Magnetochemistry

15 pages, 3433 KiB

Open AccessArticle

Comprehensively Understanding the Transformation of Paramagnetic Tetramer to Spin-Paired Dimer in an S = ½ Molecular Crystal

by Yin Qian, Yan Gao, Lei Xu, Reinhard K. Kremer, Jin Zhang and Xiao-Ming Ren

Magnetochemistry 2025, 11(2), 8; https://doi.org/10.3390/magnetochemistry11020008 - 24 Jan 2025

Abstract

In this study, we comparatively analyzed the variable-temperature crystal structures for two isomorphous salts, [1-benzyl-4-aminopyridinium][M(mnt)₂] (M = Ni or Cu; mnt²⁻ = maleonitriledithiolate; labeled as APy-Ni or APy-Cu). Both salts crystallize in the triclinic P–1 space group at [...] Read more.

In this study, we comparatively analyzed the variable-temperature crystal structures for two isomorphous salts, [1-benzyl-4-aminopyridinium][M(mnt)₂] (M = Ni or Cu; mnt²⁻ = maleonitriledithiolate; labeled as APy-Ni or APy-Cu). Both salts crystallize in the triclinic P–1 space group at 296 K, comprising linear [M(mnt)₂]⁻ (M = Ni or Cu) tetramers. A magnetostructural phase transition occurs at T_C~190 K in S = ½ APy-Ni at ambient pressure, with a conversion of paramagnetic tetramers into nonmagnetic spin-paired dimers. The discontinuous alteration of cell parameters at T_C signifies the characteristic of first-order phase transition in APy-Ni. No such transition appears in the nonmagnetic APy-Cu within the same temperature vicinity, demonstrating the magnetic interactions promoting the structural phase transition in APy-Ni, which is further reinforced through a comparison of the lattice formation energy between APy-Ni and APy-Cu. The phase transition may bear a resemblance to the mechanisms typically observed in spin-Peierls systems. We further explored the magnetic and phase transition properties of APy-Ni under varying pressures. Significantly, T_C shows a linear increase with rising pressure within the range of 0.003–0.88 GPa, with a rate of 90 K GPa⁻¹, manifesting that the applied pressure promotes the transition from tetramer to dimer. 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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11 pages, 2792 KiB

Open AccessArticle

Enhancement of Spin Wave Transmission Through Antiferromagnet in Pt/NiO/CoFeB Heterostructure

by Wei Shi, Yangkai Wang, Zhixin Liu, Yilin Pei, Qiuping Huang, Zhengping Fu, Jianlin Wang and Yalin Lu

Magnetochemistry 2025, 11(2), 7; https://doi.org/10.3390/magnetochemistry11020007 - 22 Jan 2025

Abstract

A significant enhancement of the spin current transmission through the antiferromagnetic insulating material NiO in Pt/NiO/CoFeB heterostructures was observed in this work. The ultrafast spin currents excited by laser pulses were injected into the Pt layers after passing through the NiO layers, and [...] Read more.

A significant enhancement of the spin current transmission through the antiferromagnetic insulating material NiO in Pt/NiO/CoFeB heterostructures was observed in this work. The ultrafast spin currents excited by laser pulses were injected into the Pt layers after passing through the NiO layers, and then transient charge currents were generated via the inverse spin Hall effect (ISHE), leading to a terahertz (THz) emission from the structure. The emitted THz signals were measured using electro-optic sampling with a ZnTe crystal. Thin NiO layers remarkably enhanced the THz signal amplitude, suggesting high spin transfer efficiency in NiO, and lighting a direction to ameliorate the spintronic THz emitter. The variable temperature measurements showed the amplitude had a maximum near the Néel temperature (T_N) of the NiO layer with a specific thickness. The results of phase difference suggested that the coherent evanescent spin wave-mediated transmission had a contribution below the T_N of the NiO layer, while the thermal magnon-mediated transmission existed at all temperatures. Our results not only achieve an enhancement in the spintronic THz source but also provide a THz spectroscopic method to investigate the dynamics of the ultrafast spintronic phenomenon. Full article

