Magnetochemistry

4 pages, 179 KiB

Open AccessEditorial

Synthetic, Natural and Natural-Synthetic Hybrid Magnetic Structures: Technology and Application

by Kamil G. Gareev

Magnetochemistry 2024, 10(12), 92; https://doi.org/10.3390/magnetochemistry10120092 - 22 Nov 2024

The magnetic properties of various types of structures based on iron oxides and the other ferri- or ferromagnets strongly correlate with their origin [...] Full article

(This article belongs to the Special Issue Synthetic, Natural and Natural-Synthetic Hybrid Magnetic Structures: Technology and Application)

18 pages, 7841 KiB

Open AccessArticle

Macroscopic and Microscopic Levels of Methylene Blue Adsorption on a Magnetic Bio-Based Adsorbent: In-Depth Study Using Experiments, Advanced Modeling, and Statistical Thermodynamic Analysis

by Mohamed A. Ali, Aliaa M. Badawy, Ali Q. Seliem, Hazem I. Bendary, Eder C. Lima, M. Al-Dossari, N. S. Abd EL-Gawaad, Glaydson S. dos Reis, Mohamed Mobarak, Ali M. Hassan and Moaaz K. Seliem

Magnetochemistry 2024, 10(11), 91; https://doi.org/10.3390/magnetochemistry10110091 - 20 Nov 2024

Abstract

A magnetic bio-based adsorbent derived from H₂O₂-activated zeolite and turmeric carbohydrate polymer was fabricated, characterized, and utilized in removing methylene blue (MB) dye at pH 8.0 and temperatures between 25 and 55 °C. To understand the molecular-scale adsorption mechanism, [...] Read more.

A magnetic bio-based adsorbent derived from H₂O₂-activated zeolite and turmeric carbohydrate polymer was fabricated, characterized, and utilized in removing methylene blue (MB) dye at pH 8.0 and temperatures between 25 and 55 °C. To understand the molecular-scale adsorption mechanism, a range of advanced statistical physics models were employed in conjunction with conventional equilibrium models. The as-synthesized biosorbent presented high maximum capacities according to the Langmuir model, with values ranging from 268.67 to 307.73 mg/g. The double-layer equation yielded the best-fitting results to the MB experimental data among the applied statistical physics models. The number of MB molecules ranged from 1.14 to 1.97, suggesting a multi-molecular mechanism with a non-parallel orientation. The main factor affecting the effectiveness of this adsorbent was the density of its functional groups, which varied from 27.7 to 142.1 mg/g. Adsorption energies in the range of 19.22–21.69 kJ/mol were obtained, representing the existence of physical forces like hydrogen bonds and electrostatic interactions. To complete the macroscopic examination of the MB adsorption mechanism, thermodynamic parameters such as entropy, Gibbs free energy, and internal energy were considered. The adsorption/desorption outcomes up to five cycles displayed the stability of the magnetic biosorbent and its potential for decontaminating industrial effluents. Overall, this work increases our understanding of the MB adsorption mechanism onto the produced biosorbent at the molecular level. Full article

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

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23 pages, 1964 KiB

Open AccessReview

Recent Insights into Magneto-Structural Properties of Co(II) Dicyanamide Coordination Compounds

by Anna Świtlicka

Magnetochemistry 2024, 10(11), 90; https://doi.org/10.3390/magnetochemistry10110090 - 18 Nov 2024

Abstract

In recent decades, the chemistry of transition metal coordination compounds has undergone continuous development at both scientific and application levels. The diversity of metal(II) complexes, along with their structural features and physicochemical properties, makes them attractive for a wide range of applications. The [...] Read more.

In recent decades, the chemistry of transition metal coordination compounds has undergone continuous development at both scientific and application levels. The diversity of metal(II) complexes, along with their structural features and physicochemical properties, makes them attractive for a wide range of applications. The dicyanamide ion (N(CN)₂) has the ability to form various transition metal compounds characterized by different architectures and topologies. The interaction of π-electrons from the nitrile groups with the π-system of the central nitrogen may enable electron delocalization, potentially facilitating electron transfer between the metal centers through the bridging dicyanamide (dca) ligand. This review focuses on dca–Co(II) compounds and, after a brief introduction, the structural aspects and magnetic properties are analyzed in detail. Full article

(This article belongs to the Special Issue Magnetic Coordination Compounds and More... a Long and Successful Story: A Tribute to M. Julve and F. Lloret)

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12 pages, 1800 KiB

Open AccessArticle

A Bifurcated Reconnecting Current Sheet in the Turbulent Magnetosheath

by Shimou Wang, Rongsheng Wang, Kai Huang and Jin Guo

Magnetochemistry 2024, 10(11), 89; https://doi.org/10.3390/magnetochemistry10110089 - 11 Nov 2024

Abstract

We report the Magnetospheric Multiscale (MMS) observation of a bifurcated reconnecting current sheet in Earth’s dayside magnetosheath. Typical signatures of the ion diffusion region, including sub-Alfvénic demagnetized ion outflow, super-Alfvénic electron flows, Hall magnetic fields, electron heating, and energy dissipation, were found when [...] Read more.

