Magnetochemistry

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

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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7 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

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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45 pages, 5094 KiB

Open AccessArticle

The Origin of Homochirality by Rotational Magnetoelectrochemistry

by Ryoichi Morimoto, Iwao Mogi, Miki Miura, Atsushi Sugiyama, Makoto Miura, Yoshinobu Oshikiri, Kohki Takahashi, Yusuke Yamauchi and Ryoichi Aogaki

Magnetochemistry 2025, 11(6), 51; https://doi.org/10.3390/magnetochemistry11060051 - 19 Jun 2025

Abstract

The origin of homochirality by rotational magnetoelectrochemistry was theoretically examined. Electrochemical reductions in a rotating solution under a static vertical magnetic field were concluded to yield microscopic vortices with L-activity for enantiomeric reagents, whereas D-active vortices arise from electrochemical oxidation. The reduction case [...] Read more.

The origin of homochirality by rotational magnetoelectrochemistry was theoretically examined. Electrochemical reductions in a rotating solution under a static vertical magnetic field were concluded to yield microscopic vortices with L-activity for enantiomeric reagents, whereas D-active vortices arise from electrochemical oxidation. The reduction case was experimentally verified by rotational magnetoelectrodeposition (RMED) of copper films using an electrolysis cell rotating in a magnetic field, where L-active screw dislocations were created by L-active microscopic vortices. In all the cases of the directions of magnetic polarity and system rotation, the RMED films exhibited L-activity for the enantiomeric reactions of amino acids. Full article

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18 pages, 3833 KiB

Open AccessArticle

Reverse Curve Fitting Approach for Quantitative Deconvolution of Closely Overlapping Triplets in Fourier Transform Nuclear Magnetic Resonance Spectroscopy Using Odd-Order Derivatives

by Shu-Ping Chen, Sandra M. Taylor, Sai Huang and Baoling Zheng

Magnetochemistry 2025, 11(6), 50; https://doi.org/10.3390/magnetochemistry11060050 - 17 Jun 2025

Abstract

A new deconvolution strategy, reverse curve fitting, was developed to determine peak positions and independent intensities of overlapping Fourier transform (FT) nuclear magnetic resonance (NMR) bands. From the third-order derivative of the overlapping band, the peak position was estimated from its zero-crossing point [...] Read more.

A new deconvolution strategy, reverse curve fitting, was developed to determine peak positions and independent intensities of overlapping Fourier transform (FT) nuclear magnetic resonance (NMR) bands. From the third-order derivative of the overlapping band, the peak position was estimated from its zero-crossing point and the peak intensity was quantitated by partial curve matching with its primary maxima. Every matched peak in the overlapping band was dismembered in turn to weaken the overlap until an independent peak was filtered out. The deconvolution can be refined progressively by manually tuning the peak positions and peak widths. In a simulation study, a closely overlapped ¹³C NMR triplet (overlapping degrees between 0.5 and 1.0) at a signal-to-noise ratio (SNR) of 20:1 was quantitatively deconvoluted by our reverse curve fitting procedure with a routine denoising technique. The noise interference and denoising technique were also studied in the simulation. A real FT-NMR overlapping band of Ethylbenzene (300 MHz) was satisfactorily deconvoluted and compatible with higher resolution literature spectral data. A more complicated overlapping NMR band of Tetraphenyl porphyrin was studied as well. This new approach to the deconvolutions is applicable to other FT spectroscopies. Full article

(This article belongs to the Section Magnetic Resonances)

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20 pages, 5439 KiB

Open AccessArticle

The Efficient Degradation of Oxytetracycline in Wastewater Using Fe/Mn-Modified Magnetic Oak Biochar: Pathways and Mechanistic Investigation

by Yujie Zhou, Yuzhe Fu, Xiaoxue Niu, Bohan Wu, Xinghan Liu, Fu Hao, Zichuan Ma, Hao Cai and Yuheng Liu

Magnetochemistry 2025, 11(6), 49; https://doi.org/10.3390/magnetochemistry11060049 - 6 Jun 2025

Abstract

Antibiotic resistance has been recognized as a global threat to human health. Therefore, it is urgent to develop effective strategies to address the contamination of water environments caused by antibiotics. In this study, Fe/Mn bimetallic-modified biochar (FMBC) was synthesized through a one-pot oxidation/reduction-hydrothermal [...] Read more.

