Magnetochemistry

16 pages, 5037 KiB

Open AccessArticle

Enhancing Magnetic Performance of FeNi₅₀ Soft Magnetic Composites with Double-Layer Insulating Coating for High-Frequency Applications

by Weizhong Zheng, Zixin Zhou, Rongyu Zou and Minghui Yang

Magnetochemistry 2024, 10(7), 45; https://doi.org/10.3390/magnetochemistry10070045 (registering DOI) - 29 Jun 2024

Abstract

Soft magnetic composites (SMCs) such as FeNi₅₀ are indispensable in modern electronics due to their high magnetic permeability and low-loss characteristics, meeting the requirements for miniaturization and high-frequency operation. However, the integration of organic materials, initially aimed at reducing the total losses, [...] Read more.

Soft magnetic composites (SMCs) such as FeNi₅₀ are indispensable in modern electronics due to their high magnetic permeability and low-loss characteristics, meeting the requirements for miniaturization and high-frequency operation. However, the integration of organic materials, initially aimed at reducing the total losses, presents challenges by introducing thermal stability issues at high frequencies. To overcome this obstacle, we propose a double-layer insulating coating method, applying a complete inorganic/organic composite insulation layer to the surface of iron–nickel magnetic powder. The double-layer insulating coating insulation method aims to reduce the total losses, particularly the eddy-current losses prevalent in SMCs. Additionally, the double-layer insulating coating method helps alleviate the thermal stability issues associated with organic materials at high frequencies, ultimately enhancing the magnetic properties of SMCs. We systematically investigated the influence of different resin types on the microstructure of the double-layer insulating coating, accompanied by a comprehensive comparison of the magnetic properties of the resulting samples. The experimental findings demonstrate a significant reduction in the eddy-current losses through the double-layer insulating coating method, with the total losses decreasing by over 95% compared to the initial FeNi₅₀ magnetic powder composite (MPC) materials. Notably, the sodium silicate and silicone resins exhibited superior performances as double-layer insulating coatings, achieving total loss reductions of 1350 W/kg and 1492 W/kg, respectively. In conclusion, the double-layer insulating coating method addresses the challenges related to the total losses and thermal stability in SMCs, offering a promising approach to improve their performance in various electrical and electronic applications. Full article

17 pages, 4570 KiB

Open AccessArticle

One-Step Preparation Method and Rapid Detection Implementation Scheme for Simple Magnetic Tagging Materials

by **anxiao Song, Weiting Ma, ** Song and Hongying Wang

Magnetochemistry 2024, 10(7), 44; https://doi.org/10.3390/magnetochemistry10070044 - 22 Jun 2024

Abstract

With the widespread application of tagging materials, existing chemical tagging materials exhibit limitations in stability and detection under field conditions. This study introduces a novel magnetic detection scheme. Hydrophilic material-modified Fe₃O₄ nanoparticles (COOH-PEG@Fe₃O₄ NPs) were synthesized using [...] Read more.

With the widespread application of tagging materials, existing chemical tagging materials exhibit limitations in stability and detection under field conditions. This study introduces a novel magnetic detection scheme. Hydrophilic material-modified Fe₃O₄ nanoparticles (COOH-PEG@Fe₃O₄ NPs) were synthesized using the co-precipitation technique. The content of Fe₃O₄ nanoparticles in the magnetic tagging liquid can reach up to 10 wt% and remain stable in an aqueous phase system for seven days. This research details the preparation process, the characterization methods (IR, ¹HNMR, EDX, XRD, SEM, TEM, VSM, DLS), and the performance effects of the materials in magnetic tagging. Experimental results indicate that COOH-PEG@Fe₃O₄ NPs exhibit high remanence intensity (Br = 1.75 emu/g) and considerable stability, making it possible to quickly detect tagged liquids in the field using portable flux meters and optical pump magnetometers. This study provides new insights into the design and application of magnetic tagging materials, making it particularly suitable for long-term tagging and convenient detection in field scenarios. Full article

(This article belongs to the Section Applications of Magnetism and Magnetic Materials)

7 pages, 2284 KiB

Open AccessArticle

Bipolar Nb₃Cl₈ Field Effect Transistors

by Yixiang Lu, Kai Zhao, Tongyao Zhang and Baojuan Dong

Magnetochemistry 2024, 10(6), 43; https://doi.org/10.3390/magnetochemistry10060043 - 14 Jun 2024

Abstract

Field effect transistors based on few-layered van der Waals transition metal halide (TMH) Nb₃Cl₈ are studied in this work. Few-layered Nb₃Cl₈ exhibits typical N-type semiconducting behavior controlled by a Si gate, with the electrical signal enhancing as [...] Read more.

