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Magnetochemistry
Volume 6
Issue 4
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Magnetochemistry, Volume 6, Issue 4 (December 2020) – 29 articles

Cover Story (view full-size image): The authors report on a long journey of molecular magnetism by Prof. Lloret’s research group covering almost 20 years of work on dicopper(II) metallacyclophanes and anticipating their performance as multifunctional and multiresponsive magnetic (nano)devices for future applications in the emerging fields of single-molecule spintronics and quantum computing. These metallosupramolecular complexes are prototypes of molecular magnetic wires and switches for the study of electron transport through and quantum-gated coherence in single molecules. The recent advances achieved in the metallosupramolecular chemistry approach toward molecular magnetism and future perspectives in nanoscience and nanotechnology are accounted from a proof-of-concept viewpoint. In so doing, our recent works and earlier ones on dicopper(II) metallacyclophanes are briefly discussed herein. View this paper
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22 pages, 5617 KiB  
Article
Novel Magnetic Nanohybrids: From Iron Oxide to Iron Carbide Nanoparticles Grown on Nanodiamonds
by Panagiotis Ziogas, Athanasios B. Bourlinos, Jiri Tucek, Ondrej Malina and Alexios P. Douvalis
Magnetochemistry 2020, 6(4), 73; https://doi.org/10.3390/magnetochemistry6040073 - 21 Dec 2020
Cited by 8 | Viewed by 3853
Abstract
The synthesis and characterization of a new line of magnetic hybrid nanostructured materials composed of spinel-type iron oxide to iron carbide nanoparticles grown on nanodiamond nanotemplates is reported in this study. The realization of these nanohybrid structures is achieved through thermal processing under [...] Read more.
The synthesis and characterization of a new line of magnetic hybrid nanostructured materials composed of spinel-type iron oxide to iron carbide nanoparticles grown on nanodiamond nanotemplates is reported in this study. The realization of these nanohybrid structures is achieved through thermal processing under vacuum at different annealing temperatures of a chemical precursor, in which very fine maghemite (γ-Fe2O3) nanoparticles seeds were developed on the surface of the nanodiamond nanotemplates. It is seen that low annealing temperatures induce the growth of the maghemite nanoparticle seeds to fine dispersed spinel-type non-stoichiometric ~5 nm magnetite (Fe3−xO4) nanoparticles, while intermediate annealing temperatures lead to the formation of single phase ~10 nm cementite (Fe3C) iron carbide nanoparticles. Higher annealing temperatures produce a mixture of larger Fe3C and Fe5C2 iron carbides, triggering simultaneously the growth of large-sized carbon nanotubes partially filled with these carbides. The magnetic features of the synthesized hybrid nanomaterials reveal the properties of their bearing magnetic phases, which span from superparamagnetic to soft and hard ferromagnetic and reflect the intrinsic magnetic properties of the containing phases, as well as their size and interconnection, dictated by the morphology and nature of the nanodiamond nanotemplates. These nanohybrids are proposed as potential candidates for important technological applications in nano-biomedicine and catalysis, while their synthetic route could be further tuned for development of new magnetic nanohybrid materials. Full article
(This article belongs to the Special Issue Recent Advances in Nanomagnetism)
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18 pages, 2966 KiB  
Review
Magnetic Nanoparticle-Based Drug Delivery Approaches for Preventing and Treating Biofilms in Cystic Fibrosis
by Marsha Tan, Felisa Reyes-Ortega and Elena K. Schneider-Futschik
Magnetochemistry 2020, 6(4), 72; https://doi.org/10.3390/magnetochemistry6040072 - 16 Dec 2020
Cited by 10 | Viewed by 4053
Abstract
Biofilm-associated infections pose a huge burden on healthcare systems worldwide, with recurrent lung infections occurring due to the persistence of biofilm bacteria populations. In cystic fibrosis (CF), thick viscous mucus acts not only as a physical barrier, but also serves as a nidus [...] Read more.
Biofilm-associated infections pose a huge burden on healthcare systems worldwide, with recurrent lung infections occurring due to the persistence of biofilm bacteria populations. In cystic fibrosis (CF), thick viscous mucus acts not only as a physical barrier, but also serves as a nidus for infection. Increased antibiotic resistance in the recent years indicates that current therapeutic strategies aimed at biofilm-associated infections are “failing”, emphasizing the need to develop new and improved drug delivery systems with higher efficacy and efficiency. Magnetic nanoparticles (MNPs) have unique and favourable properties encompassing biocompatibility, biodegradability, magnetic and heat-mediated characteristics, making them suitable drug carriers. Additionally, an external magnetic force can be applied to enhance drug delivery to target sites, acting as “nano-knives”, cutting through the bacterial biofilm layer and characteristically thick mucus in CF. In this review, we explore the multidisciplinary approach of using current and novel MNPs as vehicles of drug delivery. Although many of these offer exciting prospects for future biofilm therapeutics, there are also major challenges of this emerging field that need to be addressed. Full article
(This article belongs to the Special Issue Magnetic Nanoparticles 2020)
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51 pages, 10665 KiB  
Review
Lanthanoid-Anilato Complexes and Lattices
by Samia Benmansour and Carlos J. Gómez-García
Magnetochemistry 2020, 6(4), 71; https://doi.org/10.3390/magnetochemistry6040071 - 15 Dec 2020
Cited by 24 | Viewed by 3157
Abstract
In this review, we describe all the structurally characterized complexes containing lanthanoids (Ln, including La and group 3 metals: Y and Lu) and any anilato-type ligand (3,6-disubstituted-2,5-dihydroxy-1,4-benzoquinone dianion = C6O4X22−). We present all the anilato-Ln compounds [...] Read more.
In this review, we describe all the structurally characterized complexes containing lanthanoids (Ln, including La and group 3 metals: Y and Lu) and any anilato-type ligand (3,6-disubstituted-2,5-dihydroxy-1,4-benzoquinone dianion = C6O4X22−). We present all the anilato-Ln compounds including those where, besides the anilato-type ligand, there is one or more coligands or solvent molecules coordinated to the lanthanoid ions. We show the different structural types observed in these compounds: from discrete monomers, dimers and tetramers to extended 1D, 2D and 3D lattices with different topologies. We also revise the magnetic properties of these Ln-anilato compounds, including single-molecule magnet (SMM) and single-ion magnet (SIM) behaviours. Finally, we show the luminescent and electrochemical properties of some of them, their gas/solvent adsorption/absorption and exchange capacity and the attempts to prepare them as thin films. Full article
(This article belongs to the Special Issue Feature Papers in Magnetochemistry)
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7 pages, 2120 KiB  
Article
Fabrication and Magneto-Optical Property of (Dy0.7Y0.25La0.05)2O3 Transparent Ceramics by PLSH Technology
by Ding Zhou, Xiaohui Li, Tun Wang, Jiayue Xu, Zhanyong Wang, Ying Shi, Dmitry Permin and Stanislav S. Balabanov
Magnetochemistry 2020, 6(4), 70; https://doi.org/10.3390/magnetochemistry6040070 - 15 Dec 2020
Cited by 11 | Viewed by 2227
Abstract
(Dy0.7Y0.25La0.05)2O3 magneto-optical transparent ceramics were successfully fabricated by pressureless sintering in reductive H2 atmosphere (PLSH). The raw powder of (Dy0.7Y0.25La0.05)2O3 was synthesized by a [...] Read more.