We report the Magnetospheric Multiscale (MMS) observation of a bifurcated reconnecting current sheet in Earth’s dayside magnetosheath. Typical signatures of the ion diffusion region, including sub-Alfvénic demagnetized ion outflow, super-Alfvénic electron flows, Hall magnetic fields, electron heating, and energy dissipation, were found when MMS traversed the current sheet. The weak ion exhaust at the current sheet center was bounded by two current peaks in which super-Alfvénic electron flow directed toward and away from the X line were observed, respectively. Both off-center current peaks were primarily carried by electrons, one of which was supported by field-aligned current, while the other was mainly supported by current driven by electric field drift. The two current peaks also exhibit other differences, including electron heating, electron pitch angle distributions, electron nongyrotropy, energy dissipation, and magnetic field curvature. An ion-scale magnetic flux rope was detected between the two current peaks where electrons showed field-aligned bidirectional distribution, in contrast to field-aligned distribution parallel to the magnetic field in two current peaks. The observed current sheet was embedded in a background shear flow. This shear flow worked together with the guide field and asymmetric field and density to affect the electron dynamics. Our results reveal the reconnection properties in this special plasma and field regime which may be common in turbulent environments. Full article

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

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15 pages, 3616 KiB

Open AccessArticle

Polarizing Magnetic Field Effect on Some Electrical Properties of a Ferrofluid in Microwave Field

by Catalin N. Marin, Paul C. Fannin and Iosif Malaescu

Magnetochemistry 2024, 10(11), 88; https://doi.org/10.3390/magnetochemistry10110088 - 9 Nov 2024

Abstract

The complex dielectric permittivity, ε (f, H) = ε′ (f, H) − i ε″ (f, H), in the microwave frequency range f, of (0.1–3) GHz and polarizing field values H, [...] Read more.

The complex dielectric permittivity, ε (f, H) = ε′ (f, H) − i ε″ (f, H), in the microwave frequency range f, of (0.1–3) GHz and polarizing field values H, in the range of (0–135) kA/m, was measured for a kerosene-based ferrofluid with magnetite particles. A relaxation process attributed to interfacial type relaxation was highlighted, determining for the first time in the microwave field, the activation energy of the dielectric relaxation process in the presence of the magnetic field, E_A(H), in relation to the activation energy in zero field, E_A(H = 0). Based on the complex permittivity measurements and the Claussius–Mossotti equation, the dependencies on frequency (f), and magnetic field (H), of the polarizability (α) and electrical conductivity (σ), were determined. From the dependence of α(f,H), the electric dipolar moment, p, of the particles in the ferrofluid, was determined. The conductivity spectrum, σ(f,H), was found to be in agreement with Jonscher’s universal law and the electrical conduction mechanism in the ferrofluid was explained using both Mott’s VRH (variable range hopping) model and CBH (correlated barrier hopping) model. Based on these models and conductivity measurements, the hopping distance, R_h, of the charge carriers and the maximum barrier height, W_m, for the investigated ferrofluid was determined for the first time in the microwave field. Knowledge of these electrical properties of the ferrofluid in the microwave field is useful for explaining the mechanisms of polarization and control of electrical conductivity with an external magnetic field, in order to use ferrofluids in various technological applications in microwave field. Full article

(This article belongs to the Special Issue Ferrofluids - Electromagnetic Properties and Applications)

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24 pages, 10317 KiB

Open AccessArticle

Magnetic CuFe₂O₄ Nanoparticles Immobilized on Modified Rice Husk-Derived Zeolite for Chlorogenic Acid Adsorption

by Tainara Ramos Neves, Letícia Ferreira Lacerda Schildt, Maria Luiza Lopes Sierra e Silva, Vannyla Viktória Viana Vasconcelos, Corrado Di Conzo, Francesco Mura, Marco Rossi, Gaspare Varvaro, Maryam Abdolrahimi, Simone Quaranta, Sandra Aparecida Duarte Ferreira and Elaine Cristina Paris

Magnetochemistry 2024, 10(11), 87; https://doi.org/10.3390/magnetochemistry10110087 - 4 Nov 2024

Abstract

Adsorption has emerged as a promising method for removing polyphenols in water remediation. This work explores chlorogenic acid (CGA) adsorption on zeolite-based magnetic nanocomposites synthesized from rice husk waste. In particular, enhanced adsorbing materials were attained using a hydrothermal zeolite precursor (Z18) synthesized [...] Read more.

