Magnetochemistry

25 pages, 2780 KiB

Open AccessArticle

Motion of Magnetic Microcapsules Through Capillaries in the Presence of a Magnetic Field: From a Mathematical Model to an In Vivo Experiment

by Mikhail N. Zharkov, Mikhail A. Pyataev, Denis E. Yakobson, Valentin P. Ageev, Oleg A. Kulikov, Vasilisa I. Shlyapkina, Dmitry N. Khmelenin, Larisa A. Balykova, Gleb B. Sukhorukov and Nikolay A. Pyataev

Magnetochemistry 2025, 11(7), 60; https://doi.org/10.3390/magnetochemistry11070060 - 14 Jul 2025

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Abstract

In this paper, we discuss the prediction of the delivery efficiency of magnetic carriers based on their properties and field parameters. We developed a theory describing the behavior of magnetic capsules in the capillaries of living systems. A partial differential equation for the [...] Read more.

In this paper, we discuss the prediction of the delivery efficiency of magnetic carriers based on their properties and field parameters. We developed a theory describing the behavior of magnetic capsules in the capillaries of living systems. A partial differential equation for the spatial distribution of magnetic capsules has been obtained. We propose to characterize the interaction between the magnetic field and the capsules using a single vector, which we call “specific magnetic force”. To test our theory, we performed experiments on a model of a capillary bed and on a living organism with two types of magnetic capsules that differ in size and amount of magnetic material. The experimental results show that the distribution of the capsules in the field correlated with the theory, but there were fewer actually accumulated capsules than predicted by the theory. In the weaker fields, the difference was more significant than in stronger ones. We proposed an explanation for this phenomenon based on the assumption that a certain level of magnetic force is needed to keep the capsules close to the capillary wall. We also suggested a formula for the relationship between the probability of capsule precipitation and the magnetic force. We found the effective value of a specific magnetic force at which all the capsules attracted by the magnet reach the capillary wall. This value can be considered as the minimum level for the field at which it is, in principle, possible to achieve a significant magnetic control effect. We demonstrated that for each type of capsule, there is a specific radius of magnet for which the effective magnetic force is achieved at the largest possible distance from the magnet’s surface. For the capsules examined in this study, the maximum distance where the effective field can be achieved does not exceed 1.5 cm. The results of the study contribute to our understanding of the behavior of magnetic particles in the capillaries of living organisms when exposed to a magnetic field. Full article

(This article belongs to the Special Issue Fundamentals and Applications of Novel Functional Magnetic Materials)

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25 pages, 5298 KiB

Open AccessArticle

Microstructural, Mechanical, Thermal, and Magnetic Properties of the Mechanically Alloyed and Consolidated Al–16 wt. % Mn–7 wt. % Cu Alloy

by Ahlem Saad Bekhouche, Safia Alleg, Abdelaziz Bouasla, Hacene Hachache and Joan José Sunol

Magnetochemistry 2025, 11(7), 59; https://doi.org/10.3390/magnetochemistry11070059 - 11 Jul 2025

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Abstract

The effect of severe plastic deformation during milling and conventional and Spark Plasma Sintering (SPS) on the wt. % microstructural, structural, thermal, magnetic, and mechanical properties of the Al–16 wt. % Mn–7 wt. % Cu alloy was studied. A milling process for up [...] Read more.

The effect of severe plastic deformation during milling and conventional and Spark Plasma Sintering (SPS) on the wt. % microstructural, structural, thermal, magnetic, and mechanical properties of the Al–16 wt. % Mn–7 wt. % Cu alloy was studied. A milling process for up to 24 h (A24) leads to microstructure refinement and the presence of Al, Mn, and Cu solid solutions. The energy dispersive spectroscopy (EDS) analysis reveals the existence of Cu–Al, Mn–Al, and Al–Mn enriched particles. The powders exhibit weak ferromagnetism and an exchange bias (EB) behaviour that decreases with increasing milling time. The Ms values fitted using the law of approach to saturation (LAS) are comparable to the experimental values. The exothermic and endothermic peaks that appear in the differential scanning calorimetry (DSC) scans in the 500–900 °C range on heating/cooling are related to different phase transformations. The crystal structure of the A24 powders heated up to 900 °C (A24_900 °C) consists of a dual-phase microstructure of Al₂₀Cu₂Mn₃ nanoprecipitates (~28%) and Al matrix (~72%). The sintering of the A24 powders at 500 °C for one hour (A24S) leads to the precipitation of Al₆Mn, Al₂Cu, and the Al₂₀Cu₂Mn₃ T-phase into the Al-enriched matrix. In contrast, the consolidation by SPS (A24SPS) leads to a mixture of an Al solid solution, Al₆Mn, T-phase, and α-Mn with an increased weight fraction of the T-phase and Al₆Mn. The sintered samples exhibit the coexistence of a significant PM/AFM contribution to the M-H curves, with increasing Hc and decreasing EB. A higher microhardness value of about 581 HV is achieved for the A24SPS sample compared to those of the A24 (68 HV) and A24S (80 HV) samples. Full article