(This article belongs to the Special Issue Spin Waves in Magnonic Crystals and Hybrid Ferromagnetic Structures)

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38 pages, 16698 KiB

Open AccessArticle

Laudatio: Miguel Julve and Francisco Lloret, a Friendly Pair of Two Exceptional Coordination Chemists in Molecular Magnetism

by Michel Verdaguer

Magnetochemistry 2025, 11(2), 6; https://doi.org/10.3390/magnetochemistry11020006 - 21 Jan 2025

Abstract

This laudatio is dedicated to Professors Miguel Julve Olcina and Francisco Lloret Pastor on the occasion of their retirement in 2024. The first part deals with the scientific trajectory of the Coordination Chemistry team at the University of Valencia, within the Department of [...] Read more.

This laudatio is dedicated to Professors Miguel Julve Olcina and Francisco Lloret Pastor on the occasion of their retirement in 2024. The first part deals with the scientific trajectory of the Coordination Chemistry team at the University of Valencia, within the Department of Inorganic Chemistry on the Burjassot campus and then in the Paterna Institute of Molecular Science. The second part relates some of the more salient results of the heritage left by our two colleagues in molecular magnetism, where they developed, in their own way, a rational approach to designing, creating and understanding a wealth of brand new systems from the simplest to Multifunctional Molecule-based Magnetic Materials. The robust and friendly links between our two colleagues are emphasized in the third part. 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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23 pages, 3584 KiB

Open AccessReview

Recent Advances of Colossal Magnetoresistance in Versatile La-Ca-Mn-O Material-Based Films

by Navjyoti Boora, Rafiq Ahmad, Shafaque Rahman, Nguyen Quoc Dung, Akil Ahmad, Mohammed B. Alshammari and Byeong-Il Lee

Magnetochemistry 2025, 11(1), 5; https://doi.org/10.3390/magnetochemistry11010005 - 16 Jan 2025

Abstract

Hole-doped manganese oxides exhibit a gigantic negative magnetoresistance, referred to as colossal magnetoresistance (CMR), owing to the interplay between double-exchange (DE) ferromagnetic metal and charge-ordered antiferromagnetic insulator/semiconductor phases. Magnetoresistive manganites display a sharp resistivity drop at the metal–insulator transition temperature (T^MI). [...] Read more.

Hole-doped manganese oxides exhibit a gigantic negative magnetoresistance, referred to as colossal magnetoresistance (CMR), owing to the interplay between double-exchange (DE) ferromagnetic metal and charge-ordered antiferromagnetic insulator/semiconductor phases. Magnetoresistive manganites display a sharp resistivity drop at the metal–insulator transition temperature (T^MI). CMR effects in perovskite manganites, specifically La_0.67Ca_0.33MnO₃ (La-Ca-Mn-O or LCMO), have been extensively investigated. This review paper provides a comprehensive introduction to the crystallographic structure, as well as the electronic and magnetic properties, of LCMO films. Furthermore, we delve into a detailed discussion of the effects of epitaxial strain induced by different substrates on LCMO films. Additionally, we review the early findings and diverse applications of LCMO thin films. Finally, we outline potential challenges and prospects for achieving superior LCMO film properties. Full article

(This article belongs to the Special Issue Magnetic Materials, Thin Films and Nanostructures—2nd Edition)

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15 pages, 3973 KiB

Open AccessArticle

Exploring the Potential of Oxalyldihydrazide-Derived Schiff Bases as Versatile Ligands: Synthesis, Structural Characterization, and Magnetic Properties

by Ernesto Costa-Villén, Marina Ortiz, Pedro Sitjar, Cristina Puigjaner and Mohamed Salah El Fallah

Magnetochemistry 2025, 11(1), 4; https://doi.org/10.3390/magnetochemistry11010004 - 13 Jan 2025

Abstract

Schiff bases constitute a broad and well-established class of ligands widely utilized in coordination chemistry. To further enrich this family and assess the potential impact of oxalyldihydrazide-derived Schiff bases in the realms of coordination chemistry and molecular magnetism, three novel ligands have been [...] Read more.