Field effect transistors based on few-layered van der Waals transition metal halide (TMH) Nb₃Cl₈ are studied in this work. Few-layered Nb₃Cl₈ exhibits typical N-type semiconducting behavior controlled by a Si gate, with the electrical signal enhancing as the thickness increases from 4.21 nm to 16.7 nm. Moreover, we find that the tunability of few-layered Nb₃Cl₈ FETs’ electrical transport properties can be significantly augmented through the use of an ionic liquid gate (or electrical double layer, EDL). This enhancement leads to a substantial increase in the on–off ratio by approximately a factor of

10^{2}

, with the transfer curve modulated into a bipolar fashion. The emergence of such bipolar tunable characteristics in Nb₃Cl₈ FETs serves to enrich the electronic properties within the transition metal halide family, positioning Nb₃Cl₈ as a promising candidate for diverse applications spanning transistors, logic circuits, neuromorphic computing and spintronics. Full article

(This article belongs to the Special Issue Advances in Magnetic Two Dimensional Materials)

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24 pages, 9619 KiB

Open AccessArticle

Nonequivalent Antiferromagnetically Coupled Sublattices Induce Two-Step Spin-Crossover Transitions: Equilibrium and Nonequilibrium Aspects

by Valon Veliu, Orhan Yalçın, Songül Özüm and Rıza Erdem

Magnetochemistry 2024, 10(6), 42; https://doi.org/10.3390/magnetochemistry10060042 - 4 Jun 2024

Abstract

As a continuation to the previously published work (Yalçın et al. (2022)), we investigate the equilibrium and nonequilibrium properties of the spin-crossover systems, with a specific focus on the nonequivalent sublattice, and compare these properties with those of the equivalent sublattices. We used [...] Read more.

As a continuation to the previously published work (Yalçın et al. (2022)), we investigate the equilibrium and nonequilibrium properties of the spin-crossover systems, with a specific focus on the nonequivalent sublattice, and compare these properties with those of the equivalent sublattices. We used the lowest approximation of the cluster variation method (LACVM) to derive the static equations for the order parameters of the two sublattices and determine high-spin fraction in relation to temperature and external magnetic field in a spin-crossover system. At a low temperature, the transition from stable high-spin (HS) state where

n_{H S} = 1

occurs in the plateau region, where

n_{H S} = 0.5

for nonequivalent sublattices. The order parameters for non-equivalent sublattices exhibit different states at the transition temperature. Also, we study the nonequilibrium properties of the order parameters and high-spin fraction using the path probability method (PPM). With the current model, we obtain and analyze the relaxation curves for the order parameters

S_{a}

,

S_{b}

, and high-spin fraction. These curves demonstrate the existence of bistability at low temperatures. At the end of this study, we present the flow diagram that shows the order parameters for different temperature values. The diagram exhibits states that are stable, metastable, and unstable. Full article

(This article belongs to the Section Spin Crossover and Spintronics)

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13 pages, 2413 KiB

Open AccessArticle

Magnetically Induced Two-Phonon Blockade in a Hybrid Spin–Mechanical System

by Hong-Yue Liu, Tai-Shuang Yin and Aixi Chen

Magnetochemistry 2024, 10(6), 41; https://doi.org/10.3390/magnetochemistry10060041 - 31 May 2024

Abstract

Phonon blockade is an important quantum effect for revealing the quantum behaviors of mechanical systems. For a nitrogen-vacancy center spin strongly coupled to a mechanical resonator via the second-order magnetic gradient, we show that the qubit driving can lead to the implementation of [...] Read more.

Phonon blockade is an important quantum effect for revealing the quantum behaviors of mechanical systems. For a nitrogen-vacancy center spin strongly coupled to a mechanical resonator via the second-order magnetic gradient, we show that the qubit driving can lead to the implementation of the two-phonon blockade, while the usual mechanical driving only allows for the appearance of a single-phonon blockade. As a signature, we investigate three-phonon antibunching with a simultaneous two-phonon bunching process by numerically calculating the second-order and third-order correlation functions. We also analyze in detail the influence of the system parameters (including the qubit driving strength, the dephasing rate of the qubit, as well as the thermal phonon number) on the quality of the two-phonon blockade effect. Our work provides an alternative method for extending the concept of a phonon blockade from a single phonon to multiphonon. It is of direct relevance for the engineering of multiphonon quantum coherent devices and thus has potential applications in quantum information processing. Full article