Adsorption has emerged as a promising method for removing polyphenols in water remediation. This work explores chlorogenic acid (CGA) adsorption on zeolite-based magnetic nanocomposites synthesized from rice husk waste. In particular, enhanced adsorbing materials were attained using a hydrothermal zeolite precursor (Z18) synthesized from rice husk and possessing a remarkable specific surface area (217.69 m² g⁻¹). A composite material was prepared by immobilizing magnetic copper ferrite on Z18 (Z18:CuFe₂O₄) to recover the zeolite adsorbent. In addition, Z18 was modified (Z18 M) with a mixture of 3-aminopropyltriethoxysilane (APTES) and trimethylchlorosilane (TMCS) to improve the affinity towards organic compounds in the final nanocomposite system (Z18 M:CuFe₂O₄). While the unmodified composite demonstrated inconsequential CGA removal rates, Z18 M:CuFe₂O₄ could adsorb 89.35% of CGA within the first hour of operation. Z18 M:CuFe₂O₄ showed no toxicity for seed germination and achieved a mass recovery of 85% (due to a saturation magnetization of 4.1 emu g⁻¹) when an external magnetic field was applied. These results suggest that adsorbing magnetic nanocomposites are amenable to CGA polyphenol removal from wastewater. Furthermore, the reuse, revalorization, and conversion into value-added materials of agro-industrial waste may allow the opportunity to implement sustainability and work towards a circular economy. Full article

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

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12 pages, 2875 KiB

Open AccessArticle

Two New 2p–3d Metal Complexes with a Nitronyl-Nitroxide Ligand Derived from o-Vanillin: Synthesis, Crystals Structures and Magnetic Properties

by Cristian Andrei Spinu, Daniel O. T. A. Martins, Teodora Mocanu, Mihaela Hillebrand, Jean-Pascal Sutter, Floriana Tuna and Marius Andruh

Magnetochemistry 2024, 10(11), 86; https://doi.org/10.3390/magnetochemistry10110086 - 1 Nov 2024

Abstract

Two new 2p–3d complexes, (Et₃NH)[ML(hfac)₂], have been obtained using the nitronyl-nitroxide radical (HL) derived from 2-hydroxy-3-methoxy-5-nitrobenzaldehyde (M = Mn 1; Co 2). The two compounds are isomorphous and their structures consist of anionic mononuclear species, [M(hfac)₂ [...] Read more.

Two new 2p–3d complexes, (Et₃NH)[ML(hfac)₂], have been obtained using the nitronyl-nitroxide radical (HL) derived from 2-hydroxy-3-methoxy-5-nitrobenzaldehyde (M = Mn 1; Co 2). The two compounds are isomorphous and their structures consist of anionic mononuclear species, [M(hfac)₂L]⁻, M = Mn 1; Co 2, and triethylammonium cations, Et₃NH⁺. The metal ions adopt an octahedral geometry, being coordinated by phenoxido and aminoxyl oxygen atoms from the ligand and four oxygen atoms from the hexafluoroacetylacetonato (hfac⁻) ligand. The cryomagnetic behaviors of the two compounds reveal relatively strong antiferromagnetic M(II)-Rad interactions (J_MnRad = −191 cm⁻¹, J_CoRad = −166 cm⁻¹ with H = −JS_MS_Rad). The EPR spectra (X- and Q-band) of compound 1 below 70 K show the characteristical features of a S = 2 spin system with zero field splitting terms of D = 0.26 cm⁻¹ and E = 0.031 cm⁻¹. Full article

(This article belongs to the Special Issue Magnetic Coordination Compounds and More... a Long and Successful Story: A Tribute to M. Julve and F. Lloret)

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13 pages, 4372 KiB

Open AccessArticle

Slow Magnetic Relaxation in a [Co₄O₄] Cubane Complex with Tridentate NNO-Schiff Base Ligands

by Yuki Suemitsu, Yoshitaka Amakusa, Haruka Yoshino, Masaaki Ohba and Masayuki Koikawa

Magnetochemistry 2024, 10(11), 85; https://doi.org/10.3390/magnetochemistry10110085 - 30 Oct 2024

Abstract

Two tetranuclear Co(II) complexes, [Co₄(pmab)₄Cl₄] (1) and [Co₄(pmab)₄(OBz)₂]Cl₂ (2) [Hpmab = 2-{(p-pyridinylmethylene)amino}benzenemethanol], have been synthesized and characterized through single-crystal X-ray diffraction, IR and UV-VIS [...] Read more.