Schiff bases constitute a broad and well-established class of ligands widely utilized in coordination chemistry. To further enrich this family and assess the potential impact of oxalyldihydrazide-derived Schiff bases in the realms of coordination chemistry and molecular magnetism, three novel ligands have been synthesized and investigated. i.e., N′1,N′2-bis((E)-pyridin-2-ylmethylene)oxalohydrazide (H₂L1), N′1-((E)-(3-methylpyridin-2-yl)methylene)-N′2-((E)-(6-methylpyridin-2-yl)methylene)oxalohydrazide (H₂L2) and N′1,N′2-bis((E)-phenyl(pyridin-2-yl)methylene)oxalohydrazide (H₂L3) were synthesized and then combined with various 3d metals, resulting in the formation of five new complexes with formula [Cu₅(L1)₂(H₂O)₈(MeOH)₂(NO₃)₂](NO₃)₄ (1), [Mn₂(HL2)₂(BzO)₂(MeOH)₂]·2MeOH (2), [Ni(HL2)₂]·2MeOH (3), [Ni₄(L2)₄]·4MeOH (4), [Ni₈(L3)₄(AcO)₄(H₂O)₁₂](OAc)₄ (5). These compounds were structurally and magnetically characterized, revealing the various coordination modes exhibited by the ligands and a distinct antiferromagnetic behavior. Alternating current (AC) susceptibility measurements were conducted on complex 1, showing no evidence of Single Molecule Magnet (SMM) behavior. Full article

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

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13 pages, 2867 KiB

Open AccessArticle

Theoretical Study of Pentacoordinated Lanthanide Single-Ion Magnets via Ab Initio Electronic Structure Calculation

by Yu-Xi Wang, Yu-Fei Wang and Bing Yin

Magnetochemistry 2025, 11(1), 3; https://doi.org/10.3390/magnetochemistry11010003 - 7 Jan 2025

Abstract

A theoretical study, based on ab initio electronic structure calculation, is performed in a group of 16 pentacoordinate Dy-SIMs. Theoretical results provide a reasonable explanation of the observed SMM performance based on a concise criterion, i.e., the co-existence of long τ_QTM and [...] Read more.

A theoretical study, based on ab initio electronic structure calculation, is performed in a group of 16 pentacoordinate Dy-SIMs. Theoretical results provide a reasonable explanation of the observed SMM performance based on a concise criterion, i.e., the co-existence of long τ_QTM and high U_eff. To have the desired electronic structure favoring good SMM performance, the contribution from the equatorial coordinating atoms might be even more important than that from the axial coordinating atoms. Widening the axial ∠O–Dy–O might be a probable way to improve the SMM performance of pentacoordinated Dy-SIMs. Starting from existing systems, a rigid-scan type exploration indicates the possibility of U_eff higher than 1600 K. 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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13 pages, 4139 KiB

Open AccessArticle

Microstructural, Morphological, and Magnetic Effects of NiFe₂O₄ Shell Formation Around Nanospherical ZnFe₂O₄ Cores

by Marija Šuljagić, Vuk Uskoković, Lukasz Kilanski, Sabina Lewinska, Abdul Khaliq, Anna Ślawska-Waniewska, Aleksandar Kremenović, Vladimir Pavlović, Dejan A. Jeremić and Ljubica Andjelković

Magnetochemistry 2025, 11(1), 2; https://doi.org/10.3390/magnetochemistry11010002 - 5 Jan 2025

Abstract

First-row transition metal oxides have relatively modest magnetic properties compared to those of permanent magnets based on rare earth elements. However, there is a hope that this gap might be bridged via proper compositional and structural adjustments. Bi-magnetic nanostructures with homogeneous interfaces often [...] Read more.