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21 pages, 3233 KiB

Open AccessReview

The Catalytic Activity of Magnetic Surfaces

by Ian Shuttleworth

Magnetochemistry 2024, 10(6), 40; https://doi.org/10.3390/magnetochemistry10060040 - 28 May 2024

Abstract

High-performance catalysts for the oxygen reduction and hydrogen evolution reactions (ORR and HER, respectively) are highly sought-after, particularly with the commitment of numerous agencies to the removal of conventional gas vehicles in the next few decades. Surprisingly little focus has been placed on [...] Read more.

High-performance catalysts for the oxygen reduction and hydrogen evolution reactions (ORR and HER, respectively) are highly sought-after, particularly with the commitment of numerous agencies to the removal of conventional gas vehicles in the next few decades. Surprisingly little focus has been placed on the development of magnetic models to describe these systems. The current work will review the current understanding of surface heterogeneous catalysis across select magnetic surfaces, with attention focused on studies involving extended surfaces, which inherently are more accessible to fundamental analysis than the more applied nanoparticle systems. However, even the most up-to-date magnetic variants of this theory have focused on the tight binding limit of the d-band model. In this limit, the reactivity of the surface is governed by the position of the center of the d-band, and the model does not account for the higher moments of the d-band, such as the width, asymmetry, and modality. A summary of the theory supporting this analysis will be presented, along with a summary of the current literature on this level of analysis. The review will then conclude with a discussion of suggested directions for future investigations. Full article

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Graphical abstract

8 pages, 2225 KiB

Open AccessArticle

Magnetically Induced Near-Infrared Circularly Polarized Electroluminescence from an Achiral Perovskite Light-Emitting Diode

by Yoshitane Imai, Ryo Amasaki, Yoshihiko Yanagibashi, Seika Suzuki, Ryuta Shikura and Shigeyuki Yagi

Magnetochemistry 2024, 10(6), 39; https://doi.org/10.3390/magnetochemistry10060039 - 28 May 2024

Abstract

Circularly polarized electroluminescent devices are conventionally fabricated by incorporating an optically active chiral luminophore into their emission layer. Herein, we developed a circularly polarized perovskite light-emitting diode (PeLED) system with an optically inactive perovskite luminophore that can emit near-infrared circularly polarized electroluminescence (CPEL) [...] Read more.

Circularly polarized electroluminescent devices are conventionally fabricated by incorporating an optically active chiral luminophore into their emission layer. Herein, we developed a circularly polarized perovskite light-emitting diode (PeLED) system with an optically inactive perovskite luminophore that can emit near-infrared circularly polarized electroluminescence (CPEL) upon application of an external magnetic field. The magnitude of the magnetic CPEL (g_MCPEL) was in the order of 10⁻³ in the near-infrared wavelength range of 771–773 nm. Although the Pb perovskite quantum dots were achiral, the rotation direction of the CPEL of the magnetic circularly polarized PeLED system was successfully reversed by switching the Faraday geometry of the applied magnetic field. The use of achiral luminophores exhibiting magnetic-field-induced CPEL represents a new approach for the development of circularly polarized electroluminescent devices. Full article

(This article belongs to the Section Applications of Magnetism and Magnetic Materials)

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20 pages, 5977 KiB

Open AccessArticle

New Branched Iron(III) Complexes in Fluorescent Environment Created by Carbazole Moieties: Synthesis and Structure, Static Magnetic and Resonance Properties

by Denis V. Starichenko, Valerya E. Vorobeva, Matvey S. Gruzdev, Ulyana V. Chervonova, Nataliya G. Bichan, Aleksander V. Korolev and Ivan V. Yatsyk

Magnetochemistry 2024, 10(6), 38; https://doi.org/10.3390/magnetochemistry10060038 - 21 May 2024

Abstract

The branched complexes of Schiff bases with various iron(III) salts, named G2-[L₂Fe]⁺A⁻ (A⁻ is NO₃⁻, Cl⁻, PF₆⁻), were synthesized using the condensation reaction between carbazole derivatives of salicylic aldehyde [...] Read more.