(Dy0.7Y0.25La0.05)2O3 magneto-optical transparent ceramics were successfully fabricated by pressureless sintering in reductive H2 atmosphere (PLSH). The raw powder of (Dy0.7Y0.25La0.05)2O3 was synthesized by a modified self-propagating high-temperature synthesis (SHS) and sintered to transparent ceramics at 1400–1600 °C in a flowing H2 atmosphere, showing good sinterability of the as-synthesized raw powder. The magneto-optical Verdet constant of (Dy0.7Y0.25La0.05)2O3 transparent ceramics was measured to be −191.57 rad/(T·m) at a wavelength of 632.8 nm. In this magneto-optical material of (Dy0.7Y0.25La0.05)2O3, relative cheaper Dy and Y were used to replace Tb, and the low cost and good magneto-optical property showed the advantage of application on Faraday isolators (FIs) and Faraday rotators (FRs). Full article
(This article belongs to the Special Issue Magneto-Optical Ceramics)
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25 pages, 4853 KiB  
Review
When Molecular Magnetism Meets Supramolecular Chemistry: Multifunctional and Multiresponsive Dicopper(II) Metallacyclophanes as Proof-of-Concept for Single-Molecule Spintronics and Quantum Computing Technologies?
by Renato Rabelo, Salah-Eddine Stiriba, Danielle Cangussu, Cynthia L. M. Pereira, Nicolás Moliner, Rafael Ruiz-García, Joan Cano, Juan Faus, Yves Journaux and Miguel Julve
Magnetochemistry 2020, 6(4), 69; https://doi.org/10.3390/magnetochemistry6040069 - 4 Dec 2020
Cited by 12 | Viewed by 4432
Abstract
Molecular magnetism has made a long journey, from the fundamental studies on through-ligand electron exchange magnetic interactions in dinuclear metal complexes with extended organic bridges to the more recent exploration of their electron spin transport and quantum coherence properties. Such a field has [...] Read more.
Molecular magnetism has made a long journey, from the fundamental studies on through-ligand electron exchange magnetic interactions in dinuclear metal complexes with extended organic bridges to the more recent exploration of their electron spin transport and quantum coherence properties. Such a field has witnessed a renaissance of dinuclear metallacyclic systems as new experimental and theoretical models for single-molecule spintronics and quantum computing, due to the intercrossing between molecular magnetism and metallosupramolecular chemistry. The present review reports a state-of-the-art overview as well as future perspectives on the use of oxamato-based dicopper(II) metallacyclophanes as promising candidates to make multifunctional and multiresponsive, single-molecule magnetic (nano)devices for the physical implementation of quantum information processing (QIP). They incorporate molecular magnetic couplers, transformers, and wires, controlling and facilitating the spin communication, as well as molecular magnetic rectifiers, transistors, and switches, exhibiting a bistable (ON/OFF) spin behavior under external stimuli (chemical, electronic, or photonic). Special focus is placed on the extensive research work done by Professor Francesc Lloret, an outstanding chemist, excellent teacher, best friend, and colleague, in recognition of his invaluable contributions to molecular magnetism on the occasion of his 65th birthday. Full article
(This article belongs to the Section Spin Crossover and Spintronics)
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35 pages, 5019 KiB  
Review
Magnetite (Fe3O4) Nanoparticles in Biomedical Application: From Synthesis to Surface Functionalisation
by Lokesh Srinath Ganapathe, Mohd Ambri Mohamed, Rozan Mohamad Yunus and Dilla Duryha Berhanuddin
Magnetochemistry 2020, 6(4), 68; https://doi.org/10.3390/magnetochemistry6040068 - 3 Dec 2020
Cited by 253 | Viewed by 21539
Abstract
Nanotechnology has gained much attention for its potential application in medical science. Iron oxide nanoparticles have demonstrated a promising effect in various biomedical applications. In particular, magnetite (Fe3O4) nanoparticles are widely applied due to their biocompatibility, high magnetic susceptibility, [...] Read more.
Nanotechnology has gained much attention for its potential application in medical science. Iron oxide nanoparticles have demonstrated a promising effect in various biomedical applications. In particular, magnetite (Fe3O4) nanoparticles are widely applied due to their biocompatibility, high magnetic susceptibility, chemical stability, innocuousness, high saturation magnetisation, and inexpensiveness. Magnetite (Fe3O4) exhibits superparamagnetism as its size shrinks in the single-domain region to around 20 nm, which is an essential property for use in biomedical applications. In this review, the application of magnetite nanoparticles (MNPs) in the biomedical field based on different synthesis approaches and various surface functionalisation materials was discussed. Firstly, a brief introduction on the MNP properties, such as physical, thermal, magnetic, and optical properties, is provided. Considering that the surface chemistry of MNPs plays an important role in the practical implementation of in vitro and in vivo applications, this review then focuses on several predominant synthesis methods and variations in the synthesis parameters of MNPs. The encapsulation of MNPs with organic and inorganic materials is also discussed. Finally, the most common in vivo and in vitro applications in the biomedical world are elucidated. This review aims to deliver concise information to new researchers in this field, guide them in selecting appropriate synthesis techniques for MNPs, and to enhance the surface chemistry of MNPs for their interests. Full article
(This article belongs to the Special Issue Magnetic Nanoparticles 2020)
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33 pages, 4095 KiB  
Review
Electrocaloric Cooling: A Review of the Thermodynamic Cycles, Materials, Models, and Devices
by Adriana Greco and Claudia Masselli
Magnetochemistry 2020, 6(4), 67; https://doi.org/10.3390/magnetochemistry6040067 - 27 Nov 2020
Cited by 37 | Viewed by 7946
Abstract
Electrocaloric is a novel emerging not-in-kind cooling technology based on solid-state materials exhibiting the electrocaloric effect, i.e., the property of changing their temperature because of an adiabatic change in the intensity of the electric field applied. This technology has only attracted the interests [...] Read more.