Antibiotic resistance has been recognized as a global threat to human health. Therefore, it is urgent to develop effective strategies to address the contamination of water environments caused by antibiotics. In this study, Fe/Mn bimetallic-modified biochar (FMBC) was synthesized through a one-pot oxidation/reduction-hydrothermal co-precipitation method, demonstrating an exceptional photocatalytic-Fenton degradation performance for oxytetracycline (OTC). Characterization techniques including FTIR, SEM, XRD, VSM, and N₂ adsorption–desorption analysis confirmed that the Fe/Mn bimetals were successfully loaded onto the surface of biochar in the form of Fe₃O₄ and MnFe₂O₄ mixed crystals and exhibited favorable paramagnetic properties that facilitate magnetic recovery. A key innovation is the utilization of biochar’s inherent phenol/quinone structures as reactive sites and electron transfer mediators, which synergistically interact with the loaded bimetallic oxides to significantly enhance the generation of highly reactive ·OH radicals, thereby boosting catalytic activity. Even after five recycling cycles, the material exhibited minimal changes in degradation efficiency and bimetallic crystal structure, indicating its notable stability and reusability. The photocatalytic degradation experiment conducted in a Fenton-like reaction system demonstrates that, under the conditions of pH 4.0, a H₂O₂ concentration of 5.16 mmol/L, a catalyst dosage of 0.20 g/L, and an OTC concentration of 100 mg/L, the optimal degradation efficiency of 98.3% can be achieved. Additionally, the pseudo-first-order kinetic rate constant was determined to be 4.88 min⁻¹. Furthermore, this study elucidated the detailed degradation mechanisms, pathways, and the influence of various ions, providing valuable theoretical insights and technical support for the degradation of antibiotics in real wastewater. Full article

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

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13 pages, 1841 KiB

Open AccessArticle

A Heptacobalt(II/III) Dicubane Cluster with Polyoxometalate and Acetato Ligands: Synthesis, Crystal Structure, and Magnetic Properties

by Gonzalo Abellán-Dumont, Juan Modesto Clemente-Juan and Carlos Giménez-Saiz

Magnetochemistry 2025, 11(6), 48; https://doi.org/10.3390/magnetochemistry11060048 - 3 Jun 2025

Cited by 1

Abstract

The new polyoxometalate [Co₇(OH)₆(H₂O)₂(CH₃COO)₄(PW₉O₃₄)₂]¹³⁻ (1) has been synthesized and characterized by IR, UV-Vis-NIR, TGA-TDA, X-ray single crystal analysis, and magnetic studies; 1 [...] Read more.

The new polyoxometalate [Co₇(OH)₆(H₂O)₂(CH₃COO)₄(PW₉O₃₄)₂]¹³⁻ (1) has been synthesized and characterized by IR, UV-Vis-NIR, TGA-TDA, X-ray single crystal analysis, and magnetic studies; 1 consists of two trilacunary heptadentate B-α-[PW₉O₃₄]⁹⁻ ligands encapsulating a heptacobalt dicubane-like {Co^II₆Co^IIIO₈} core, in which the Co²⁺ ions are further coordinated by two water molecules and four acetate anions acting as monodentate ligands. The magnetic properties of 1 have been fitted according to an anisotropic exchange model in the low-temperature regime and discussed on the basis of ferromagnetic interactions between Co²⁺ ions with angles Co–L–Co (L = O, OH) close to orthogonality and weakly antiferromagnetic interactions between Co²⁺ ions connected through a central diamagnetic Co³⁺ ion. 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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Graphical abstract

18 pages, 2149 KiB

Open AccessReview

Nuclear Magnetic Resonance-Based Approaches for the Structural and Quantitative Analysis of Mycotoxins

by Yun Hwan Kim, Seon Yeong Lee, Jin Young Kim, Hyojin Cho, Hyang Sook Chun and Sangdoo Ahn

Magnetochemistry 2025, 11(6), 47; https://doi.org/10.3390/magnetochemistry11060047 - 3 Jun 2025

Abstract

Mycotoxins are toxic secondary metabolites produced by various fungal species, posing significant food safety concerns due to their health impacts and economic burden. Accurate structural elucidation and quantitative analysis are essential for effective risk assessment and regulatory control. This review highlights recent advances [...] Read more.