First-row transition metal oxides have relatively modest magnetic properties compared to those of permanent magnets based on rare earth elements. However, there is a hope that this gap might be bridged via proper compositional and structural adjustments. Bi-magnetic nanostructures with homogeneous interfaces often exhibit a combination or synergy of properties of both phases, resulting in improved performance compared to their monophasic magnetic counterparts. To gain a deeper insight into these complex structures, a bi-magnetic nanostructured material composed of superparamagnetic nanoparticles comprising a zinc ferrite core and a nickel ferrite shell was synthesized using the seed-mediated growth approach. The resulting ZnFe₂O₄@NiFe₂O₄ core–shell nanoparticles were characterized using a series of experimental techniques and were compared to the ZnFe₂O₄ cores. Most importantly, the formation of the NiFe₂O₄ shell around the ZnFe₂O₄ core improved the net crystallinity of the material and altered the particle morphology by reducing the convexity of the surface. Simultaneously, the magnetic measurements demonstrated the coherence of the interface between the core and the shell. These effects combined led to improved spin coupling and stronger magnetism, as evidenced by higher saturation magnetization and the doubling of the blocking temperature for the ZnFe₂O₄@NiFe₂O₄ core–shell particles relative to the ZnFe₂O₄ cores. Full article

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14 pages, 2876 KiB

Open AccessArticle

Slow Relaxation of the Magnetisation in a Two-Dimensional Metal–Organic Framework with a Layered Square Lattice

by Samia Benmansour, Christian Cerezo-Navarrete and Carlos J. Gómez-García

Magnetochemistry 2025, 11(1), 1; https://doi.org/10.3390/magnetochemistry11010001 - 26 Dec 2024

Abstract

Herein, we present the synthesis and structural characterisation of two layered MOFs with the asymmetric ligand 3-chloro,6-cyano-2,5-dihydroxy-1,4-benzoquinone dianion (C₆O₄(CN)Cl²⁻ = chlorocyananilato). These compounds, formulated as (H₃O)[Eu(C₆O₄(CN)Cl)₂(H₂O)]·34H₂O [...] Read more.

Herein, we present the synthesis and structural characterisation of two layered MOFs with the asymmetric ligand 3-chloro,6-cyano-2,5-dihydroxy-1,4-benzoquinone dianion (C₆O₄(CN)Cl²⁻ = chlorocyananilato). These compounds, formulated as (H₃O)[Eu(C₆O₄(CN)Cl)₂(H₂O)]·34H₂O (1) and (H₃O)[Dy(C₆O₄(CN)Cl)₂(H₂O)]·44H₂O (2), are isostructural and show a (4,4)-layered square structure with the crystallisation water molecules located between the layers. The lanthanoid ions are surrounded by four bis-bidentate chlorocyananilato ligands that connect each Ln^III centre with other four, giving rise to square cavities formed by Ln^III centres in the vertices and chlorocyananilato ligands as the sides. There is an additional coordinated water molecule that occupies the caped position of the capped square antiprismatic coordination geometry around the Ln^III centres. The magnetic properties show the presence of a field-induced slow relaxation of the magnetisation in the Dy^III derivative at low temperatures that follows Direct and Orbach relaxation mechanisms with an energy barrier of 36(3) K. 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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19 pages, 11321 KiB

Open AccessArticle

Uncovering the Mechanisms of Long-Range Magnetic Order in [Mn(mal)(H₂O)]_n: Insights from Microscopic and Macroscopic Magnetic Analysis

by Fernando S. Delgado, Laura Cañadillas-Delgado, Juan Rodríguez-Carvajal, Óscar Fabelo and Jorge Pasán

Magnetochemistry 2024, 10(12), 109; https://doi.org/10.3390/magnetochemistry10120109 - 20 Dec 2024

Abstract

In this study, we investigate the magnetic properties of the molecular compound [Mn(mal)(H₂O)]ₙ (mal = dianion of malonic acid) by integrating microscopic and macroscopic characterization, combining unpolarized neutron diffraction and magnetometry measurements. Neutron diffraction, though non-commonly applied to molecular compounds, proved [...] Read more.