Electrocaloric is a novel emerging not-in-kind cooling technology based on solid-state materials exhibiting the electrocaloric effect, i.e., the property of changing their temperature because of an adiabatic change in the intensity of the electric field applied. This technology has only attracted the interests of the scientific community in the last two decades, even though it has the main feature of being based on eco-friendly materials that, because of their solid-state nature, do not provide a direct contribution in global warming. Even if some steps have already been taken, the research fields connected to electrocaloric cooling are still open: The identification of the most appropriated thermodynamic cycle, electrocaloric refrigerants, as well as the development of efficient cooling systems. To this purpose, this review paper provides a snapshot of the electrocaloric world and compares the progress made by the inherent scientific community in all the connected fields: the thermodynamic cycles, materials, experimental devices, numerical models, energy performances and prospective cooling applications. Full article
(This article belongs to the Special Issue Magnetocaloric and Caloric Materials for Solid-State Cooling)
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20 pages, 3275 KiB  
Article
X-ray Structure and Magnetic Properties of Heterobimetallic Chains Based on the Use of an Octacyanidodicobalt(III) Complex as Metalloligand
by Maria-Gabriela Alexandru, Diana Visinescu, Sergiu Shova, Abdeslem Bentama, Francesc Lloret, Joan Cano and Miguel Julve
Magnetochemistry 2020, 6(4), 66; https://doi.org/10.3390/magnetochemistry6040066 - 27 Nov 2020
Cited by 4 | Viewed by 3440
Abstract
The assembly of [Co2III(μ-2,5-dpp)(CN)8]2− anions and [MII(CH3OH)2(DMSO)2]2+ cations resulted into the formation of two heterobimetallic 1D coordination polymers of formula [MII(CH3OH)2(DMSO)2 [...] Read more.
The assembly of [Co2III(μ-2,5-dpp)(CN)8]2− anions and [MII(CH3OH)2(DMSO)2]2+ cations resulted into the formation of two heterobimetallic 1D coordination polymers of formula [MII(CH3OH)2(DMSO)2(μ-NC)2Co2III(μ-2,5-dpp)(CN)6]n·4nCH3OH [M = CoII (1)/FeII (2) and 2,5-dpp = 2,5-bis(2-pyridyl)pyrazine. The [Co2III(μ-2,5-dpp)(CN)8]2− metalloligand coordinates the paramagnetic [MII(CH3OH)2(DMSO)2]2+ complex cations, in a bis-monodentate fashion, to give rise to neutral heterobimetallic chains. Cryomagnetic dc (1.9–300 K) and ac (2.0–13 K) magnetic measurements for 1 and 2 show the presence of Co(II)HS (1) and Fe(II)HS (2) ions (HS – high-spin), respectively, with D values of +53.7(5) (1) and −5.1(3) cm−1 (2) and slow magnetic relaxation for 1, this compound being a new example of SIM with transversal magnetic anisotropy. Low-temperature Q-band EPR study of 1 confirms that D value is positive, which reveals the occurrence of a strong asymmetry in the g-tensors and allows a rough estimation of the E/D ratio, whereas 2 is EPR silent. Theoretical calculations by CASSCF/NEVPT2 on 1 and 2 support the results from magnetometry and EPR. The analysis of the ac magnetic measurements of 1 shows that the relaxation of M takes place in the ground state under external magnetic dc fields through dominant Raman and direct spin-phonon processes. Full article
(This article belongs to the Special Issue Magnetic Coordination Polymers)
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20 pages, 2378 KiB  
Review
Explorations of Magnetic Properties of Noble Gases: The Past, Present, and Future
by Włodzimierz Makulski
Magnetochemistry 2020, 6(4), 65; https://doi.org/10.3390/magnetochemistry6040065 - 23 Nov 2020
Cited by 5 | Viewed by 4011
Abstract
In recent years, we have seen spectacular growth in the experimental and theoretical investigations of magnetic properties of small subatomic particles: electrons, positrons, muons, and neutrinos. However, conventional methods for establishing these properties for atomic nuclei are also in progress, due to new, [...] Read more.
In recent years, we have seen spectacular growth in the experimental and theoretical investigations of magnetic properties of small subatomic particles: electrons, positrons, muons, and neutrinos. However, conventional methods for establishing these properties for atomic nuclei are also in progress, due to new, more sophisticated theoretical achievements and experimental results performed using modern spectroscopic devices. In this review, a brief outline of the history of experiments with nuclear magnetic moments in magnetic fields of noble gases is provided. In particular, nuclear magnetic resonance (NMR) and atomic beam magnetic resonance (ABMR) measurements are included in this text. Various aspects of NMR methodology performed in the gas phase are discussed in detail. The basic achievements of this research are reviewed, and the main features of the methods for the noble gas isotopes: 3He, 21Ne, 83Kr, 129Xe, and 131Xe are clarified. A comprehensive description of short lived isotopes of argon (Ar) and radon (Rn) measurements is included. Remarks on the theoretical calculations and future experimental intentions of nuclear magnetic moments of noble gases are also provided. Full article
(This article belongs to the Special Issue Review Papers on Magnetic Resonances)
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14 pages, 2396 KiB  
Review
Spin Crossover and Magnetic-Dielectric Bistability Induced by Hidden Pseudo-Jahn–Teller Effect
by Isaac B. Bersuker
Magnetochemistry 2020, 6(4), 64; https://doi.org/10.3390/magnetochemistry6040064 - 22 Nov 2020
Cited by 3 | Viewed by 3161
Abstract
In a semi-review paper, we show that the hidden Jahn–Teller effect (JTE) and pseudo-JTE (PJTE) in molecular systems and solids, under certain conditions lead to the formation of two coexisting stable space configurations with different magnetic and dielectric properties, switchable by external perturbations. [...] Read more.
In a semi-review paper, we show that the hidden Jahn–Teller effect (JTE) and pseudo-JTE (PJTE) in molecular systems and solids, under certain conditions lead to the formation of two coexisting stable space configurations with different magnetic and dielectric properties, switchable by external perturbations. One of the stable configurations has a high space symmetry and a non-zero or higher spin (HS) (non-zero magnetic moment), the other being distorted, but with zero or lower spin (LS). The number of systems with hidden JTE or PJTE is innumerable; we demonstrate this on the (no exhaustible, too) group of systems with half-filed closed-shell degenerate electronic (orbital or band) configurations e2 and t3. The spin-crossover-change from the high symmetry HS arrangement to the low-symmetry LS geometry is accompanied by (driven by the PJTE) orbital disproportionation, in which the system prefers spins-paired states with two electrons on the same orbital (and lower symmetry charge distribution) over the Hund’s spin-parallel arrangement involving several orbitals. Ab initio calculations previously carried out on a series of molecular systems and clusters in crystals, including CuF3, Si3, Si4, Ge4, C4H4, Na4−, C603−, CuO6 (in two crystal environments, LiCuO2 and NaCuO2), etc., confirmed the general theory and allowed for estimates of the parameter values including relaxation times. The hidden JTE and PJTE are thus general tools for search and studies of polyatomic systems with bistabilities. Full article
(This article belongs to the Special Issue Stimuli-Responsive Magnetic Molecular Materials)
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10 pages, 5953 KiB  
Article
Fabrication and Magneto-Optical Properties of Yb2O3 Based Ceramics
by Dmitry A. Permin, Anastasia V. Novikova, Vitaly A. Koshkin, Stanislav S. Balabanov, Ilya L. Snetkov, Oleg V. Palashov and Ksenia E. Smetanina
Magnetochemistry 2020, 6(4), 63; https://doi.org/10.3390/magnetochemistry6040063 - 16 Nov 2020
Cited by 15 | Viewed by 2820
Abstract
Transparent ceramics based on ytterbium oxide have been successfully produced by vacuum sintering of self-propagating high-temperature synthesized powders with use of a La2O3 sintering aid. Phase composition and microstructure of the initial powders were studied by X-ray diffraction analysis and [...] Read more.