Mycotoxins are toxic secondary metabolites produced by various fungal species, posing significant food safety concerns due to their health impacts and economic burden. Accurate structural elucidation and quantitative analysis are essential for effective risk assessment and regulatory control. This review highlights recent advances in the application of nuclear magnetic resonance (NMR) spectroscopy for the structural and quantitative analysis of major mycotoxins, including aflatoxins, ochratoxins, fumonisins, trichothecenes, and zearalenone. One- and two-dimensional NMR techniques enable precise molecular characterization, positional isomer identification, including modified forms such as masked or conjugated mycotoxins, and toxicity-related molecular interaction investigation. NMR spectroscopy offers superior structural resolution, high reproducibility, and nondestructive analysis, making it invaluable in mycotoxin research. Quantitative NMR spectroscopy has emerged as a robust and accurate method for determining the absolute concentration and purity of mycotoxins, without requiring analyte-specific reference standards, an advantage particularly important for modified toxins lacking commercially available standards. The integration of NMR-based approaches strengthens analytical reliability, supports reference material development, and contributes to enhanced food safety assessment. This review also discusses ongoing analytical challenges and future directions, including the application of artificial intelligence to improve the automation and interpretation of NMR data in mycotoxin research. Full article

(This article belongs to the Section Magnetic Resonances)

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18 pages, 5082 KiB

Open AccessArticle

Research on 3D Magnetic Memory Signals Induced by Circular Hole Defects

by Bin Yang, Zhifeng Liu and Yang Gao

Magnetochemistry 2025, 11(6), 46; https://doi.org/10.3390/magnetochemistry11060046 - 25 May 2025

Abstract

Metal magnetic memory testing technology can not only detect macroscopic defects in ferromagnetic materials but also rapidly and conveniently detect early damage and stress concentration areas of components. Therefore, it is widely used in the nondestructive testing of ferromagnetic materials. However, the mechanism [...] Read more.

Metal magnetic memory testing technology can not only detect macroscopic defects in ferromagnetic materials but also rapidly and conveniently detect early damage and stress concentration areas of components. Therefore, it is widely used in the nondestructive testing of ferromagnetic materials. However, the mechanism of magnetic memory detection is not yet clarified, and experimental research is unsystematic. Previous studies mainly focus on the normal and tangential components of magnetic memory signals (MMSs), and the third directional component is rarely considered, resulting in problems such as missed detection and misjudgement in practical applications. In this research, specimens without and with a circular hole defect were designed, and the correlation between the 3D MMS and the defect size, as well as the applied load, were investigated using tensile tests. Magnetic parameters were defined to characterize the stress and defect-induced abnormal magnetic change. The effects of applied load and defect size on magnetic parameters were discussed. The experimental results showed that the peak–valley difference in the 3D MMS increases with increasing load and defect size, and the peak–valley spacing in the 3D MMS is not influenced by applied load but increases with increasing defect size. The 3D MMS gradient exhibits a good correlation with the equivalent stress along the loading direction. Additionally, the applied load and defect size were quantitatively evaluated by utilizing the Lissajous figure area generated from the X and Z components of the 3D MMS. Finally, a nonlinear fitting equation for defect size evaluation was presented. This study can provide a theoretical basis for the quantitative detection and evaluation of defect size and stress in engineering applications. Full article

(This article belongs to the Special Issue Latest Updates in Soft Magnetic Materials)

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7 pages, 1778 KiB

Open AccessArticle

Synthesis, Structure and Magnetic Properties of Sm_6−xLa_xMn₂₃ (0.5 ≤ x ≤ 4) Alloys

by Ying-Hua Liang, Zhong Zhang, Jihoon Park, Jia-Cheng Lyu, Hong-Liang Ge, Ping-Zhan Si and Chul-Jin Choi

Magnetochemistry 2025, 11(5), 45; https://doi.org/10.3390/magnetochemistry11050045 - 21 May 2025

Abstract

The structure and magnetic properties of Sm_6−xLa_xMn₂₃ (x = 0.5, 1, 2, 3 and 4) alloys have been studied systematically. We found that the Th₆Mn₂₃-type Sm_6−xLa_xMn₂₃ [...] Read more.