In this study, we investigate the magnetic properties of the molecular compound [Mn(mal)(H₂O)]ₙ (mal = dianion of malonic acid) by integrating microscopic and macroscopic characterization, combining unpolarized neutron diffraction and magnetometry measurements. Neutron diffraction, though non-commonly applied to molecular compounds, proved essential for fully resolving the magnetic structure, as well as overcoming challenges such as hydrogen-related incoherent scattering and difficulties in accurately locating light atoms. Our neutron data provided critical structural details, including the precise location of hydrogen atoms, especially those associated with crystallization water molecules. By conducting low-temperature measurements below the magnetic ordering temperature, we identified the correct Shubnikov space group (Pc’a2₁’) and established a magnetic model consistent with the observed weak ferromagnetism. Our findings reveal that the compound presents a spin-canted structure with a weak ferromagnetic signal along the b-axis. This signal originates primarily from antisymmetric exchange interactions rather than single-ion anisotropy, consistent with the isotropic nature of the Mn(II) (⁶A₁g) ground state. The combined neutron diffraction and magnetometry results provide a comprehensive understanding of how structural and symmetry factors influence the magnetic properties of malonate-based manganese compounds. 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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4 pages, 175 KiB

Open AccessEditorial

Advances in Magnetic Nanomaterials and Nanostructures

by Francesco Congiu and Giorgio Concas

Magnetochemistry 2024, 10(12), 108; https://doi.org/10.3390/magnetochemistry10120108 - 18 Dec 2024

Abstract

Magnetic nanomaterials, in which non-bulk magnetic properties emerge because of their low dimension, are a class of materials with huge application potential in several areas, providing, at the same time, an exciting field of fundamental research [...] Full article

(This article belongs to the Special Issue Advances in Magnetic Nanomaterials and Nanostructures)

31 pages, 11954 KiB

Open AccessReview

Exploring Spin-Crossover Cobalt(II) Single-Ion Magnets as Multifunctional and Multiresponsive Magnetic Devices: Advancements and Prospects in Molecular Spintronics and Quantum Computing Technologies

by Renato Rabelo, Luminita M. Toma, Abdeslem Bentama, Salah-Eddine Stiriba, Rafael Ruiz-García and Joan Cano

Magnetochemistry 2024, 10(12), 107; https://doi.org/10.3390/magnetochemistry10120107 - 17 Dec 2024

Abstract

Spin-crossover (SCO) and single-ion magnets (SIMs), or their mixed SCO-SIM derivatives, are a convenient solution in the evolution from molecular magnetism toward molecular spintronics and quantum computing. Herein, we report on the current trends and future directions on the use of mononuclear six-coordinate [...] Read more.

Spin-crossover (SCO) and single-ion magnets (SIMs), or their mixed SCO-SIM derivatives, are a convenient solution in the evolution from molecular magnetism toward molecular spintronics and quantum computing. Herein, we report on the current trends and future directions on the use of mononuclear six-coordinate Co^II SCO-SIM complexes with potential opto-, electro-, or chemo-active 2,6-pyridinediimine (PDI)- and 2,2′:6′,2′-terpyridine (TERPY)-type ligands as archetypical examples of multifunctional and multiresponsive magnetic devices for applications in molecular spintronics and quantum computing technologies. This unique class of spin-crossover cobalt(II) molecular nanomagnets is particularly well suited for addressing and scaling on different supports, like metal molecular junctions or carbon nanomaterials (CNMs) and metal–organic frameworks (MOFs) or metal-covalent organic frameworks (MCOFs), in order to measure the single-molecule electron transport and quantum coherence properties, which are two major challenges in single-molecule spintronics (SMS) and quantum information processing (QIP). 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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8 pages, 2806 KiB