Transparent ceramics based on ytterbium oxide have been successfully produced by vacuum sintering of self-propagating high-temperature synthesized powders with use of a La2O3 sintering aid. Phase composition and microstructure of the initial powders were studied by X-ray diffraction analysis and scanning electron microscopy. It was found that addition of 5 mol.% of La2O3 does not cause formation of secondary phases in the Yb2O3 powders. The 4% La:Yb2O3 ceramics showed the best in-line transmittance of 73% at a wavelength of 2 μm among the studied samples. Dependence of the Verdet constant on wavelength was investigated in the range of 0.4–2 μm. The most promising finding is use of the obtained material as Faraday isolators in the wavelength region of ~1.5 μm, where there are no absorption bands, and the Verdet constant is 8.6 rad/(T*m). Full article
(This article belongs to the Special Issue Magneto-Optical Ceramics)
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11 pages, 748 KiB  
Article
Interplay of Jahn-Teller Ordering and Spin Crossover in Co(II) Compounds
by Sophia Klokishner and Serghei M. Ostrovsky
Magnetochemistry 2020, 6(4), 62; https://doi.org/10.3390/magnetochemistry6040062 - 16 Nov 2020
Cited by 2 | Viewed by 2420
Abstract
The spin crossover phenomena in Co(II) compounds are in the focus of the present paper. A microscopic theoretical approach for the description of spin transitions in mononuclear Co(II) compounds is suggested. Within the framework of this approach there are taken into account two [...] Read more.
The spin crossover phenomena in Co(II) compounds are in the focus of the present paper. A microscopic theoretical approach for the description of spin transitions in mononuclear Co(II) compounds is suggested. Within the framework of this approach there are taken into account two types of interionic interactions that may be operative in the problem such as the electron-deformational interaction and the cooperative Jahn-Teller interaction arising from the coupling of the low-spin state of the Co(II) ion with the tetragonal vibrations of the nearest surrounding. The different role of these interactions in the spin transformation is demonstrated and discussed. On the basis of developed approach a qualitative and quantitative explanation of the experimental data on the temperature dependence of the magnetic susceptibility for the [Co(pyterpy)2](PF6)2, [Co(pyterpy)2](TCNQ)2⋅DMF⋅MeOH and [Co(pyterpy)2](TCNQ)2⋅MeCN⋅MeOH compounds is given. Full article
(This article belongs to the Special Issue Stimuli-Responsive Magnetic Molecular Materials)
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10 pages, 1749 KiB  
Article
The Magnetic Band-Structures of Ordered PtxFe1−x, PtxCo1−x, and PtxNi1−x (x = 0.25, 0.50, and 0.75)
by Ian Shuttleworth
Magnetochemistry 2020, 6(4), 61; https://doi.org/10.3390/magnetochemistry6040061 - 13 Nov 2020
Cited by 12 | Viewed by 2479
Abstract
The electronic band structures of the ordered L12 and L10 phases of the PtxM1−x (M = Fe, Co and Ni) alloys were investigated using spin-polarized density functional theory (DFT). The relative contributions of both itinerant (Stoner) and localized [...] Read more.
The electronic band structures of the ordered L12 and L10 phases of the PtxM1−x (M = Fe, Co and Ni) alloys were investigated using spin-polarized density functional theory (DFT). The relative contributions of both itinerant (Stoner) and localized magnetism at the high-symmetry k-points were determined and discussed qualitatively. Significant directional effects were identified along the A and R directions of the L10 and L12 alloys, respectively, and are discussed in terms of charge channeling effects. Full article
(This article belongs to the Special Issue Feature Papers in Magnetochemistry)
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26 pages, 12566 KiB  
Article
Ten-Coordinate Lanthanide [Ln(HL)(L)] Complexes (Ln = Dy, Ho, Er, Tb) with Pentadentate N3O2-Type Schiff-Base Ligands: Synthesis, Structure and Magnetism
by Tamara A. Bazhenova, Ilya A. Yakushev, Konstantin A. Lyssenko, Olga V. Maximova, Vladimir S. Mironov, Yuriy V. Manakin, Alexey B. Kornev, Alexander N. Vasiliev and Eduard B. Yagubskii
Magnetochemistry 2020, 6(4), 60; https://doi.org/10.3390/magnetochemistry6040060 - 13 Nov 2020
Cited by 10 | Viewed by 3843
Abstract
A series of five neutral mononuclear lanthanide complexes [Ln(HL)(L)] (Ln = Dy3+, Ho3+ Er3+ and Tb3+) with rigid pentadentate N3O2-type Schiff base ligands, H2LH (1-Dy, 3-Ho, 4-Er [...] Read more.
A series of five neutral mononuclear lanthanide complexes [Ln(HL)(L)] (Ln = Dy3+, Ho3+ Er3+ and Tb3+) with rigid pentadentate N3O2-type Schiff base ligands, H2LH (1-Dy, 3-Ho, 4-Er and 6-Tb complexes) or H2LOCH3, (2-Dy complex) has been synthesized by reaction of two equivalents of 1,1′-(pyridine-2,6-diyl)bis(ethan-1-yl-1-ylidene))dibenzohydrazine (H2LH, [H2DAPBH]) or 1,1′-(pyridine-2,6-diyl)bis(ethan-1-yl-1-ylidene))di-4-methoxybenzohydrazine (H2LOCH3, [H2DAPMBH]) with common lanthanide salts. The terbium complex [Tb(LH)(NO3)(H2O)2](DME)2 (5-Tb) with one ligand H2LH was also obtained and characterized. Single crystal X-ray analysis shows that complexes 1–4 have the composition {[Ln3+(HL)−(L)2−] solv} and similar molecular structures. In all the compounds, the central Ln3+ ion is chelated by two interlocked pentadentate ligands resulting in the coordination number of ten. Each lanthanide ion is coordinated by six nitrogen atoms and four oxygen atoms of the two N3O2 chelating groups forming together a distorted bicapped square antiprismatic polyhedron N6O4 with two capping pyridyl N atoms in the apical positions. The ac magnetic measurements reveal field-induced single-molecule magnet (SMM) behavior of the two dysprosium complexes (with barriers of Ueff = 29 K at 800 Oe in 1-Dy and Ueff = 70 K at 300 Oe in 2-Dy) and erbium complex (Ueff = 87 K at 1500 Oe in 4-Er); complex 3-Ho with a non-Kramers Ho3+ ion is SMM-silent. Although 2-Dy differs from 1-Dy only by a distant methoxy-group in the phenyl ring of the ligand, their dynamic magnetic properties are markedly different. This feature can be due to the difference in long-range contributions (beyond the first coordination sphere) to the crystal-field (CF) potential of 4f electrons of Dy3+ ion that affects magnetic characteristics of the ground and excited CF states. Magnetic behavior and the electronic structure of Ln3+ ions of 1–4 complexes are analyzed in terms of CF calculations. Full article
(This article belongs to the Section Magnetic Materials)
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21 pages, 2814 KiB  
Article
Insights into Nature of Magnetization Plateaus of a Nickel Complex [Ni4(μ-CO3)2(aetpy)8](ClO4)4 from a Spin-1 Heisenberg Diamond Cluster
by Katarína Karl’ová, Jozef Strečka, Jozef Haniš and Masayuki Hagiwara
Magnetochemistry 2020, 6(4), 59; https://doi.org/10.3390/magnetochemistry6040059 - 12 Nov 2020
Cited by 7 | Viewed by 3098
Abstract
Magnetic and magnetocaloric properties of a spin-1 Heisenberg diamond cluster with two different coupling constants are investigated with the help of an exact diagonalization based on the Kambe’s method, which employs a local conservation of composite spins formed by spin-1 entities located in [...] Read more.