The structure and magnetic properties of Sm_6−xLa_xMn₂₃ (x = 0.5, 1, 2, 3 and 4) alloys have been studied systematically. We found that the Th₆Mn₂₃-type Sm_6−xLa_xMn₂₃ alloys become less stable with increasing La content, and α-Mn becomes the dominant phase at x = 4. More impurities were found to present in Sm₅LaMn₂₃ samples prepared by a rapid solidification process than those present in the as-cast ingots. The coercivity of Sm₄La₂Mn₂₃ induction-melted ingots and Sm₅LaMn₂₃ melt-spun ribbons reached up to 0.47 T and 0.53 T, respectively, indicating potential applications of this alloy in hard magnetic materials. The Curie temperature of Sm_6−xLa_xMn₂₃ falls in the range of 398 K for x = 1 to 438 K for x = 3. The La-substitution results in a reduced saturation magnetization of Sm_6−xLa_xMn₂₃, owing to a reduced total-magnetic-moment contribution of the Sm-sublattices. This work provides us a deeper understanding of the effect of La-substitution on the structure and magnetic properties of the ternary La-Sm-Mn alloys. Full article

(This article belongs to the Section Magnetic Materials)

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17 pages, 6448 KiB

Open AccessArticle

Development of NiZn Ferrites Doped with Co for Low Power Losses at High Frequencies (10 MHz) and High Temperatures (>80 °C)

by Stefanos Zaspalis, Georgios Kogias, Vassilios Zaspalis, Eustathios Kikkinides, Elisabeth Rauchenwald, Christoph Vogler and Kevin Ouda

Magnetochemistry 2025, 11(5), 44; https://doi.org/10.3390/magnetochemistry11050044 - 17 May 2025

Abstract

Polycrystalline nickel–zinc (NiZn) ferrites are widely used in high-frequency applications due to their excellent magnetic properties such as low power losses, high magnetic permeability, and adequate saturation induction. However, data on their power loss behavior at 10 MHz, particularly at elevated temperatures, remain [...] Read more.

Polycrystalline nickel–zinc (NiZn) ferrites are widely used in high-frequency applications due to their excellent magnetic properties such as low power losses, high magnetic permeability, and adequate saturation induction. However, data on their power loss behavior at 10 MHz, particularly at elevated temperatures, remain limited in the literature. This study investigates the magnetic performance of Co-doped NiZn ferrites at 10 MHz, under varying induction fields (3–10 mT) and temperatures (20–120 °C), with a focus on reducing high-temperature losses. Ferrite samples were synthesized using the conventional mixed oxide method and systematically varied in composition (Fe, Co content and Ni/Zn molar ratio). Key findings reveal that the incorporation of cobalt significantly enhances high-temperature performance by shifting resonance frequencies, attributed to increased domain wall pinning. Samples with optimized compositions and processing demonstrated power losses at 10 MHz, 10 mT and 25 °C, 100 °C and 120 °C as low as 310 mW cm⁻³, 1233 mW cm⁻³ and 1400 mW cm⁻³, respectively, with relative initial permeabilities exceeding 80 at these temperatures. These results provide insights into the design of high-frequency magnetic components and highlight strategies to minimize high-temperature losses. Full article

(This article belongs to the Special Issue Design and Applications of Advanced Magnetic Ceramic Materials: New Insights)

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9 pages, 1128 KiB

Open AccessArticle

ESR and Mössbauer Spectroscopy of Iron(III) Spin Crossover Complexes Based on Pentadentate Schiff Base Ligands with Pseudohalide Coligands

by Rene Lucka, Besnik Elshani, Maximilian Seydi Kilic, Stephen Klimke, Christoph Krüger, Michael Menzel, Reinhard Stößer, Ján Titiš, Roman Boča and Franz Renz

Magnetochemistry 2025, 11(5), 43; https://doi.org/10.3390/magnetochemistry11050043 - 10 May 2025

Abstract

Two iron(III) spin crossover complexes [Fe(⁵Cl-L)(NCS)] (1) and [Fe(⁵Cl-L)(NCSe)] (2) were synthesized with the pentadentate Schiff base ligand ⁵Cl-L and thiocyanato and selenocyanato as coligands. ⁵Cl-L, as an asymmetric {N₃O₂ [...] Read more.