Two tetranuclear Co(II) complexes, [Co₄(pmab)₄Cl₄] (1) and [Co₄(pmab)₄(OBz)₂]Cl₂ (2) [Hpmab = 2-{(p-pyridinylmethylene)amino}benzenemethanol], have been synthesized and characterized through single-crystal X-ray diffraction, IR and UV-VIS spectroscopy, and magnetic measurements. Structural analysis revealed that both complexes possess a [Co₄O₄] cubane-like metal core connected by μ₃-alkoxo bridges. Magnetic measurements of Complex 1 indicate weak ferromagnetic interactions (J ~ +0.75 cm⁻¹) within the tetranuclear core, while Complex 2 exhibits antiferromagnetic behavior due to the presence of syn-syn bridging benzoate ligands. Alternating current (AC) magnetic measurements suggest that Complex 1 exhibits slow magnetic relaxation behavior. Full article

(This article belongs to the Section Molecular Magnetism)

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11 pages, 2385 KiB

Open AccessArticle

Radiation-Induced Paramagnetic Centers in Meso- and Macroporous Synthetic Opals from EPR and ENDOR Data

by Alexander Rodionov, Larisa Latypova, Georgy Mamin and Marat Gafurov

Magnetochemistry 2024, 10(11), 84; https://doi.org/10.3390/magnetochemistry10110084 - 30 Oct 2024

Abstract

The paramagnetic defects and radiation-induced paramagnetic centers (PCs) in silica opals can play a crucial role in determining the magnetic and electronic behavior of materials and serve as local probes of their electronic structure. Systematic investigations of paramagnetic defects are essential for advancing [...] Read more.

The paramagnetic defects and radiation-induced paramagnetic centers (PCs) in silica opals can play a crucial role in determining the magnetic and electronic behavior of materials and serve as local probes of their electronic structure. Systematic investigations of paramagnetic defects are essential for advancing both theoretical and practical aspects of material science. A series of silica opal samples with different geometrical parameters were synthesized and radiation-induced PCs were investigated by means of the conventional and pulsed X- and W-band electron paramagnetic resonance, and ¹H/²H Mims electron-nuclear double resonance. Two groups of PCs were distinguished based on their spectroscopic parameters, electron relaxation characteristics, temperature and time stability, localization relative to the surface of silica spheres, and their origin. The obtained data demonstrate that stable radiation-induced E’ PCs can be used as sensitive probes for the hydrogen-containing fillers of the opal pores, for the development of compact radiation monitoring equipment, and for quantum technologies. Full article

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23 pages, 4716 KiB

Open AccessReview

Influence of Magnetic Field on Calcium Carbonate Precipitation: A Critical Review

by Fathi Alimi

Magnetochemistry 2024, 10(11), 83; https://doi.org/10.3390/magnetochemistry10110083 - 29 Oct 2024

Abstract

This review reports a critical study on the effect of magnetic fields on the precipitation process of calcium carbonate scale from hard water. Indeed, the harmful consequences of the water scaling phenomenon urged researchers to find effective solutions. One of the interesting antiscaling [...] Read more.

This review reports a critical study on the effect of magnetic fields on the precipitation process of calcium carbonate scale from hard water. Indeed, the harmful consequences of the water scaling phenomenon urged researchers to find effective solutions. One of the interesting antiscaling processes is the magnetic treatment of water, which triggers a reduction in the precipitation of calcium carbonate on the walls when in contact with hard water. In the present review, we discuss selected examples related to this process in a combined analysis of the latest advances and the mechanism of action of the magnetic field. Despite the diversity of studies investigating this phenomenon, the effectiveness of this treatment remains a controversial issue, and it is not possible to obtain a clear explanation of the phenomenon. This review proposes, finally, interesting hypotheses which can effectively explain the effect of magnetic treatment on the behavior of hard waters and the precipitation of calcium carbonate, which include magnetohydrodynamics and the hydration effect. Full article

(This article belongs to the Section Magnetic Field)