Magnetic and magnetocaloric properties of a spin-1 Heisenberg diamond cluster with two different coupling constants are investigated with the help of an exact diagonalization based on the Kambe’s method, which employs a local conservation of composite spins formed by spin-1 entities located in opposite corners of a diamond spin cluster. It is shown that the spin-1 Heisenberg diamond cluster exhibits several intriguing quantum ground states, which are manifested in low-temperature magnetization curves as intermediate plateaus at 1/4, 1/2, and 3/4 of the saturation magnetization. In addition, the spin-1 Heisenberg diamond cluster may also exhibit an enhanced magnetocaloric effect, which may be relevant for a low-temperature refrigeration achieved through the adiabatic demagnetization. It is evidenced that the spin-1 Heisenberg diamond cluster with the antiferromagnetic coupling constants J1/kB = 41.4 K and J2/kB = 9.2 K satisfactorily reproduces a low-temperature magnetization curve recorded for the tetranuclear nickel complex [Ni4(μ-CO3)2(aetpy)8](ClO4)4 (aetpy = 2-aminoethyl-pyridine) including a size and position of intermediate plateaus detected at 1/2 and 3/4 of the saturation magnetization. A microscopic nature of fractional magnetization plateaus observed experimentally is clarified and interpreted in terms of valence-bond crystal with either a single or double valence bond. It is suggested that this frustrated magnetic molecule can provide a prospective cryogenic coolant with the maximal isothermal entropy change −ΔSM=10.6 J·K−1·kg−1 in a temperature range below 2.3 K. Full article
(This article belongs to the Special Issue Modern Magnetic Systems: Theory and Experiment in Concert)
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10 pages, 1710 KiB  
Article
Ligand Control of 59Co Nuclear Spin Relaxation Thermometry
by Tyler M. Ozvat, Spencer H. Johnson, Anthony K. Rappé and Joseph M. Zadrozny
Magnetochemistry 2020, 6(4), 58; https://doi.org/10.3390/magnetochemistry6040058 - 12 Nov 2020
Cited by 5 | Viewed by 2860
Abstract
Studying the correlation between temperature-driven molecular structure and nuclear spin dynamics is essential to understanding fundamental design principles for thermometric nuclear magnetic resonance spin-based probes. Herein, we study the impact of progressively encapsulating ligands on temperature-dependent 59Co T1 (spin–lattice) and T [...] Read more.
Studying the correlation between temperature-driven molecular structure and nuclear spin dynamics is essential to understanding fundamental design principles for thermometric nuclear magnetic resonance spin-based probes. Herein, we study the impact of progressively encapsulating ligands on temperature-dependent 59Co T1 (spin–lattice) and T2 (spin–spin) relaxation times in a set of Co(III) complexes: K3[Co(CN)6] (1); [Co(NH3)6]Cl3 (2); [Co(en)3]Cl3 (3), en = ethylenediamine); [Co(tn)3]Cl3 (4), tn = trimethylenediamine); [Co(tame)2]Cl3 (5), tame = triaminomethylethane); and [Co(dinosar)]Cl3 (6), dinosar = dinitrosarcophagine). Measurements indicate that 59Co T1 and T2 increase with temperature for 1–6 between 10 and 60 °C, with the greatest ΔT1/ΔT and ΔT2/ΔT temperature sensitivities found for 4 and 3, 5.3(3)%T1/°C and 6(1)%T2/°C, respectively. Temperature-dependent T2* (dephasing time) analyses were also made, revealing the highest ΔT2*/ΔT sensitivities in structures of greatest encapsulation, as high as 4.64%T2*/°C for 6. Calculations of the temperature-dependent quadrupolar coupling parameter, Δe2qQ/ΔT, enable insight into the origins of the relative ΔT1/ΔT values. These results suggest tunable quadrupolar coupling interactions as novel design principles for enhancing temperature sensitivity in nuclear spin-based probes. Full article
(This article belongs to the Section Magnetic Resonances)
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10 pages, 3313 KiB  
Article
Non-Volatile Regulation of Magnetism via Electric Fields in Polycrystal FeSi/(011) PMN-0.32PT Heterostructures
by Xiaobin Guo, Fengchao Su, Xiaoling Lu, Xingui Tang, Zhenhua Tang, Wenhua Li, Yanping Jiang, Qiuxiang Liu, Yalu Zuo and Li Xi
Magnetochemistry 2020, 6(4), 57; https://doi.org/10.3390/magnetochemistry6040057 - 10 Nov 2020
Cited by 1 | Viewed by 2290
Abstract
The choice and configuration of the ferroelectric (FE) substrate and the ferromagnetic (FM) layer in FM/FE heterostructures play an important role in magnetism modification with regard to amplitude and efficiency. In this study, we fabricated FeSi films on low crystalline (011) [Pb(Mg1/3 [...] Read more.
The choice and configuration of the ferroelectric (FE) substrate and the ferromagnetic (FM) layer in FM/FE heterostructures play an important role in magnetism modification with regard to amplitude and efficiency. In this study, we fabricated FeSi films on low crystalline (011) [Pb(Mg1/3Nb2/3)O3]0.7-[PbTiO3]0.3 (PMN-0.32PT) using radio frequency magnetron sputtering. In the annealed FeSi/(011) PMN-0.32PT heterostructures, the FeSi film presented with a (011) preferred orientated polycrystalline structure and low magnetocrystalline anisotropy. Both loop-like and butterfly-like magnetism modifications were observed by applying bipolar electric fields, and the weak and abnormal electrically mediated magnetism behaviors were significantly different from the prominent magnetic anisotropy transition in FeSi/(011) PMN-0.3PT. The comparative analyses suggest that the resulting high-quality single-crystalline PMN-xPT and FM films with low coercivity are of great significance for exploring giant, reversible, and non-volatile magnetism regulation. Full article
(This article belongs to the Special Issue Emerging Applications and Developments in Spin Crossover Systems)
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16 pages, 7357 KiB  
Article
Effect of Single-Ion Anisotropy on Magnetocaloric Properties of Frustrated Spin-s Ising Nanoclusters
by Mariia Mohylna and Milan Žukovič
Magnetochemistry 2020, 6(4), 56; https://doi.org/10.3390/magnetochemistry6040056 - 1 Nov 2020
Cited by 7 | Viewed by 2506
Abstract
Effects of a single-ion anisotropy on magnetocaloric properties of selected spin-s≥1 antiferromagnetic Ising clusters with frustration-inducing triangular geometry are studied by exact enumeration. It is found that inclusion of the single-ion anisotropy parameter D can result in a much more [...] Read more.