Two iron(III) spin crossover complexes [Fe(⁵Cl-L)(NCS)] (1) and [Fe(⁵Cl-L)(NCSe)] (2) were synthesized with the pentadentate Schiff base ligand ⁵Cl-L and thiocyanato and selenocyanato as coligands. ⁵Cl-L, as an asymmetric {N₃O₂} donor Schiff base, was synthesized by a condensation reaction of 5-chlorosalicyladehyde using the asymmetric N-(2-aminoethyl)-1,3-propanediamine. The complexes exhibited a spin crossover at 280 (1) and 293 K (2), respectively, and were subjected to electron spin resonance (ESR) and Mössbauer spectroscopy at 77, 295 and 325 K. Ab initio CASSCF calculations followed by the NEVPT2 method were applied for predicting the g-tensor components as well as Mössbauer parameters. Full article

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

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13 pages, 364 KiB

Open AccessArticle

The Magnetic Properties and Band-Gap Energy of CuFeO₂—Bulk Materials and Nanoparticles—Doped with Mn, Sc, Mg at the Fe Site, and Li, Ca at the Cu Site

by Angel T. Apostolov, Iliana N. Apostolova and Julia M. Wesselinowa

Magnetochemistry 2025, 11(5), 42; https://doi.org/10.3390/magnetochemistry11050042 - 10 May 2025

Abstract

We have investigated for the first time the temperature, size, and ion-doping concentration dependence of the magnetic properties, band-gap energy, and specific heat of CuFeO₂ in both bulk materials and nanoparticles using a microscopic model (the s-d model) and Green’s function theory. [...] Read more.

We have investigated for the first time the temperature, size, and ion-doping concentration dependence of the magnetic properties, band-gap energy, and specific heat of CuFeO₂ in both bulk materials and nanoparticles using a microscopic model (the s-d model) and Green’s function theory. Variations in the ionic radii of the dopant elements compared to those of the host ions introduce strain effects, which alter the exchange-interaction constants. Consequently, the influence of ion doping on the various properties of CuFeO₂ nanoparticles has been elucidated at a microscopic level. The magnetization exhibits an increase when CuFeO₂ is doped with Mn at the Fe site or Li and Ca at the Cu site, whereas doping with Sc or Mg at the Fe site leads to a decrease in magnetization. Regarding the band-gap energy, it increases upon doping with Mg and Sc at the Fe site, while doping with Mn at the Fe site or with Li and Ca at the Cu site results in a decrease. The temperature dependence of the specific heat reveals two distinct peaks, corresponding to the two magnetic phase-transition temperatures. The theoretical results show good qualitative agreement with experimental data, confirming the validity of the proposed model. Full article

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9 pages, 1986 KiB

Open AccessArticle

Multifunctional Synergistic Response Induced by Phase Transition in Molecular Compounds

by Xiao-Feng Chen, Tao Wang, Dan Liao, Nan Wu, Yan Peng, Shi-Yong Zhang and Zhao-Bo Hu

Magnetochemistry 2025, 11(5), 41; https://doi.org/10.3390/magnetochemistry11050041 - 9 May 2025

Abstract

Two organic–inorganic materials (TMAA)₂[CoCl₄] (1) and (TMAA)₂[MnCl₄] (2) (TMAA = N,N,N-trimethyl-1-adamantylammonium hydroxide) were synthesized and characterized. It was found that both compounds exhibit first-order structural phase transition at high-temperature regions. As [...] Read more.