Open AccessArticle

Observation of Zigzag-Shaped Magnetic Domain Boundaries in Granular Perpendicular Magnetic Recording Media Using Alternating Magnetic Force Microscopy

by M. V. Makarova, Hanamichi Tanaka, Hiroshi Sonobe, Toru Matsumura and Hitoshi Saito

Magnetochemistry 2024, 10(12), 106; https://doi.org/10.3390/magnetochemistry10120106 - 13 Dec 2024

Abstract

In granular media for perpendicular magnetic recording, zigzag-shaped magnetic domain boundaries form between magnetic grains isolated by a non-magnetic grain boundary phase. They are the main source of jitter noise caused by the position fluctuation of magnetic bit transitions. The imaging of zigzag [...] Read more.

In granular media for perpendicular magnetic recording, zigzag-shaped magnetic domain boundaries form between magnetic grains isolated by a non-magnetic grain boundary phase. They are the main source of jitter noise caused by the position fluctuation of magnetic bit transitions. The imaging of zigzag boundaries thus becomes an important task to increase recording density with decreasing bit size, when the zigzag and bit sizes become comparable. We visualized the zigzag boundaries of magnetic domains in as-sputtered granular media with a spatial resolution of less than 3 nm using our developed Alternating Magnetic Force Microscopy (A-MFM). We used a soft magnetic amorphous FeCoB tip with high saturation magnetization, which further enhances the spatial resolution through the inverse magnetostrictive effect. The zigzag size ranged from 2 to 8 nm in media with an estimated grain size of around 5 nm. Additionally, we observed zigzag bit boundaries in commercially recorded granular media with a recording density of 500 kfci. Full article

(This article belongs to the Section Magnetic Nanospecies)

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16 pages, 7565 KiB

Open AccessArticle

Preparation of the New Magnetic Nanoadsorbent Fe₃O₄@SiO₂-yl-VP and Study on the Adsorption Properties of Hg (II) and Pb (II) in Water

by Dun Chen, Jianxin Chen, Wanyong Zhou and Amatjan Sawut

Magnetochemistry 2024, 10(12), 105; https://doi.org/10.3390/magnetochemistry10120105 - 13 Dec 2024

Abstract

This article reports the preparation of a novel functionalized magnetic nanoadsorbent through an addition reaction between Fe₃O₄ nanoparticles coated with allyl silica gel and 4-pyridinyl ethylene. A detailed characterization of Fe₃O₄@SiO₂-yl-VP was conducted. Among [...] Read more.

This article reports the preparation of a novel functionalized magnetic nanoadsorbent through an addition reaction between Fe₃O₄ nanoparticles coated with allyl silica gel and 4-pyridinyl ethylene. A detailed characterization of Fe₃O₄@SiO₂-yl-VP was conducted. Among them, in the infrared spectrum, we can easily see that the absorption peak of the C=C stretching vibration at 1660 cm⁻¹ in the raw material disappears after the addition reaction, indicating the successful grafting of polymer on the surface of silica gel. The appearance of N element in the EDS spectrum also proves the successful completion of the addition reaction and the successful synthesis of Fe₃O₄@SiO₂-yl-VP. At pH = 5 and pH = 7, it only takes half an hour for Fe₃O₄@SiO₂-yl-VP to achieve maximum adsorption capacities of 85.06 and 73.78 mg/g for Hg (II) and Pb (II), respectively. The adsorption process conforms to the Langmuir model and the pseudo-first- and pseudo-second-order kinetic models and can be reused 11 times, demonstrating excellent reusability. Full article

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

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18 pages, 2865 KiB

Open AccessArticle

Engineering Mononuclear Ln(III) Complexes with a Pseudo-Macrocyclic Hexadentate N₄O₂ Schiff Base Ligand Exhibiting Slow Magnetic Relaxation

by Ismael Francisco Diaz-Ortega, Yating Ye, Jesus Jover, Eliseo Ruiz, Enrique Colacio and Juan Manuel Herrera