The branched complexes of Schiff bases with various iron(III) salts, named G2-[L₂Fe]⁺A⁻ (A⁻ is NO₃⁻, Cl⁻, PF₆⁻), were synthesized using the condensation reaction between carbazole derivatives of salicylic aldehyde and N’-ethylethylenediamine and characterized by various spectroscopic methods (GPC, IR, ¹H NMR, UV/Vis). The studies revealed that the coordination of the two ligand molecules to metal occurs through the nitrogen ions and oxygen atom of azomethine to form a homoleptic system. All the synthesized coordination compounds were examined for their thermal, optical, and magnetic features. Static magnetic measurements showed that only G2-[L₂Fe]Cl was in a single-phase HS state, whereas the Fe(III) ions of G2-[L₂Fe]NO₃ and G2-[L₂Fe]PF₆ at room temperatures were in mixed low-spin (LS, S = 1/2) and high-spin (HS, S = 5/2) states: 58.9% LS/41.1% HS for G2-[L₂Fe]NO₃, 56.1% LS and 43.9% HS for G2-[L₂Fe]PF₆. All G2-[L₂Fe]⁺A⁻ complexes demonstrate antiferromagnetic exchange interactions between neighboring Fe(III) ions. The ground spin state at 2.0 K revealed a Brillouin contribution from non-interacting LS ions and a proportion of the HS Fe(III) ions not participating in AFM interactions: 57%, 18%, and 16% for G2-[L₂Fe]Cl, G2-[L₂Fe]NO₃ and G2-[L₂Fe]PF₆, respectively. EPR measurements confirmed the presence of magnetically active HS and LS states of Fe(III) ions and made it possible to distinguish two HS types-with strong low-symmetry (I-type) and weak, distorted octahedral environments (II-type). It was shown that G2-[L₂Fe]⁺A⁻ complexes are magnetically inhomogeneous and consist of two magnetic sub-lattices: AFM-correlated chains in layers from the I-type HS Fe(III) centers and dynamic short-range AFM ordered LS/II-type HS Fe(III) centers in the paramagnetic phase located between the layers. Full article

(This article belongs to the Special Issue Functional Magnetic Nanomaterials and Nanostructures: Properties and Applications)

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9 pages, 3012 KiB

Open AccessArticle

The Electric Properties of the Magnetopause Boundary Layer

by Lai Gao, Chao Shen, Yong Ji, Yufei Zhou and Yulia V. Bogdanova

Magnetochemistry 2024, 10(6), 37; https://doi.org/10.3390/magnetochemistry10060037 - 21 May 2024

Abstract

The magnetopause plays a pivotal role in the coupling among solar wind, the magnetosheath, and the magnetosphere. By analyzing magnetopause crossing events using MMS, we reveal a local non-neutrality of electric charges in the magnetopause boundary layer and the associated electric field. There [...] Read more.

The magnetopause plays a pivotal role in the coupling among solar wind, the magnetosheath, and the magnetosphere. By analyzing magnetopause crossing events using MMS, we reveal a local non-neutrality of electric charges in the magnetopause boundary layer and the associated electric field. There are two types of electric structures. In one group, which typically occurs on the dusk side, the electric field directs towards the Earth. In the other, which generally occurs on the day side, the field directs away from the Earth. The spatial extent of this electric non-neutrality spans approximately 600 km, which is at the scale of ion gyrational motion. These findings provide valuable insights into the fine structures of the magnetopause and the coupling between the magnetosheath and the magnetosphere. Full article

(This article belongs to the Special Issue New Insight into the Magnetosheath)

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8 pages, 2098 KiB

Open AccessArticle

Comparison of Current Induced Domain Wall Motion Driven by Spin Transfer Torque and by Spin Orbit Torque in Ferrimagnetic GdFeCo Wires

by Pham Van Thach, Satoshi Sumi, Kenji Tanabe and Hiroyuki Awano

Magnetochemistry 2024, 10(5), 36; https://doi.org/10.3390/magnetochemistry10050036 - 19 May 2024

Abstract

Current-induced domain wall motion (CIDWM) in magnetic wires can be driven by spin transfer torque (STT) originating from transferring angular momentums of spin-polarized conducting electrons to the magnetic DW and can be driven by spin orbit torque (SOT) originating from the spin Hall [...] Read more.