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16 pages, 6467 KiB

Open AccessArticle

Strong Antiferromagnetic Interactions in the Binuclear Cobalt(II) Complex with a Bridged Nitroxide Diradical

by Vitaly A. Morozov, Eugenia V. Peresypkina, Wolfgang Wernsdorfer and Kira E. Vostrikova

Magnetochemistry 2024, 10(11), 82; https://doi.org/10.3390/magnetochemistry10110082 - 28 Oct 2024

Abstract

A binuclear cobalt–radical complex formed by the reaction of Co(hfac)₂·2H₂O (hfac = hexafluoroacetylacetonate) with the 2,2-bis(1-oxyl-3-oxide-4,4,5,5-tetramethylimidazolinyl) biradical (BR) has been synthesized. The complex {(hfac)Co^II(BN)Co^II(hfac)} crystallizes in the triclinic space group P

\bar{1}

: C [...] Read more.

A binuclear cobalt–radical complex formed by the reaction of Co(hfac)₂·2H₂O (hfac = hexafluoroacetylacetonate) with the 2,2-bis(1-oxyl-3-oxide-4,4,5,5-tetramethylimidazolinyl) biradical (BR) has been synthesized. The complex {(hfac)Co^II(BN)Co^II(hfac)} crystallizes in the triclinic space group P

\bar{1}

: C₃₄H₂₈Co₂F₂₄N₄O₁₂, a = 11.1513(5) Å, b = 12.8362(7) Å, c = 18.2903(8) Å, α = 103.061(1)°, β = 100.898(2)°, γ = 102.250(1)°, Z = 2. The compound consists of two non-equivalent pseudo-octahedral Co^II ions, each bearing two hfac ancillary ligands bridged by the tetradentate bis-nitroxide (BN). The temperature dependence of the magnetic susceptibility indicates a strong antiferromagnetic exchange between each of the Co²⁺ ions and the nitroxyl biradical, as well as between the spins within the bridging ligand, forming a spin-frustrated system. Micro-squid investigations, performed on a single crystal of {(hfac)Co^II(BN)Co^II(hfac)}, reveal a peculiarity of the M(H) graph at temperatures below 0.4 K displaying a step that is a result of ground and first excited levels mixing by the applied magnetic field due to a small energy gap between them, as inferred from ab initio calculation. The latter was also carried out for two models of mononuclear Co²⁺ complexes in order to obtain a set of initial parameters for fitting the experimental magnetic curves using the Phi program. Moreover, direct CAS(12,10)/def2-TZVP calculations of the magnetic dependences χT(T) and M(H) were performed, which satisfactorily reproduced the experimental ones. Full article

(This article belongs to the Section Molecular Magnetism)

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16 pages, 7713 KiB

Open AccessArticle

Digital Magnetic Sorting for Fractionating Cell Populations with Variable Antigen Expression in Cell Therapy Process Development

by Savannah Bshara-Corson, Andrew Burwell, Timothy Tiemann and Coleman Murray

Magnetochemistry 2024, 10(11), 81; https://doi.org/10.3390/magnetochemistry10110081 - 23 Oct 2024

Abstract

Cellular therapies exhibit immense potential in treating complex diseases with sustained responses. The manufacture of cell therapies involves the purification and engineering of specific cells from a donor or patient to achieve a therapeutic response upon injection. Magnetic cell sorting targeting the presence [...] Read more.

Cellular therapies exhibit immense potential in treating complex diseases with sustained responses. The manufacture of cell therapies involves the purification and engineering of specific cells from a donor or patient to achieve a therapeutic response upon injection. Magnetic cell sorting targeting the presence or absence of surface markers is commonly used for upfront purification. However, emerging research shows that optimal therapeutic phenotypes are characterized not only by the presence or absence of specific antigens but also by antigen density. Unfortunately, current cell purification tools like magnetic or fluorescence-activated cell sorting (FACS) lack the resolution to differentiate populations based on antigen density while maintaining scalability. Utilizing a technique known as digital magnetic sorting (DMS), we demonstrate proof of concept for a scalable, magnetic-based approach to fractionate cell populations based on antigen density level. Targeting CD4 on human leukocytes, DMS demonstrated fractionation into CD4^Hi T cells and CD4^Low monocytes and neutrophils as quantified by flow cytometry and single-cell RNA seq. DMS also demonstrated high throughput processing at throughputs 3–10× faster than FACS. We believe DMS can be leveraged and scaled to enable antigen density-based sorting in cell therapy manufacturing, leading to the production of more potent and sustainable cellular therapies. Full article

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

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14 pages, 1486 KiB

Open AccessArticle

Analysis of Magnetization Dynamics in NiFe Thin Films with Growth-Induced Magnetic Anisotropies

by Leah Merryweather and Aidan T. Hindmarch

Magnetochemistry 2024, 10(10), 80; https://doi.org/10.3390/magnetochemistry10100080 - 21 Oct 2024

Abstract

We have used angled magnetron sputter deposition with and without sample rotation to control the magnetic anisotropy in 20 nm NiFe films. Ferromagnetic resonance spectroscopy, with data analysis using a Bayesian approach, is used to extract material parameters relating to the magnetic anisotropy. [...] Read more.