(This article belongs to the Special Issue Structure, Magnetic and Thermal Properties of Nanocrystalline Materials)

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13 pages, 2394 KiB

Open AccessArticle

Two Dy₂ Zero-Field Single-Molecule Magnets Derived from Hydrazone Schiff Base-Bridging Ligands and 1,3-Di(2-pyridyl)-1,3-propanedione

by Cai-Ming Liu

Magnetochemistry 2025, 11(7), 58; https://doi.org/10.3390/magnetochemistry11070058 - 2 Jul 2025

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Abstract

Two hydrazone Schiff base-bridging ligands with different heterocycles {2-[(E)-(5-chloro-2-hydroxyphenyl)methylidene]diazanyl}(pyrazine-2-yl)methanone (H₂L_Schiff-1) and (E)-N′-(2-hydroxy-3-methoxybenzylidene)nicotinohydrazide (H₂L_Schiff-2) together with 1,3-di(2-pyridyl)-1,3-propanedione (Hdpp) were chosen to construct two new Dy₂ complexes, [Dy₂(L [...] Read more.

Two hydrazone Schiff base-bridging ligands with different heterocycles {2-[(E)-(5-chloro-2-hydroxyphenyl)methylidene]diazanyl}(pyrazine-2-yl)methanone (H₂L_Schiff-1) and (E)-N′-(2-hydroxy-3-methoxybenzylidene)nicotinohydrazide (H₂L_Schiff-2) together with 1,3-di(2-pyridyl)-1,3-propanedione (Hdpp) were chosen to construct two new Dy₂ complexes, [Dy₂(L_Schiff-1)₂(DMF)₂(dpp)₂]·0.5DMF (1) and [Dy₂(L_Schiff-2)₂(DMF)₂(dpp)₂]·2DMF (2). Although the [N₂O₆] coordination spheres are observed for the Dy³⁺ ions in 1 and 2, their coordination configurations have some differences (both the biaugmented trigonal prism and the Snub diphenoid J84 in 1 and only the biaugmented trigonal prism in 2). Magnetic research revealed that both 1 and 2 possess ferromagnetic interactions between two Dy³⁺ ions and perform as zero-field single-molecule magnets, with U_eff/k values of 49.7 K at 0 Oe for 1 and 151.8 K at 0 Oe for 2. This work suggests that the heterocycle groups (pyrazine vs. pyridine) on the hydrazone Schiff base-bridging ligands have effects on the SMM properties of 1 and 2. Full article

(This article belongs to the Special Issue Molecular Magnetism: A Themed Issue in Honor of Professor Dai-Zheng Liao on the Occasion of His 85th Birthday)

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14 pages, 2951 KiB

Open AccessArticle

Magnetic Properties of an Ensemble of Core-Shell Fe/FeO_X Nanoparticles: Experimental Study and Micromagnetic Simulation

by Grigory Yu. Melnikov, Ekaterina A. Burban, Andrey V. Svalov and Galina V. Kurlyandskaya

Magnetochemistry 2025, 11(7), 57; https://doi.org/10.3390/magnetochemistry11070057 - 2 Jul 2025

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Abstract

Spherical magnetic nanoparticles consisting of an iron core and iron oxide shell (α-Fe/FeO_X) were fabricated by the electric explosion of the wire technique (EEW). The structure and magnetic properties of synthesized nanoparticles were experimentally investigated. Magnetic properties of an iron nanoparticle [...] Read more.

Spherical magnetic nanoparticles consisting of an iron core and iron oxide shell (α-Fe/FeO_X) were fabricated by the electric explosion of the wire technique (EEW). The structure and magnetic properties of synthesized nanoparticles were experimentally investigated. Magnetic properties of an iron nanoparticle ensemble for individual defect-free, non-interacting iron-based nanoparticles having different diameters were calculated using micromagnetic modeling. Experimental and calculated magnetic hysteresis loops were comparatively analyzed. Full article

(This article belongs to the Section Magnetic Materials)

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21 pages, 9209 KiB

Open AccessArticle

Effects of Exchange, Anisotropic, and External Field Couplings on a Nanoscale Spin-2 and Spin-3/2 System: A Thermomagnetic Analysis

by Julio Cesar Madera, Elisabeth Restrepo-Parra and Nicolás De La Espriella

Magnetochemistry 2025, 11(7), 56; https://doi.org/10.3390/magnetochemistry11070056 - 30 Jun 2025

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Abstract

In this research, an analysis of the thermomagnetic properties of a nanoscale spin-2 and spin-3/2 system is conducted. This system is modeled with as a quasi-spherical Ising-type nanoparticle with a diameter of 2 nm, in which atoms with spin-2 and spin-3/2 configured in [...] Read more.