Current-induced domain wall motion (CIDWM) in magnetic wires can be driven by spin transfer torque (STT) originating from transferring angular momentums of spin-polarized conducting electrons to the magnetic DW and can be driven by spin orbit torque (SOT) originating from the spin Hall effect (SHE) in a heavy metal layer and Dzyaloshinsky Moriya (DMI) generated at an interface between a heavy metal layer and a magnetic layer. In this work, we carried out a comparative study of CIDWM driven by STT and by SOT in ferrimagnetic GdFeCo wires with magnetic perpendicular anisotropy based on structures of SiN (10 nm)/GdFeCo (8 nm)/SiN (10 nm) and Pt (5 nm)/GdFeCo (8 nm)/SiN (10 nm). We found that CIDWM driven by SOT exhibited a much lower critical current density (J_C), and much higher DW mobility (µ_DW). Our work might be useful for the realization and the development of low-power and high-speed memory devices. Full article

(This article belongs to the Special Issue Advances in Functional Materials with Tunable Magnetic Properties)

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27 pages, 11656 KiB

Open AccessArticle

Novel Hybrid Ferromagnetic Fe–Co/Nanodiamond Nanostructures: Influence of Carbon on Their Structural and Magnetic Properties

by Panagiotis G. Ziogas, Athanasios B. Bourlinos, Polyxeni Chatzopoulou, George P. Dimitrakopulos, Anastasios Markou and Alexios P. Douvalis

Magnetochemistry 2024, 10(5), 35; https://doi.org/10.3390/magnetochemistry10050035 - 17 May 2024

Abstract

This study introduces a novel magnetic nanohybrid material consisting of ferromagnetic (FM) bcc Fe–Co nanoparticles (NPs) grown on nanodiamond (ND) nanotemplates. A combination of wet chemistry, which produces chemical precursors and their subsequent thermal treatment under vacuum, was utilized for its development. The [...] Read more.

This study introduces a novel magnetic nanohybrid material consisting of ferromagnetic (FM) bcc Fe–Co nanoparticles (NPs) grown on nanodiamond (ND) nanotemplates. A combination of wet chemistry, which produces chemical precursors and their subsequent thermal treatment under vacuum, was utilized for its development. The characterization and study of the prepared samples performed with a range of specialized experimental techniques reveal that thermal treatment of the as-prepared hybrid precursors under a range of annealing conditions leads to the development of Co-rich Fe–Co alloy NPs, with average sizes in the range of 6–10 nm, that exhibit uniform distribution on the surfaces of the ND nanotemplates and demonstrate FM behavior throughout a temperature range from 2 K to 400 K, with maximum magnetization values ranging between 18.9 and 21.1 emu/g and coercivities ranging between 112 and 881 Oe. Moreover, ⁵⁷Fe Mössbauer spectroscopy reveals that apart from the predominant bcc FM Fe–Co phase, iron atoms also participate in the formation of a secondary martensitic-type Fe–Co phase. The emergence of this distinctive phase is attributed to the diffusion of carbon atoms within the Fe–Co lattices during their formation at elevated temperatures. The source of these carbon atoms is related to the unique morphological properties of the ND growth matrices, which facilitate surface sp² formations. Apart from their diffusion within the Fe–Co NP lattice, the carbon atoms also reconstruct layered graphitic-type nanostructures envelo** the metallic alloy NPs. These non-typical nanohybrid materials, reported here for the first time in the literature, hold significant potential for use in applications related, but not limited to, biomedicine, biopharmaceutics, catalysis, and other various contemporary technological fields. Full article

(This article belongs to the Section Magnetic Nanospecies)

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12 pages, 3422 KiB

Open AccessArticle

Tuning Structure and Properties of a Ferromagnetic Organic Semiconductor via a Magnetic Field-Modified Reduction Process

by Han Zhou, Zaitian Cheng, Zhiqiang Ai, **nyao Li, Lin Hu and Fapei Zhang

Magnetochemistry 2024, 10(5), 34; https://doi.org/10.3390/magnetochemistry10050034 - 15 May 2024

Abstract

The development of novel synthesis and assembly strategies is critical to achieving a ferromagnetic organic semiconductor with high Curie temperature. In this study, we report a high magnetic field (HMF)-modified solvothermal approach for the reduction in neutral perylene diimide (PDI) into the dianion [...] Read more.