Two organic–inorganic materials (TMAA)₂[CoCl₄] (1) and (TMAA)₂[MnCl₄] (2) (TMAA = N,N,N-trimethyl-1-adamantylammonium hydroxide) were synthesized and characterized. It was found that both compounds exhibit first-order structural phase transition at high-temperature regions. As the temperature approaches the phase transition point, significant abnormal changes were observed in the dielectric properties and χ_MT values of compounds 1 and 2. This phenomenon strongly highlights the dielectric bistable and spin bistable properties of compounds 1 and 2. Further research shows that the dielectric constants of the compounds undergo significant changes upon the application of an external magnetic field, providing strong evidence for the existence of magnetic–dielectric coupling effects within compounds 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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30 pages, 5545 KiB

Open AccessArticle

Design of Ricker Wavelet Neural Networks for Heat and Mass Transport in Magnetohydrodynamic Williamson Nanofluid Boundary-Layer Porous Medium Flow with Multiple Slips

by Zeeshan Ikram Butt, Muhammad Asif Zahoor Raja, Iftikhar Ahmad, Muhammad Shoaib, Rajesh Kumar and Syed Ibrar Hussain

Magnetochemistry 2025, 11(5), 40; https://doi.org/10.3390/magnetochemistry11050040 - 9 May 2025

Abstract

In the current paper, an analysis of magnetohydrodynamic Williamson nanofluid boundary layer flow is presented, with multiple slips in a porous medium, using a newly designed human-brain-inspired Ricker wavelet neural network solver. The solver employs a hybrid approach that combines genetic algorithms, serving [...] Read more.

In the current paper, an analysis of magnetohydrodynamic Williamson nanofluid boundary layer flow is presented, with multiple slips in a porous medium, using a newly designed human-brain-inspired Ricker wavelet neural network solver. The solver employs a hybrid approach that combines genetic algorithms, serving as a global search method, with sequential quadratic programming, which functions as a local optimization technique. The heat and mass transportation effects are examined through a stretchable surface with radiation, thermal, and velocity slip effects. The primary flow equations, originally expressed as partial differential equations (PDEs), are changed into a dimensionless nonlinear system of ordinary differential equations (ODEs) via similarity transformations. These ODEs are then numerically solved with the proposed computational approach. The current study has significant applications in a variety of practical engineering and industrial scenarios, including thermal energy systems, biomedical cooling devices, and enhanced oil recovery techniques, where the control and optimization of heat and mass transport in complex fluid environments are essential. The numerical outcomes gathered through the designed scheme are compared with reference results acquired through Adam’s numerical method in terms of graphs and tables of absolute errors. The rapid convergence, effectiveness, and stability of the suggested solver are analyzed using various statistical and performance operators. Full article

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9 pages, 1598 KiB

Open AccessArticle

Rhenium-Induced Negative Magnetoresistance in Monolayer Graphene

by Ying Zhang, Jiali You, Weiwei Li, Zijie Huang, Yuxiang Feng, Yuyu Liu and Jing Li

Magnetochemistry 2025, 11(5), 39; https://doi.org/10.3390/magnetochemistry11050039 - 6 May 2025

Abstract

The impact of rhenium doping on the transport properties and electron localization in monolayer graphene was experimentally investigated. In this study, we report the emergence of unsaturated negative magnetoresistance in Re-doped graphene devices, which is observed exclusively at low temperatures. Moreover, angle-dependent measurements [...] Read more.

The impact of rhenium doping on the transport properties and electron localization in monolayer graphene was experimentally investigated. In this study, we report the emergence of unsaturated negative magnetoresistance in Re-doped graphene devices, which is observed exclusively at low temperatures. Moreover, angle-dependent measurements reveal a pronounced anisotropy in the negative magnetoresistance. This phenomenon is attributed to the disorder and localized magnetic moments introduced by Re doping, which lead to charge carrier localization and are accompanied by substantial magnetocrystalline anisotropy energy. Full article

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13 pages, 4778 KiB

Open AccessArticle

Synthesis, X-Ray Crystal Structures, and Magnetic Properties of a Series of Trinuclear Rare-Earth Hepta-Chloride Clusters

by Yingying Pan, You-Song Ding, Lei Li and Zhiping Zheng

Magnetochemistry 2025, 11(5), 38; https://doi.org/10.3390/magnetochemistry11050038 - 2 May 2025

Abstract

Organometallic rare-earth complexes have attracted considerable attention in recent years due to their unique structures and exceptional magnetic properties. In this study, we report the synthesis and magnetic characteristics of a family of monopentamethylcyclopentadienyl-coordinated trinuclear rare-earth hepta-chloride clusters [(Li(THF)(Et₂O))(Cp^*RE) [...] Read more.