In this research, an analysis of the thermomagnetic properties of a nanoscale spin-2 and spin-3/2 system is conducted. This system is modeled with as a quasi-spherical Ising-type nanoparticle with a diameter of 2 nm, in which atoms with spin-2 and spin-3/2 configured in body-centered cubic (BCC) lattices interact within their relevant nanostructures. To determine the thermomagnetic behaviors of the nanoparticle, numerical simulations using Monte Carlo techniques and thermal bath class algorithms are performed. The results exhibit the effects of exchange couplings (

J_{1}, J_{2}^{'}

), magnetocrystalline anisotropies (

D_{3 / 2}^{'}, D_{2}^{'}

), and external magnetic fields (

h^{'}

) on the finite-temperature phase diagrams of magnetization (

M_{T}

), magnetic susceptibility (

χ_{T}

), and thermal energy (

k_{B} T^{'}

). The influences of the exchange, anisotropic, and external field parameters are clearly reflected in the compensation, hysteretic, and pseudocritical phenomena presented by the quasi-spherical nanoparticle. When the parameter reflecting ferromagnetic second-neighbor exchanges in the nanosphere (

J_{2}^{'}

) increases, for a given value of the external magnetic field, the compensation (

T_{c o m p}

) and pseudocritical (

T_{p c}

) temperatures increase. Similarly, in the ranges

0 < J_{2}^{'} ⩽ 4.5

and

- 15 ⩽ h^{'} ⩽ 15

at a specific temperature, an increase in

J_{2}^{'}

results in the appearance of exchange anisotropies (exchange bias) and and increased hysteresis loop areas in the nanomodel. Full article

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14 pages, 17044 KiB

Open AccessArticle

Evolution of Griffiths-like Anomaly in Isostructural Swedenborgite Compounds Ho_1−xEr_xBaCo₄O_7+δ

by Biplab Pakhuria, Rafikul Ali Saha, Carlo Meneghini, Fabrice Bert, Shruti Kundu and Sugata Ray

Magnetochemistry 2025, 11(7), 55; https://doi.org/10.3390/magnetochemistry11070055 - 30 Jun 2025

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Abstract

In this study, we investigate the presence of the Griffiths-like anomaly in the geometrically frustrated antiferromagnet

{HoBaCo}_{4}

O_{7 + δ}

and globally its absence in

{ErBaCo}_{4}

O_{7 + δ}

, despite only small differences in the ionic radii, f [...] Read more.

In this study, we investigate the presence of the Griffiths-like anomaly in the geometrically frustrated antiferromagnet

{HoBaCo}_{4}

O_{7 + δ}

and globally its absence in

{ErBaCo}_{4}

O_{7 + δ}

, despite only small differences in the ionic radii, f-electron occupancy, and the corresponding crystal structures of the

{Ho}^{3 +}

and

{Er}^{3 +}

-members. Previous studies have identified the Griffiths phase in the Dy-analog,

{DyBaCo}_{4}

O_{7 + δ}

, suggesting certain inherent features of this class of materials that regularly give rise to such anomalies. To explore the curious disappearance of such an anomalous feature in

{ErBaCo}_{4}

O_{7 + δ}

, we prepared a series of compounds with varying compositions

{Ho}_{1 - x}

{Er}_{x}

{BaCo}_{4}

O_{7 + δ}

(

0 \leq x \leq 1

) and systematically studied the evolution of various physical properties as a function of Er-doping. Our experimental studies, including X-ray diffraction (XRD), magnetic, X-ray absorption spectroscopy (XAS), X-ray photoelectron spectroscopy (XPS), heat capacity, and muon spin relaxation spectroscopy (

μ

SR spectroscopy), revealed that while the Griffiths-like anomaly indeed disappears with doping at the macroscopic level, signatures of inhomogeneity are retained in

{ErBaCo}_{4}

O_{7 + δ}

too, at least at the local level. Overall, our results highlight the significant role of ionic radius and local structural distortions in stabilizing the Griffiths phase in this class of systems. Full article

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14 pages, 11764 KiB

Open AccessArticle

Excellent Microwave Absorption Properties in the C Band for the Nitrided Y₂Fe₁₂Co₄Si/Paraffin Composites

by Wenjian Tang, Hanxing Xu, Xichun Zhong, Na He, Zhongwu Liu and Raju V. Ramanujan

Magnetochemistry 2025, 11(7), 54; https://doi.org/10.3390/magnetochemistry11070054 - 24 Jun 2025

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Abstract

The nitriding process was employed to optimize the low-frequency microwave absorption properties of Y₂Fe₁₂Co₄Si/paraffin composites. The effects of nitriding temperature on the phase composition, static magnetic properties, electromagnetic parameters, and microwave absorption performance were systematically investigated. As [...] Read more.