The development of novel synthesis and assembly strategies is critical to achieving a ferromagnetic organic semiconductor with high Curie temperature. In this study, we report a high magnetic field (HMF)-modified solvothermal approach for the reduction in neutral perylene diimide (PDI) into the dianion species to prepare the PDI magnets comprising radical anions after subsequent oxidation processes. The PDI materials, assembled from the dianion solution by an HMF-modified reduction, exhibit a smaller crystallite size and an enlarged distance of the π-π stacking in the PDI aggregates. Furthermore, the PDI magnets obtained from the process under a 9T field reveal weakened ferromagnetism and the rapid degradation of electrical conductivity compared to those prepared without a magnetic field. Based on spectral and structural characterizations, such performance deterioration originates from the enhanced instability of the radical anions exposed to air, as well as the decreased crystallinity for the radical PDIs synthesized from the HMF-modified reduction process. This work demonstrates that magnetic fields offer an effective way in the material synthesis process to manipulate the structure and magnetic properties of the radical-based organic magnets. Full article

(This article belongs to the Special Issue Recent Progress of Magnetic Field Effect on Catalysts)

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14 pages, 4900 KiB

Open AccessArticle

Preparation of Magnetic Nano-Catalyst Containing Schiff Base Unit and Its Application in the Chemical Fixation of CO₂ into Cyclic Carbonates

by Na Kang, Yindi Fan, Dan Li, **aoli Jia and Sanhu Zhao

Magnetochemistry 2024, 10(5), 33; https://doi.org/10.3390/magnetochemistry10050033 - 26 Apr 2024

Abstract

The development of a catalyst for the conversion of CO₂ and epoxides to the corresponding cyclic carbonates is still a very attractive topic. Magnetic nano-catalysts are widely used in various organic reactions due to their magnetic separation and recycling properties. Here, a [...] Read more.

The development of a catalyst for the conversion of CO₂ and epoxides to the corresponding cyclic carbonates is still a very attractive topic. Magnetic nano-catalysts are widely used in various organic reactions due to their magnetic separation and recycling properties. Here, a magnetic nano-catalyst containing a Schiff base unit was designed, synthesized and used as a heterogeneous catalyst to catalyze CO₂ and epoxides to form cyclic carbonates without solvents and co-catalysts. The catalyst was characterized using Fourier transform infrared (FTIR), X-ray diffraction (XRD), thermogravimetric (TG), VSM, SEM, TEM and BET. The results show that the magnetic nano-catalyst containing the Schiff base unit has a high activity in the solvent-free cycloaddition reaction of CO₂ with epoxide under mild conditions, and is easily separated from the reaction mixture driven by external magnetic force. The recovered catalyst maintains a high performance after five cycles. Full article

(This article belongs to the Special Issue Recent Progress of Magnetic Field Effect on Catalysts)

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18 pages, 4269 KiB

Open AccessArticle

Relationship between Structure and Zero-Field Splitting of Octahedral Nickel(II) Complexes with a Low-Symmetric Tetradentate Ligand

by Hiroshi Sakiyama, Rin Kimura, Haruto Oomiya, Ryoji Mitsuhashi, Sho Fujii, Katsuhiko Kanaizuka, Mohd. Muddassir, Yuga Tamaki, Eiji Asato and Makoto Handa

Magnetochemistry 2024, 10(5), 32; https://doi.org/10.3390/magnetochemistry10050032 - 24 Apr 2024

Abstract

Octahedral nickel(II) complexes are among the simplest systems that exhibit zero-field splitting by having two unpaired electrons. For the purpose of clarifying the relationship between structure and zero-field splitting in a low-symmetric system, distorted octahedral nickel(II) complexes were prepared with a tetradentate ligand, [...] Read more.

Octahedral nickel(II) complexes are among the simplest systems that exhibit zero-field splitting by having two unpaired electrons. For the purpose of clarifying the relationship between structure and zero-field splitting in a low-symmetric system, distorted octahedral nickel(II) complexes were prepared with a tetradentate ligand, 2-[bis(2-methoxyethyl)aminomethyl]-4-nitrophenolate(1−) [(onp)⁻]. The complex [Ni(onp)(dmso)(H₂O)][BPh₄]·2dmso (1) (dmso = dimethyl sulfoxide) was characterized as a bulk sample by IR, elemental analysis, mass spectrometry, electronic spectra, and magnetic properties. The powder electronic spectral data were analyzed based on the angular overlap model to conclude that the spectra were typical of D₄-symmetric octahedral coordination geometry with a weak axial ligand field. Simultaneous analysis of the temperature-dependent susceptibility and field-dependent magnetization data yielded the positive axial zero-field splitting parameter D (H = g_uβS_uH_u + D[S_z² − S(S + 1)/3]), which was consistent with the weak axial ligand field. Single-crystal X-ray analysis revealed the crystal structures of [Ni(onp)(dmso)(H₂O)][BPh₄]·dmso (2) and [Ni(onp)(dmf)₂][BPh₄] (3) (dmf = N,N-dimethylformamide). The density functional theory (DFT) computations based on the crystal structures indicated the D₄-symmetric octahedral coordination geometries with weak axial ligand fields. This study also showed the importance of considering g-anisotropy in magnetic analysis, even if g-anisotropy is small. Full article