Effects of a single-ion anisotropy on magnetocaloric properties of selected spin-s≥1 antiferromagnetic Ising clusters with frustration-inducing triangular geometry are studied by exact enumeration. It is found that inclusion of the single-ion anisotropy parameter D can result in a much more complex ground-state behavior, which is also reflected in a magnetocaloric effect (MCE) at finite temperatures. For negative D (easy-plane anisotropy) with increasing s, the ground-state magnetization as a function of the external field gradually shows increasing number of plateaus of various heights. Except for the cases of integer s with D<D0≤0, the first magnetization plateau is of non-zero height. This property facilitates an enhanced MCE in the adiabatic demagnetization process in the form of an abrupt decrease in temperature as the magnetic field vanishes to zero. The cooling rate can be considerably enhanced in the systems with larger s and D>0 (easy-axis anisotropy), albeit its dependence on these parameters is strongly dependent on the cluster geometry. From the studied systems more favorable conditions for observing a giant MCE were found in the 2CS cluster, consisting of two corner-sharing tetrahedra, the experimental realization of which could be technologically used for efficient refrigeration to ultra-low temperatures. Full article
(This article belongs to the Special Issue Modern Magnetic Systems: Theory and Experiment in Concert)
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16 pages, 3976 KiB  
Article
S-Functionalized Tripods with Monomethylene Spacers: Routes to Tetrairon(III) Single-Molecule Magnets with Ultrashort Tethering Groups
by Andrea Cornia, Chiara Danieli, Fabio Meglioli, Erik Tancini, Alessio Nicolini, Maria Jesus Rodriguez-Douton, Anne-Laure Barra, Marco Affronte and Roberta Sessoli
Magnetochemistry 2020, 6(4), 55; https://doi.org/10.3390/magnetochemistry6040055 - 30 Oct 2020
Cited by 2 | Viewed by 2744
Abstract
The organization of single-molecule magnets (SMMs) on surfaces is a mainstream research path in molecular magnetism. Of special importance is the control of grafting geometry in chemisorbed monolayers on metal surfaces. We herein present the synthesis, solid-state structure, and magnetic characterization of propeller-like [...] Read more.
The organization of single-molecule magnets (SMMs) on surfaces is a mainstream research path in molecular magnetism. Of special importance is the control of grafting geometry in chemisorbed monolayers on metal surfaces. We herein present the synthesis, solid-state structure, and magnetic characterization of propeller-like tetrairon(III) SMMs containing the shortest-reported tethering groups for gold surfaces. Functionalization of molecular structure is attained using 2-R-2-(hydroxymethyl)propane-1,3-diol tripodal proligands (H3LR). The R substituents comprise a monomethylene spacer and three different terminations known to act as stable precursors of S-Au bonds (R = CH2SCN, CH2SAc and CH2SSnBu). These chemical groups are shown to be chemically compatible with the tetrairon(III) core and to afford fully-functional SMMs in crystalline form and in fair to excellent yields. Full article
(This article belongs to the Section Molecular Magnetism)
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9 pages, 3291 KiB  
Article
A New FeIII Substituted Arsenotungstate [FeIII2(AsIIIW6O23)2(AsIIIO3H)2]12−: Synthesis, Structure, Characterization and Magnetic Properties
by Masooma Ibrahim, Yan Peng and Christopher E. Anson
Magnetochemistry 2020, 6(4), 54; https://doi.org/10.3390/magnetochemistry6040054 - 25 Oct 2020
Cited by 2 | Viewed by 2997
Abstract
The iron(III)-containing arsenotungstate [FeIII2(AsIIIW6O23)2(AsIIIO3H)2]12− (1) was prepared via a simple, one-pot reaction in aqueous basic medium. The compound was isolated as its sodium [...] Read more.
The iron(III)-containing arsenotungstate [FeIII2(AsIIIW6O23)2(AsIIIO3H)2]12− (1) was prepared via a simple, one-pot reaction in aqueous basic medium. The compound was isolated as its sodium salt, and structurally-characterized by Single Crystal X-ray Diffraction (SCXRD), Powder X-ray Diffraction (PXRD), Fourier-Transform Infrared (FT-IR) spectroscopy, Thermogravimetric Analysis (TGA) and elemental analysis. Its magnetic properties are reported; the antiferromagnetic coupling between the two FeIII centers is unusually weak as a result of the bridging geometry imposed by the rigid arsenotungstate metalloligands. Full article
(This article belongs to the Special Issue Paramagnetic Metal Ion-Containing Polyoxometalates)
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14 pages, 1418 KiB  
Article
Crystal Structure and Magnetic Properties of Peacock–Weakley Type Polyoxometalates Na9[Ln(W5O18)2] (Ln = Tm, Yb): Rare Example of Tm(III) SMM
by Oleksandra Yu. Mariichak, Sandra Kaabel, Yevgen A. Karpichev, Georgiy M. Rozantsev, Serhii V. Radio, Céline Pichon, Hélène Bolvin and Jean-Pascal Sutter
Magnetochemistry 2020, 6(4), 53; https://doi.org/10.3390/magnetochemistry6040053 - 21 Oct 2020
Cited by 9 | Viewed by 4346
Abstract
We report Peacock–Weakley complexes, Na9[Ln(W5O18)2]∙35H2O, formed with Tm(III), 1, and Yb(III), 2. Their syntheses, physico-chemical characterizations, crystal structures, and magnetic properties are described. Ab initio calculations are also reported. These polyoxometalate [...] Read more.