We have used angled magnetron sputter deposition with and without sample rotation to control the magnetic anisotropy in 20 nm NiFe films. Ferromagnetic resonance spectroscopy, with data analysis using a Bayesian approach, is used to extract material parameters relating to the magnetic anisotropy. When the sample is rotated during growth, only shape anisotropy is present, but when the sample is held fixed, a strong uniaxial anisotropy emerges with in-plane easy axis along the azimuthal direction of the incident atom flux. When the film is deposited in two steps, with an in-plane rotation of 90 degrees between steps, the two orthogonal induced in-plane easy-axes effectively cancel. The analysis approach enables precise and accurate determination of material parameters from ferromagnetic resonance measurements; this demonstrates the ability to precisely control both the direction and strength of uniaxial magnetic anisotropy, which is important in magnetic thin-film device applications. Full article

(This article belongs to the Special Issue Fabrication, Characterization and Application of Magnetic Thin Films)

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15 pages, 3871 KiB

Open AccessArticle

Comprehensive Characterization of Bi_1.34Fe_0.66Nb_1.34O_6.35 Ceramics: Structural, Morphological, Electrical, and Magnetic Properties

by Susana Devesa, Carlos Oliveira Amorim, João Horta Belo, João P. Araújo, Sílvia Soreto Teixeira, Manuel P. F. Graça and Luís Cadillon Costa

Magnetochemistry 2024, 10(10), 79; https://doi.org/10.3390/magnetochemistry10100079 - 20 Oct 2024

Abstract

Recent research in solid-state physics and materials engineering focuses on the development of new dielectric materials, with bismuth-based pyrochlores being already extensively applied in communications technology for their excellent dielectric properties and relatively low sintering temperatures. Herein, the structural, morphological, electrical, and magnetic [...] Read more.

Recent research in solid-state physics and materials engineering focuses on the development of new dielectric materials, with bismuth-based pyrochlores being already extensively applied in communications technology for their excellent dielectric properties and relatively low sintering temperatures. Herein, the structural, morphological, electrical, and magnetic properties of Bi_1.34Fe_0.66Nb_1.34O_6.35 ceramic, prepared by the sol–gel method and sintered at 500 °C, are investigated. The Rietveld refinement of the XRD pattern showed a cubic phase belonging to the space group Fd-3m and a crystallite size of 42 nm. Transmission electron microscopy further confirmed the crystallite size and the homogeneous distribution of Bi, Fe, Nb, and O elements, as evidenced by high-angle annular dark field imaging and STEM-EDX mapping. The morphology of the sample, assessed by scanning electron microscopy, is characterized by submicron-sized spherical particles. Dielectric spectroscopic studies revealed that the dielectric properties, strongly influenced by frequency and temperature, indicate the material’s potential for energy storage due to lower dielectric loss compared to the dielectric constant. The observed relaxation phenomena, confirmed through variations in dielectric loss and loss tangent, highlight the influence of grain boundaries and temperature on electron hopping and charge carrier dynamics. Using SQUID magnetometry, we identified two distinct magnetic phases. The primary phase, corresponding to the Bi_1.34Fe_0.66Nb_1.34O_6.35 ceramic, exhibits an antiferromagnetic behavior below its Néel temperature at around 8.8 K. A secondary high-Curie temperature ferrimagnetic phase, likely vestigial maghemite and/or magnetite, was also detected, indicating an estimated fraction below 0.02 wt.%. Full article

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14 pages, 1485 KiB

Open AccessArticle

Short-Period Skyrmion Crystals in Itinerant Body-Centered Tetragonal Magnets

by Satoru Hayami

Magnetochemistry 2024, 10(10), 78; https://doi.org/10.3390/magnetochemistry10100078 - 16 Oct 2024

Abstract

In this study, we investigate the stability of a magnetic skyrmion crystal with short-period magnetic modulations in a centrosymmetric body-centered tetragonal system. By performing the simulated annealing for the spin model, incorporating the effects of the biquadratic interaction and high-harmonic wave–vector interaction in [...] Read more.