(This article belongs to the Section Molecular Magnetism)

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15 pages, 2255 KiB

Open AccessArticle

A Novel Magnetic Nano-Adsorbent Functionalized with Green Tea Extract and Magnesium Oxide to Remove Methylene Blue from Aqueous Solutions: Synthesis, Characterization, and Adsorption Behavior

by Wenchao Lin, Yaoyao Huang, Shuang Liu, Wei Ding, Hong Li and Huaili Zheng

Magnetochemistry 2024, 10(5), 31; https://doi.org/10.3390/magnetochemistry10050031 - 24 Apr 2024

Abstract

In this study, a novel green tea/Mg-functionalized magnetic nano-adsorbent, denoted as GTE-MgO-Fe₃O₄ NPs, was developed and applied to the extraction of Methylene Blue (MB) from water-based solutions. The GTE-MgO-Fe₃O₄ NPs were synthesized by incorporating green tea extracts [...] Read more.

In this study, a novel green tea/Mg-functionalized magnetic nano-adsorbent, denoted as GTE-MgO-Fe₃O₄ NPs, was developed and applied to the extraction of Methylene Blue (MB) from water-based solutions. The GTE-MgO-Fe₃O₄ NPs were synthesized by incorporating green tea extracts (GTE) and Mg species onto the surface of Fe₃O₄ nanoparticles using a hydrothermal method. Characterization analyses corroborated the successful functionalization of the Fe₃O₄ surface with GTE and Mg species, resulting in a superparamagnetic adsorbent equipped with abundant surface functional groups, which promoted MB adsorption and facilitated magnetic separation. Batch experiments revealed that different operating parameters had an impact on the adsorption behavior, such as adsorbent dosage, pH, coexisting ions, contact time, the initial MB concentration, and temperature. The investigations of adsorption kinetics and isotherms emphasized that the MB adsorption onto GTE-MgO-Fe₃O₄ NPs was an exothermic process dominated by chemisorption. The experimental adsorption capacity of GTE-MgO-Fe₃O₄ NPs for MB surpassed 174.93 mg g⁻¹, markedly superior to the performance of numerous other adsorbents. Ultimately, the utilized GTE-MgO-Fe₃O₄ NPs could be effectively regenerated through acid pickling, retaining over 76% of its original adsorption capacity after six adsorption–desorption cycles, which suggested that GTE-MgO-Fe₃O₄ NPs was a suitable adsorbent for eliminating MB from effluent. Full article

(This article belongs to the Special Issue Applications of Magnetic Materials in Water Treatment)

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14 pages, 16266 KiB

Open AccessArticle

The Piezoresistive Performance of CuMnNi Alloy Thin-Film Pressure Sensors Prepared by Magnetron Sputtering

by Zhengtao Wu, **aotao He, Yu Cao, Qimin Wang, Yisong Lin, Liangliang Lin and Chao Liu

Magnetochemistry 2024, 10(5), 30; https://doi.org/10.3390/magnetochemistry10050030 - 23 Apr 2024

Abstract

Effects of varying Mn and Ni concentrations on the structure and piezoresistive properties of CuMnNi films deposited by magnetron sputtering with a segmented target were investigated. An increase in the Ni content refines the CuNi film grains, inducing an increase in defects such [...] Read more.

Effects of varying Mn and Ni concentrations on the structure and piezoresistive properties of CuMnNi films deposited by magnetron sputtering with a segmented target were investigated. An increase in the Ni content refines the CuNi film grains, inducing an increase in defects such as internal micropores and a decrease in film density. At the same time, the positive piezoresistive coefficient of the film changes to negative. When 17.5 at.% Ni was added, the negative piezoresistive coefficient of the CuNi film was −2.0 × 10⁻⁴ GPa⁻¹. The do** of Ni has a weakening effect on the positive piezoresistive effect of the film. Adding Mn into Cu refines the film grains while increasing the film density. The surface roughness of the film decreases with the increase in Mn content. When the Mn content was 16.7 at.%, the piezoresistive coefficient reached the largest recorded value of 23.81 × 10⁻⁴ GPa⁻¹, and the film exhibited excellent repeatability in multiple piezoresistive tests. After the CuMn film with 16.7 at.% Mn was annealed at 400 °C for 2 h, the film grains grew slightly and the film residual stress decreased. The optimization of the film structure can reduce the scattering of electrons during transportation. The piezoresistive coefficient of the film was further improved to 35.78 × 10⁻⁴ GPa⁻¹. Full article