The nitriding process was employed to optimize the low-frequency microwave absorption properties of Y₂Fe₁₂Co₄Si/paraffin composites. The effects of nitriding temperature on the phase composition, static magnetic properties, electromagnetic parameters, and microwave absorption performance were systematically investigated. As the nitriding temperature increases, lattice expansion results in a significant increase in saturation magnetization and a higher ratio of in-plane to out-of-plane anisotropy fields. This, in turn, boosts the electromagnetic parameters of the composite material. With a further rise in temperature, an increased content of α-Fe is produced and the ratio of the in-plane to out-of-plane anisotropy field diminishes, leading to a decline in electromagnetic parameters. At 500 °C, these factors reach an optimum level, maximizing the composite’s electromagnetic parameters. The composite exhibited a minimum reflection loss (RL_min) of −55.9 dB at 5.58 GHz with a thickness of 2.46 mm. Moreover, at a thickness of 2.21 mm, the composite achieved a maximum effective absorption bandwidth (EAB_max) of 2.95 GHz (5.05–8 GHz). Compared with other low-frequency-absorbing materials, the composite exhibited stronger absorption and a wider absorption bandwidth at a lower thickness in the C band. Full article

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14 pages, 5300 KiB

Open AccessArticle

Synthesis and Antibacterial Evaluation of Silver-Coated Magnetic Iron Oxide/Activated Carbon Nanoparticles Derived from Hibiscus esculentus

by Müslüm Güneş, Erdal Ertaş, Seyhmus Tumur, Parvin Zulfugarova, Fidan Nuriyeva, Taras Kavetskyy, Yuliia Kukhazh, Pavlo Grozdov, Ondrej Šauša, Oleh Smutok, Dashgin Ganbarov and Arnold Kiv

Magnetochemistry 2025, 11(7), 53; https://doi.org/10.3390/magnetochemistry11070053 - 21 Jun 2025

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Abstract

The increasing prevalence of antimicrobial resistance alongside the pharmacological limitations and adverse effects associated with conventional antibiotics necessitates the development of novel and efficacious antimicrobial agents. In this study, magnetic iron oxide nanoparticles (MIONPs) were synthesized via a chemical co-precipitation method. Activated carbon [...] Read more.

The increasing prevalence of antimicrobial resistance alongside the pharmacological limitations and adverse effects associated with conventional antibiotics necessitates the development of novel and efficacious antimicrobial agents. In this study, magnetic iron oxide nanoparticles (MIONPs) were synthesized via a chemical co-precipitation method. Activated carbon (AC) derived from Hibiscus esculentus (HE) fruit was coated onto the nanoparticle surfaces to fabricate MIONPs/HEAC nanocomposites. To augment their antimicrobial properties, silver ions were chemically reduced and deposited onto the MIONPs/HEAC surface, yielding MIONPs/HEAC@Ag nanocomposites. Comprehensive characterization of the synthesized nanocomposites was performed using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), vibrating sample magnetometry (VSM), dynamic light scattering (DLS), and zeta potential analysis. DLS measurements indicated average particle sizes of approximately 122 nm and 164 nm for MIONPs/HEAC and MIONPs/HEAC@Ag, respectively. Saturation magnetization values were determined to be 73.6 emu/g for MIONPs and 65.5 emu/g for MIONPs/HEAC. Antibacterial assays demonstrated that MIONPs/HEAC@Ag exhibited significant inhibitory effects against Escherichia coli ATCC 25922 and Staphylococcus aureus ATCC 25923, with inhibition zone diameters of 11.50 mm and 13.00 mm, respectively. In contrast, uncoated MIONPs/HEAC showed negligible antibacterial activity against both bacterial strains. These findings indicate that MIONPs/HEAC@Ag nanocomposites possess considerable potential as antimicrobial agents for biomedical applications, particularly in addressing infections caused by antibiotic-resistant bacteria. Full article

(This article belongs to the Special Issue Magnetic Nanoparticles and Nanocomposites for Bioanalytical and Biomedical Purposes)

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6 pages, 373 KiB

Open AccessEditorial

Magnetic Coordination Compounds and More… a Long and Successful Story: A Tribute to M. Julve and F. Lloret

by Carlos J. Gómez-García and Salah-Eddine Stiriba

Magnetochemistry 2025, 11(7), 52; https://doi.org/10.3390/magnetochemistry11070052 - 20 Jun 2025

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Abstract

This Special Issue of Magnetochemistry, entitled “Magnetic Coordination Compounds and More [...] 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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Magnetochemistry, Volume 11, Issue 7 (July 2025) – 9 articles

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