In this study, we investigate the stability of a magnetic skyrmion crystal with short-period magnetic modulations in a centrosymmetric body-centered tetragonal system. By performing the simulated annealing for the spin model, incorporating the effects of the biquadratic interaction and high-harmonic wave–vector interaction in momentum space, we find that the double-Q square skyrmion crystal consisting of two spin density waves is stabilized in an external magnetic field. We also show that double-Q states appear in both low- and high-field regions; the low-field spin configuration is characterized by an anisotropic double-Q modulation consisting of a superposition of the spiral wave and sinusoidal wave, while the high-field spin configuration is characterized by an isotropic double-Q modulation consisting of a superposition of two sinusoidal waves. Furthermore, we show that the obtained multiple-Q instabilities can be realized for various ordering wave vectors. The results provide the possibility of realizing the short-period skyrmion crystals under the body-centered tetragonal lattice structure. Full article

(This article belongs to the Special Issue Spin and Charge Transport in Novel Quantum and Topological Materials)

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17 pages, 8054 KiB

Open AccessArticle

Incorporation of Superparamagnetic Magnetic–Fluorescent Iron Oxide Nanoparticles Increases Proliferation of Human Mesenchymal Stem Cells

by Willian Pinheiro Becker, Juliana Barbosa Torreão Dáu, Wanderson de Souza, Rosalia Mendez-Otero, Rosana Bizon Vieira Carias and Jasmin

Magnetochemistry 2024, 10(10), 77; https://doi.org/10.3390/magnetochemistry10100077 - 12 Oct 2024

Abstract

Mesenchymal stem cells (MSCs) have significant therapeutic potential and their use requires in-depth studies to better understand their effects. Labeling cells with superparamagnetic iron oxide nanoparticles allows real-time monitoring of their location, migration, and fate post-transplantation. This study aimed to investigate the efficacy [...] Read more.

Mesenchymal stem cells (MSCs) have significant therapeutic potential and their use requires in-depth studies to better understand their effects. Labeling cells with superparamagnetic iron oxide nanoparticles allows real-time monitoring of their location, migration, and fate post-transplantation. This study aimed to investigate the efficacy and cytotoxicity of magnetic–fluorescent nanoparticles in human adipose tissue-derived mesenchymal stem cells (hADSCs). The efficacy of Molday ION rhodamine B (MIRB) labeling in hADSCs was evaluated and their biocompatibility was assessed using various techniques and differentiation assays. Prussian blue and fluorescence staining confirmed that 100% of the cells were labeled with MIRB and this labeling persisted for at least 3 days. Transmission electron microscopy revealed the internalization and clustering of the nanoparticles on the outer surface of the cell membrane. The viability assay showed increased cell viability 3 days after nanoparticle exposure. Cell counts were higher in the MIRB-treated group compared to the control group at 3 and 5 days and an increased cell proliferation rate was observed at 3 days post-exposure. Adipogenic, osteogenic, and chondrogenic differentiation was successfully achieved in all groups, with MIRB-treated cells showing an enhanced differentiation rate into adipocytes and osteocytes. MIRB was efficiently internalized by hADSCs but induced changes in cellular behavior due to the increased cell proliferation rate. Full article

(This article belongs to the Special Issue Advances in Magnetic Nanoparticles: Biocompatibility, Toxicity, and Biomedical Applications)

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13 pages, 2979 KiB

Open AccessArticle

[Mn^III₆Mn^IINa^I₂], [Mn^III₃Mn^IINa^I], and [Mn^III₃] Clusters Derived from Schiff Bases: Syntheses, Structures, and Magnetic Properties

by Johannes Löhr, Mercè Font-Bardia, Júlia Mayans and Albert Escuer

Magnetochemistry 2024, 10(10), 76; https://doi.org/10.3390/magnetochemistry10100076 - 10 Oct 2024

Abstract

The reaction of manganese halides with polydentate Schiff bases obtained by the condensation of 3-ethoxysalicylaldehyde and different amino alcohols, resulting in a NO₃ set of donors, yielded a series of manganese clusters with {Mn^III₆Mn^IINa₂}, {Mn [...] Read more.