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18 pages, 4168 KiB

Open AccessArticle

Numerical Analysis of the Influence of a Magnetic Field on the Group Dynamics of Iron-Doped Carbon Nanotori

by Vladislav I. Borodin, Alexey M. Bubenchikov, Mikhail A. Bubenchikov, Dmitry S. Kaparulin and Vyacheslav A. Ovchinnikov

Magnetochemistry 2024, 10(4), 29; https://doi.org/10.3390/magnetochemistry10040029 - 18 Apr 2024

Abstract

Columnar phases consisting of a group of carbon toroidal molecules (C₁₂₀, C₁₉₂, C₂₅₂, C₂₈₈) are studied numerically. Each nanotorus was previously doped with an iron atom. This made it possible to use an external magnetic [...] Read more.

Columnar phases consisting of a group of carbon toroidal molecules (C₁₂₀, C₁₉₂, C₂₅₂, C₂₈₈) are studied numerically. Each nanotorus was previously doped with an iron atom. This made it possible to use an external magnetic field as a tool for influencing both an individual molecule and a linear fragment of the columnar phase. A high-precision scheme for calculating the dynamics of large molecules with a rigid frame structure is proposed to solve the problem. The group dynamics of nanotori clusters under the influence of an external magnetic field has been studied using classical molecular dynamics methods. The influence of the molecular cluster size, temperature, magnetic moment of the molecule, and magnetic field direction on the collective behavior of iron-doped toroidal molecules with different contents of carbon atoms is analyzed. Molecular dynamics calculations showed that systems of nanotori doped with a single iron atom retain a columnar structure both in the absence and in the presence of an external magnetic field. The columnar fragment behaves as a stable linear association of molecules even at sufficiently high values of magnetic induction, performing a coordinated collective orbital rotation around a common center of mass on a nanosecond time scale. Full article

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29 pages, 3853 KiB

Open AccessReview

Recent Advances in Magnetically Actuated Droplet Manipulation for Biomedical Applications

by Jiaqi Li, Kaixin Su, Hailan Liu and Yuan Zou

Magnetochemistry 2024, 10(4), 28; https://doi.org/10.3390/magnetochemistry10040028 - 16 Apr 2024

Abstract

The manipulation of droplets plays a vital role in biomedicine, chemistry, and hydromechanics, especially in microfluidics. Magnetic droplet manipulation has emerged as a prominent and advanced technique in comparison to other modes such as dielectric infiltration, optical radiation, and surface acoustic waves. Its [...] Read more.

The manipulation of droplets plays a vital role in biomedicine, chemistry, and hydromechanics, especially in microfluidics. Magnetic droplet manipulation has emerged as a prominent and advanced technique in comparison to other modes such as dielectric infiltration, optical radiation, and surface acoustic waves. Its notable progress is attributed to several advantages, including excellent biocompatibility, remote and non-contact control, and instantaneous response. This review provides a comprehensive overview of recent developments in magnetic droplet manipulation and its applications within the biomedical field. Firstly, the discussion involves an examination of the distinctive features associated with droplet manipulation based on both permanent magnet and electromagnet principles, along with a thorough exploration of the influencing factors impacting magnetic droplet manipulation. Additionally, an in-depth review of magnetic actuation mechanisms and various droplet manipulation methods is presented. Furthermore, the article elucidates the biomedical applications of magnetic droplet manipulation, particularly its role in diagnostic assays, drug discovery, and cell culture. Finally, the highlights and challenges of magnetic droplet manipulation in biomedical applications are described in detail. Full article

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2 pages, 494 KiB

Open AccessCorrection

Correction: Gautam et al. Experimental Thermal Conductivity Studies of Agar-Based Aqueous Suspensions with Lignin Magnetic Nanocomposites. Magnetochemistry 2024, 10, 12

by Bishal Gautam, Saja M. Nabat Al-Ajrash, Mohammad Jahid Hasan, Abhishek Saini, Sarah J. Watzman, Esteban Ureña-Benavides and Erick S. Vasquez-Guardado

Magnetochemistry 2024, 10(4), 27; https://doi.org/10.3390/magnetochemistry10040027 - 15 Apr 2024

Abstract

In the original publication [...] Full article

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Magnetochemistry

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