We report Peacock–Weakley complexes, Na9[Ln(W5O18)2]∙35H2O, formed with Tm(III), 1, and Yb(III), 2. Their syntheses, physico-chemical characterizations, crystal structures, and magnetic properties are described. Ab initio calculations are also reported. These polyoxometalate (POM) complexes were obtained using original synthetic conditions where acidification was performed with a stoichiometric amount of nitric acid to an acidity of Z = ν(H+)/ν(WO42–) = 8/10 = 0.80. Both the Tm(III) and Yb(III) derivatives were found to exhibit field-induced slow relaxation of their magnetization likely controlled by Raman and Orbach relaxation processes. 1 is a rare example of a Tm(III)-based single-molecule magnet (SMM) and is a consequence of the oblate tetragonal anti-prismatic symmetry of the coordination sphere. Full article
(This article belongs to the Special Issue From Magnetic Anisotropy to Molecular Magnets: Theory and Experiments)
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24 pages, 5157 KiB  
Article
Pulse Magnetic Fields Induced Drug Release from Gold Coated Magnetic Nanoparticle Decorated Liposomes
by Basanta Acharya and Viktor Chikan
Magnetochemistry 2020, 6(4), 52; https://doi.org/10.3390/magnetochemistry6040052 - 19 Oct 2020
Cited by 10 | Viewed by 4186
Abstract
Magnetic nanoparticle-assisted drug release from liposomes is an important way to enhance the functionality/usefulness of liposomes. This work demonstrates an approach how to integrate magnetic nanoparticles with liposomes with the assistance of gold–thiol chemistry. The gold coated magnetic particles cover the thiolated liposomes [...] Read more.
Magnetic nanoparticle-assisted drug release from liposomes is an important way to enhance the functionality/usefulness of liposomes. This work demonstrates an approach how to integrate magnetic nanoparticles with liposomes with the assistance of gold–thiol chemistry. The gold coated magnetic particles cover the thiolated liposomes from the outside, which removes the competition of the drug molecules and the triggering magnetic particles to free the inner space of the liposomes when compared to previous magneto liposome formulations. The liposome consists of dipalmitoyl phosphatidylcholine (DPPC) combined with distearoylphosphatidylcholine (DSPC) in addition to regular cholesterol or cholesterol-PEG-SH. Permeability assays and electron microscopy images show efficient coupling between the liposomes and nanoparticles in the presence of thiol groups without compromising the functionality of the liposomes. The nanoparticles such as gold nanoparticles, gold coated iron oxide nanoparticles and bare iron oxide nanoparticles are added following the model drug encapsulation. The efficient coupling between the gold coated nanoparticles (NPs) and the thiolate liposomes is evidenced by the shift in transition temperature of the thiolated liposomes. The addition of magnetically triggerable nanoparticles externally makes the entire interior of liposomes available for drug loading. The drug release efficiencies of these liposomes/NPs complexes were compared under exposure to pulsed magnetic fields. The results indicate up to 20% of the drug can be released in short time, which is comparable in efficiency to previous studies performed when magnetic NPs were located inside liposomes. Interestingly, the liposomes were found to exhibit variations in release efficiency based on different dilution media which is attributed to an osmotic pressure effect on liposomal stability. Full article
(This article belongs to the Special Issue Magnetic Nanoparticles 2020)
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13 pages, 546 KiB  
Article
Eliashberg Theory of a Multiband Non-Phononic Spin Glass Superconductor
by Giovanni Alberto Ummarino
Magnetochemistry 2020, 6(4), 51; https://doi.org/10.3390/magnetochemistry6040051 - 16 Oct 2020
Viewed by 2616
Abstract
I solved the Eliashberg equations for a multiband non-phononic s± wave spin-glass superconductor, calculating the temperature dependence of the gaps and of superfluid density. Their behaviors were revealed to be unusual: showing non-monotonic temperature dependence and reentrant superconductivity. By considering particular input [...] Read more.
I solved the Eliashberg equations for a multiband non-phononic s± wave spin-glass superconductor, calculating the temperature dependence of the gaps and of superfluid density. Their behaviors were revealed to be unusual: showing non-monotonic temperature dependence and reentrant superconductivity. By considering particular input parameters values that could describe the iron pnictide EuFe2(As1−xPx)2, a rich and complex phase diagram arises, with two different ranges of temperature in which superconductivity appears. Full article
(This article belongs to the Special Issue Superconductivity and Magnetism)
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8 pages, 1096 KiB  
Article
Domain Structure and Reversal Mechanisms through Diffracted Magneto-optics in Fe80B20 Microsquare Arrays
by Ruben Álvarez-Sánchez, Jose Miguel García-Martín, Fernando Briones and José Luis Costa-Krämer
Magnetochemistry 2020, 6(4), 50; https://doi.org/10.3390/magnetochemistry6040050 - 13 Oct 2020
Cited by 1 | Viewed by 2247
Abstract
In this paper, the predictive power of diffracxtive magneto-optics concerning domain structure and reversal mechanisms in ordered arrays of magnetic elements is demonstrated. A simple theoretical model based on Fraunhoffer diffraction theory is used to predict the magnetisation reversal mechanisms in an array [...] Read more.
In this paper, the predictive power of diffracxtive magneto-optics concerning domain structure and reversal mechanisms in ordered arrays of magnetic elements is demonstrated. A simple theoretical model based on Fraunhoffer diffraction theory is used to predict the magnetisation reversal mechanisms in an array of magnetic elements. Different domain structures and simplified models (or educated guesses) of the associated reversal mechanisms produce marked differences in the spatial distributions of the magnetisation. These differences and the associated magnetisation distribution moments are experimentally accessible through conventional and diffractive magneto-optical Kerr effect measurements. The domain and magnetisation reversal predictions are corroborated with Magnetic Force Microscopy (MFM) measurements. Full article
(This article belongs to the Special Issue Interactions and Magneto-Optics in Magnetic Arrays)
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47 pages, 4932 KiB  
Review
Recent Advances in Magnetic Nanoparticles and Nanocomposites for the Remediation of Water Resources
by Joseph Govan
Magnetochemistry 2020, 6(4), 49; https://doi.org/10.3390/magnetochemistry6040049 - 9 Oct 2020
Cited by 31 | Viewed by 5264
Abstract
Water resources are of extreme importance for both human society and the environment. However, human activity has increasingly resulted in the contamination of these resources with a wide range of materials that can prevent their use. Nanomaterials provide a possible means to reduce [...] Read more.
Water resources are of extreme importance for both human society and the environment. However, human activity has increasingly resulted in the contamination of these resources with a wide range of materials that can prevent their use. Nanomaterials provide a possible means to reduce this contamination, but their removal from water after use may be difficult. The addition of a magnetic character to nanomaterials makes their retrieval after use much easier. The following review comprises a short survey of the most recent reports in this field. It comprises five sections, an introduction into the theme, reports on single magnetic nanoparticles, magnetic nanocomposites containing two of more nanomaterials, magnetic nanocomposites containing material of a biologic origin and finally, observations about the reported research with a view to future developments. This review should provide a snapshot of developments in what is a vibrant and fast-moving area of research. Full article
(This article belongs to the Section Magnetic Nanospecies)
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11 pages, 4787 KiB  
Article
Nitronyl Nitroxide Biradical-Based Binuclear Lanthanide Complexes: Structure and Magnetic Properties
by Lu Xi, Jing Han, Xiaohui Huang and Licun Li
Magnetochemistry 2020, 6(4), 48; https://doi.org/10.3390/magnetochemistry6040048 - 3 Oct 2020
Cited by 5 | Viewed by 3162
Abstract
Employing a new nitronyl nitroxide biradical NITPhPzbis(NITPhPzbis = 5-(1-pyrazolyl)-1,3-bis(1’-oxyl-3’-oxido-4’,4’,5’,5’-tetramethyl-4,5-hydro-1H-imidazol-2-yl)benzene), a series of 2p-4f complexes [Ln2(hfac)6(H2O)(NITPhPzbis)] (LnIII = Gd1, Tb2, Dy3; hfac = hexafluoroacetylacetonate) were successfully [...] Read more.
