Magnetochemistry

9 pages, 679 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 (registering DOI) - 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)

13 pages, 354 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 (registering DOI) - 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 CuFeO

_{2}

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 CuFeO

_{2}

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 CuFeO

_{2}

nanoparticles has been elucidated at a microscopic level. The magnetization exhibits an increase when CuFeO

_{2}

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

9 pages, 930 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

Viewed by 78

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)

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

Viewed by 70

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

Viewed by 124

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

Viewed by 256

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

Viewed by 215

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

Viewed by 176

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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Magnetochemistry, Volume 11, Issue 5 (May 2025) – 8 articles

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