was fitted with a Langevin function to obtain the domain magnetization, permeability, and hydrodynamic diameter of the MNPs. The saturation magnetization and coercivity of the AMF samples increased with the increase in dispersed MNPs’ size of the samples. The improvement in the stability and magnetic characteristics makes AMFs suitable candidates for various biomedical applications such as drug delivery, magnetic fluid hyperthermia, and biomedicines.

Screen-Printable, Self-Biased SrM/PDMS Composites for Integrated Magnetic Microwave Devices

This work introduces a material and method for high-volume, low-temperature, screen printing of self-biased magnetic films made from a composite of M-type strontium ferrite SrFe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">12</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">19</sub> (SrM) particles and polydimethylsiloxane (PDMS). The magnetic particles are aligned under a dc magnetic field, while the PDMS is cured at 75 °C, making this fabrication process compatible with semiconductor and printed-circuit-board substrates. Aligned composites with estimated SrM particle volume percentages of 14 vol.%, 20 vol.%, and 27 vol.% are fabricated, as well as an unaligned 14 vol.% composite for comparison. X-ray diffraction (XRD) and scanning electron microscopy (SEM) are used to examine the structure and composition of the composites. Furthermore, vibrating sample magnetometer and ferromagnetic resonance (FMR) measurements are performed to determine their dc and ac magnetic properties. Results show that the aligned composites have magnetic textures between 1.47 and 1.95, crystalline anisotropies between 1860 and 1960 kA/m, FMR frequencies of 45.5–45.9 GHz, and FMR linewidths between 3400 and 3500 Oe, indicating the potential for these materials in self-biased, non-reciprocal device applications. The analysis identifies that increased particle loading and better particle alignment may further improve these films by decreasing the linewidth.

Ironsand (Titanomagnetite-Titanohematite): Chemistry, Magnetic Properties and Direct Applications for Wireless Power Transfer.

Ironsand is an abundant and inexpensive magnetic mineral resource. However, the magnetic properties of unprocessed ironsand are often inadequate for any practical applications. In this work, the applicability of ironsand for use as a component in a soft magnetic composite for large-scale inductive power transfer applications was investigated. After magnetic separation, the chemical, structural and magnetic properties of ironsand sourced from different locations were compared. Differences observed in the DC magnetic properties were consistent with changes in the chemical compositions obtained from X-ray Absorption Near-Edge Spectroscopy (XANES), which suggests varying the titanohematite to titanomagnetite content. Increased content in titanomagnetite and magnetic permeability correlated well with the total Fe content in the materials. The best-performing ironsand with the highest permeability and lowest core losses was used alongside Mn,Zn-Ferrite particles (ranging from ∼100 m to 2 mm) to fabricate toroid cores with varying magnetic material loading. It was shown that ironsand can be used to replace up to 15 wt.% of the magnetic materials with minimal impact on the composite magnetic performance, thus reducing the cost. Ironsand was also used as a supporting material in a single-rail wireless power transfer system, effectively increasing the power transfer, demonstrating potential applications to reduce flux leakage.