Employing a new nitronyl nitroxide biradical NITPhPzbis(NITPhPzbis = 5-(1-pyrazolyl)-1,3-bis(1’-oxyl-3’-oxido-4’,4’,5’,5’-tetramethyl-4,5-hydro-1H-imidazol-2-yl)benzene), a series of 2p-4f complexes [Ln2(hfac)6(H2O)(NITPhPzbis)] (LnIII = Gd1, Tb2, Dy3; hfac = hexafluoroacetylacetonate) were successfully synthesized. In complexes 1–3, the designed biradical NITPhPzbis coordinates with two LnIII ions in chelating and bridging modes to form a four-spin binuclear structure. Direct-current magnetic study of Gd analogue indicates that ferromagnetic exchange exists between the Gd ion and the radical while antiferromagnetic coupling dominates between two mono-radicals. Dynamic magnetic data show that the χ” signals of complex 3 exhibit frequency dependence under zero field, demonstrating slow magnetic relaxation behavior in complex 3. And the estimated values of Ueff and τ0 are about 8.4 K and 9.1 × 10−8 s, respectively. Full article
(This article belongs to the Special Issue From Magnetic Anisotropy to Molecular Magnets: Theory and Experiments)
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12 pages, 16302 KiB  
Article
Finite Length Effects on Switching Mechanisms in Chains of Magnetic Particles
by Dominika Kuźma and Piotr Zieliński
Magnetochemistry 2020, 6(4), 47; https://doi.org/10.3390/magnetochemistry6040047 - 1 Oct 2020
Cited by 4 | Viewed by 2690
Abstract
Periodic systems of magnetic nanoparticles are now of interest as they support GHz spin waves. Their equilibrium configurations, switchable with the external magnetic field, are crucial for such applications. We study infinite and finite chains of particles of two shapes (i) ellipsoidal and [...] Read more.
Periodic systems of magnetic nanoparticles are now of interest as they support GHz spin waves. Their equilibrium configurations, switchable with the external magnetic field, are crucial for such applications. We study infinite and finite chains of particles of two shapes (i) ellipsoidal and (ii) rectangular stripes with long axes perpendicular to the chain axis. A variable magnetic field is applied parallel to the long axes. Micromagnetic simulations are compared with the corresponding discrete spin models (Stoner-Wohlfarth model, S-W). An antiferromagnetic configuration is the ground state for all the systems at vanishing field but a ferromagnetic configuration occurs when the field is strong enough. The switching of the infinite chains to the reversed ferromagnetic configuration proceeds directly for the ellipsoids and by an intermediate configuration, in which the magnetization within the particle is non-uniform, in the case of the stripes. The non-uniform configurations are well represented by tilted states in S-W model. Important differences are found in the finite analogs: the switching of ellipsoids becomes multistage and starts from the innermost particles relatively well reproduced with S-W model, whereas the reversal of the stripes, starts from the outermost particles and has no analog in S-W model. Practical consequences of the findings are discussed. Full article
(This article belongs to the Special Issue Feature Papers in Magnetochemistry)
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21 pages, 1834 KiB  
Review
Paramagnetic NMR Spectroscopy Is a Tool to Address Reactivity, Structure, and Protein–Protein Interactions of Metalloproteins: The Case of Iron–Sulfur Proteins
by Mario Piccioli
Magnetochemistry 2020, 6(4), 46; https://doi.org/10.3390/magnetochemistry6040046 - 26 Sep 2020
Cited by 12 | Viewed by 4532
Abstract
The study of cellular machineries responsible for the iron–sulfur (Fe–S) cluster biogenesis has led to the identification of a large number of proteins, whose importance for life is documented by an increasing number of diseases linked to them. The labile nature of Fe–S [...] Read more.
The study of cellular machineries responsible for the iron–sulfur (Fe–S) cluster biogenesis has led to the identification of a large number of proteins, whose importance for life is documented by an increasing number of diseases linked to them. The labile nature of Fe–S clusters and the transient protein–protein interactions, occurring during the various steps of the maturation process, make their structural characterization in solution particularly difficult. Paramagnetic nuclear magnetic resonance (NMR) has been used for decades to characterize chemical composition, magnetic coupling, and the electronic structure of Fe–S clusters in proteins; it represents, therefore, a powerful tool to study the protein–protein interaction networks of proteins involving into iron–sulfur cluster biogenesis. The optimization of the various NMR experiments with respect to the hyperfine interaction will be summarized here in the form of a protocol; recently developed experiments for measuring longitudinal and transverse nuclear relaxation rates in highly paramagnetic systems will be also reviewed. Finally, we will address the use of extrinsic paramagnetic centers covalently bound to diamagnetic proteins, which contributed over the last twenty years to promote the applications of paramagnetic NMR well beyond the structural biology of metalloproteins. Full article
(This article belongs to the Special Issue Nuclear Magnetic Resonance Spectroscopy in Biomedical Application)
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11 pages, 1894 KiB  
Article
Slow Magnetic Relaxation in a One-Dimensional Coordination Polymer Constructed from Hepta-Coordinate Cobalt(II) Nodes
by Amit Kumar Mondal, Arpan Mondal and Sanjit Konar
Magnetochemistry 2020, 6(4), 45; https://doi.org/10.3390/magnetochemistry6040045 - 23 Sep 2020
Cited by 11 | Viewed by 3134
Abstract
A one-dimensional coordination polymer was synthesized employing hepta-coordinate CoII as nodes and dicyanamide as linkers. Detailed direct current (DC) and alternating current (AC) magnetic susceptibility measurements reveal the presence of field-induced slow magnetic relaxation behavior of the magnetically isolated seven-coordinate CoII [...] Read more.
A one-dimensional coordination polymer was synthesized employing hepta-coordinate CoII as nodes and dicyanamide as linkers. Detailed direct current (DC) and alternating current (AC) magnetic susceptibility measurements reveal the presence of field-induced slow magnetic relaxation behavior of the magnetically isolated seven-coordinate CoII center with an easy-plane magnetic anisotropy. Detailed ab initio calculations were performed to understand the magnetic relaxation processes. To our knowledge, the reported complex represents the first example of slow magnetic relaxation in a one-dimensional coordination polymer constructed from hepta-coordinate CoII nodes and dicyanamide linkers. Full article
(This article belongs to the Special Issue Transition Metal (3d,4d,5d) and Lanthanide(III) Based Complexes and Coordination Polymers Showing Single-Molecule Magnet Behaviour)
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