Organometallic rare-earth complexes have attracted considerable attention in recent years due to their unique structures and exceptional magnetic properties. In this study, we report the synthesis and magnetic characteristics of a family of monopentamethylcyclopentadienyl-coordinated trinuclear rare-earth hepta-chloride clusters [(Li(THF)(Et₂O))(Cp^*RE)₃(μ-Cl)₄(μ₃-Cl)₂(μ₄-Cl)] (RE₃: RE =Y, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu; Cp* = pentamethylcyclopentadienide). These clusters were synthesized by reacting LiCp* with RECl₃ in a 1:1 molar ratio within a mixed solvent system (THF: Et₂O = 1:9), resulting in high solubility in common organic solvents such as DCM, THF, and Et₂O. Magnetic studies conducted on these paramagnetic clusters reveal the coexistence of ferromagnetic and antiferromagnetic superexchange interactions in Gd₃. Additionally, Dy₃ exhibits both ferromagnetic and antiferromagnetic intramolecular dipolar interactions. Notably, slow magnetic relaxation was observed in Dy₃ below 23 K under a zero DC applied field with an energy barrier of 125(6) cm⁻¹. 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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16 pages, 7645 KiB

Open AccessArticle

Case Study on Homogeneous–Heterogeneous Chemical Reactions in a Magneto Hydrodynamics Darcy–Forchheimer Model with Bioconvection in Inclined Channels

by Subhan Ullah, Walid Emam, Zeeshan Ali, Dolat Khan, Dragan Pamucar and Zareen A. Khan

Magnetochemistry 2025, 11(5), 37; https://doi.org/10.3390/magnetochemistry11050037 - 2 May 2025

Cited by 1

Abstract

This study focuses on understanding the bioconvection in Jeffery–Hamel (JH) flow, which has valuable applications in areas like converging dies, hydrology, and the automotive industry, which make it a topic of practical importance. This research aims to explore Homogeneous–Heterogeneous (HH) chemical reactions in [...] Read more.

This study focuses on understanding the bioconvection in Jeffery–Hamel (JH) flow, which has valuable applications in areas like converging dies, hydrology, and the automotive industry, which make it a topic of practical importance. This research aims to explore Homogeneous–Heterogeneous (HH) chemical reactions in a magnetic Darcy–Forchheimer model with bioconvection in convergent/divergent channels. To analyze the role of porosity, the Darcy–Forchheimer law is applied. The main system of equations is simplified through similarity transformation into ordinary differential equations solved numerically with the help of the NDSolve technique. The results, compared with previous studies for validation, are presented through graphs and tables. The study reveals that in divergent channels, the velocity decreases with higher solid volume fractions, while in convergent channels, it increases. Furthermore, various physical parameters, such as the Eckert number and porosity parameter, increase skin friction in divergent channels but decrease it in convergent channels. These findings suggest that the parameters investigated in this study can effectively enhance homogeneous reactions, providing valuable insights for practical applications. Full article

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12 pages, 4964 KiB

Open AccessArticle

Cationic Mismatch Effect Induced by Double Substitution on the Structural and Magnetic Properties of La_0.5Ca_0.5MnO₃

by Wadie Abdelhedi, Akram Krichene, Wahiba Boujelben and Nassira Chniba-Boudjada

Magnetochemistry 2025, 11(5), 36; https://doi.org/10.3390/magnetochemistry11050036 - 23 Apr 2025

Abstract

In this study, we aimed to induce controlled structural disorder through a double substitution approach in the La_0.5Ca_0.5MnO₃ compound by investigating La_0.5−xRe_xCa_0.5−yAe_yMnO₃ compounds with x = 0.05 [...] Read more.