The reaction of manganese halides with polydentate Schiff bases obtained by the condensation of 3-ethoxysalicylaldehyde and different amino alcohols, resulting in a NO₃ set of donors, yielded a series of manganese clusters with {Mn^III₆Mn^IINa₂}, {Mn^III₃Mn^IINa}, and {Mn^III₃} metallic cores. The influence of the ligand substituents and the halide on the final nuclearity has been studied. Analysis of their static magnetic behaviour confirms the ground states of 19/2 for the {Mn^III₆Mn^IINa₂} complexes, 7/2 for the {Mn^III₃Mn^IINa} clusters, and 12/2 for the triangular {Mn^III₃} systems, and a weak field induced a slow relaxation of the magnetization for the trinuclear complexes. Full article

(This article belongs to the Special Issue Magnetic Coordination Compounds and More... a Long and Successful Story: A Tribute to M. Julve and F. Lloret)

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17 pages, 3275 KiB

Open AccessArticle

Optimizing Magnetic Separation and Cleaning Module in Fully Automated Chemiluminescence Immunoassay Analyzer Using a Special Arrangement of Spliced Magnets and a Three-Stage Magnetic Bead Collection Method

by Chuan Lyu, Yu Jiang, Zhen Dai, Xu Xu, Yu Cai, Bo Liang, Congcong Zhou, Xuesong Ye and Jing Wang

Magnetochemistry 2024, 10(10), 75; https://doi.org/10.3390/magnetochemistry10100075 - 30 Sep 2024

Abstract

The magnetic separation and cleaning module, as a core component of the fully automated chemiluminescence immunoassay (CLIA) analyzer, encounters issues including high magnetic bead loss rate, long cleaning time, and poor cleaning effect. Based on a simulation analysis using COMSOL, we proposed a [...] Read more.

The magnetic separation and cleaning module, as a core component of the fully automated chemiluminescence immunoassay (CLIA) analyzer, encounters issues including high magnetic bead loss rate, long cleaning time, and poor cleaning effect. Based on a simulation analysis using COMSOL, we proposed a novel magnetic separation and cleaning module applied to a fully automated CLIA analyzer. The module adopted a method of arranging spliced rectangular magnets on opposite sides, where the same polarity faced each other, as well as a three-stage magnetic bead collection method. With the proposed method, the total cleaning process can be accomplished within 225 s; the total magnetic bead loss rate over three rounds of cleaning is 6.03%, whereas that of traditional instruments is 25.85%; the coefficient of variation (CV) of the magnetic bead loss rate is less than 0.5%; effective cleaning of free markers is achieved under various sample conditions. Compared with traditional CLIA instruments, this method comprehensively improves key performance indicators of the magnetic separation and cleaning module, providing a reference for similar modules in fully automated CLIA analyzers and positively impacting the accuracy of CLIA for the detection of disease biomarkers. Full article

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

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14 pages, 2923 KiB

Open AccessArticle

Facile Synthesis of Core-Shell Magnetic Iron Oxide@SiO₂-NH₂ Nanoparticles and Their Application in Rapid Boron Removal from Aqueous Solutions

by Qinqin Hu, Manman Zhang, Jiaoyu Peng, Yaping Dong, Wu Li and Lingzong Meng

Magnetochemistry 2024, 10(10), 74; https://doi.org/10.3390/magnetochemistry10100074 - 30 Sep 2024

Abstract

In this study, amino-functionalized magnetic particles (iron oxide@SiO₂-NH₂) with core-shell structures were synthesized and evaluated for rapid boron removal from aqueous solutions. The results showed that the specific surface area of the iron oxide@SiO₂-NH₂ (131.24 m [...] Read more.

In this study, amino-functionalized magnetic particles (iron oxide@SiO₂-NH₂) with core-shell structures were synthesized and evaluated for rapid boron removal from aqueous solutions. The results showed that the specific surface area of the iron oxide@SiO₂-NH₂ (131.24 m²⋅g⁻¹) increased greatly compared to pure iron oxide (30.98 m²⋅g⁻¹). The adsorption equilibrium was less than 2 h, with an adsorption capacity of 29.76 mg⋅g⁻¹ at pH = 6 at 15 °C. The quasi-second-order kinetic model described the boron adsorption process well, and both the Langmuir and Freundlich models were suitable for characterizing the adsorption isotherms. The zeta potential and XPS analysis before and after adsorption revealed that the main adsorption mechanism was the hydrogen bonding formation between the terminal -NH₂ groups of the adsorbent and the boric acid. In addition, the adsorbent still maintained a high adsorption performance after five adsorption–desorption cycles, which illustrated that the iron oxide@SiO₂-NH₂ may be a potential adsorbent for environmental boron removal treatment. Full article

(This article belongs to the Special Issue Current Trends in Magnetic Metallic Materials and Nanocomposites)

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