In this study, we aimed to induce controlled structural disorder through a double substitution approach in the La_0.5Ca_0.5MnO₃ compound by investigating La_0.5−xRe_xCa_0.5−yAe_yMnO₃ compounds with x = 0.05 and 0.1 and Re = Eu, Nd, Gd, Pr, and Ae = Ba and Sr. The y values are adjusted to maintain a constant average ionic radius (<r_A> = 1.198 Å) and an unchanged Mn^3+/Mn⁴⁺ ratio. These samples were synthesized using the sol–gel method. XRD analysis confirms structural stability despite the induced disorder, showing subtle lattice distortions. Magnetic measurements reveal that introducing low disorder annihilates the charge ordered (CO) state, enhances double-exchange interactions, and influences the ferromagnetic (FM) volume fractions. Moderate disorder strengthens AFM–CO state, triggering a first–order metamagnetic transition and reducing the Curie temperature value. Magnetic field-dependent magnetization data show disorder dependent magnetic behavior and suggest the presence of the Griffiths phase for all samples, confirming the role of structural disorder in tuning magnetic phase coexistence. Pr-based samples display a considerable magnetocaloric effect near their Curie temperature. Full article

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

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24 pages, 6174 KiB

Open AccessArticle

Copper(II)-Promoted Reactions of α-Pyridoin Oxime: A Dodecanuclear Cluster and a 2D Coordination Polymer

by Konstantina H. Baka, Luís Cunha-Silva, Catherine P. Raptopoulou, Vassilis Psycharis, Dionissios Papaioannou, Mark M. Turnbull, Zoi G. Lada, Spyros P. Perlepes and Theocharis C. Stamatatos

Magnetochemistry 2025, 11(4), 35; https://doi.org/10.3390/magnetochemistry11040035 - 18 Apr 2025

Abstract

The reaction of CuCl₂∙2H₂O, (E)-2-hydroxy-1,2-di(pyridin-2-yl)ethanone oxime (α-pyroxH₂) and Et₃N in refluxing MeOH gave complex [Cu₁₂Cl₁₂(mpydol)₄(pydox)₂(MeOH)₄] (1), where mpydol²⁻ is the [...] Read more.

The reaction of CuCl₂∙2H₂O, (E)-2-hydroxy-1,2-di(pyridin-2-yl)ethanone oxime (α-pyroxH₂) and Et₃N in refluxing MeOH gave complex [Cu₁₂Cl₁₂(mpydol)₄(pydox)₂(MeOH)₄] (1), where mpydol²⁻ is the dianion of 1,2-dimethoxy-1,2-di(pyridin-2-yl)ethane-1,2-diol and pydox²⁻ is the dianion of (E,E)-1,2-di(pyridin-2-yl)ethanedione dioxime. “Blind” experiments have proven that the transformation of α-pyroxH₂ is copper(II)-assisted. By changing the solvent from MeOH to MeCN, the polymeric compound {[Cu₄Cl₄(pic)₄]}_n (2) was isolated; pic⁻ is the pyridine-2-carboxylato(-1) ligand. The observed α-pyroxH₂ → pic⁻ transformation is also copper(II)-assisted. The topology of the metal ions in 1 can be described as consisting of four consecutive isosceles triangles in a zigzag configuration. Complex 2 is a 2D coordination polymer consisting of Cu^II₄ squares. Complete mechanistic views for the α-pyroxH₂ → mpydol²⁻, pydox²⁻ and pic⁻ transformations are critically discussed. In 1, the six Cu^II ions of the “central” triangles seem to be strongly antiferromagnetically coupled, thus cancelling out their spins (

S_{{Cu}_{6}}

= 0). The two local spins of S = 1/2 for each of the antiferromagnetically coupled “terminal” Cu^II₃ triangles result in an overall S = 1 ground state spin value for 1. In 2, the four Cu^II ions within each tetrameric unit are practically isolated and ferromagnetic interactions occur between these units through Cu^II–(μ-Cl)–Cu^II bridges. Full article

(This article belongs to the Special Issue Latest Research on the Magnetic Properties of Coordination Compounds)

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