Magnetochemistry 2024, 10(12), 104; https://doi.org/10.3390/magnetochemistry10120104 - 12 Dec 2024

Abstract

We report here the synthesis of a series of nine coordinated mononuclear Ln^III complexes [LnL₁Cl₂(DMF)]Cl·2.5DMF and [LnL¹(L₂)₂]Cl·4CH₃OH (Ln^III = Gd^III, Dy^III, Er^III and Yb [...] Read more.

We report here the synthesis of a series of nine coordinated mononuclear Ln^III complexes [LnL₁Cl₂(DMF)]Cl·2.5DMF and [LnL¹(L₂)₂]Cl·4CH₃OH (Ln^III = Gd^III, Dy^III, Er^III and Yb^III, HL₂ = 9-anthracenecarboxylic acid), where L1 is a hexadentate N₄O₂ Schiff base ligand prepared from the condensation of 1,10-phenanthroline-2,9-dicarbaldehyde and semicarbazone. The X-ray crystal structures of these complexes show the Ln^III ions to possess LnN₄O₂Cl₂ and LnN₄O₄ coordination spheres, which can be considered to be derived from a hexagonal bipyramidal geometry, with the ligand in the equatorial plane and the anions (chloride or 9-antracenecarboxylate) in axial positions, which undergo distortion after coordination of either a molecule of DMF or a bidentate coordination of the 9-anthracenecarboxxylate ligand. All these compounds exhibit field-induced slow magnetization relaxation (SMR). The absence of SMR at zero field due to QTM, as well as the processes involved in the magnetic relaxation under a field of 0.1 T, have been justified on the basis of theoretical calculations and the distortion of the respective coordination spheres. The severe discrepancy between the calculated and experimental thermal energy barriers for the Dy^III complexes seems to indicate that the relaxation occurs with the contribution of spin–vibrational coupling, which is favored by the flexibility of the ligand. 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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20 pages, 6567 KiB

Open AccessArticle

Calixarene-like Lanthanide Single-Ion Magnets Based on Nd^III, Gd^III, Tb^III and Dy^III Oxamato Complexes

by Tamyris T. da Cunha, João Honorato de Araujo-Neto, Meiry E. Alvarenga, Felipe Terra Martins, Emerson F. Pedroso, Davor L. Mariano, Wallace C. Nunes, Nicolás Moliner, Francesc Lloret, Miguel Julve and Cynthia L. M. Pereira

Magnetochemistry 2024, 10(12), 103; https://doi.org/10.3390/magnetochemistry10120103 - 12 Dec 2024

Abstract

In this work, we describe the synthesis, crystal structures and magnetic properties of four air-stable mononuclear lanthanide(III) complexes with the N-(2,4,6-trimethylphenyl)oxamate (Htmpa) of formula: n-Bu₄N[Nd(Htmpa)₄(H₂O)]·4H₂O (1), n-Bu₄N[Gd(Htmpa)₄ [...] Read more.

In this work, we describe the synthesis, crystal structures and magnetic properties of four air-stable mononuclear lanthanide(III) complexes with the N-(2,4,6-trimethylphenyl)oxamate (Htmpa) of formula: n-Bu₄N[Nd(Htmpa)₄(H₂O)]·4H₂O (1), n-Bu₄N[Gd(Htmpa)₄(H₂O)]·3DMSO·2H₂O (2), n-Bu₄N[Tb(Htmpa)₄(H₂O)]·3DMSO·1H₂O (3) and n-Bu₄N[Dy(Htmpa)₄(H₂O)]·3DMSO·2H₂O (4) (n-Bu₄N⁺ = n-tetrabutylammonium; DMSO = dimethylsulfoxide). Their crystal structures reveal the occurrence of calixarene-type monoanionic species containing all-cis-disposed Htmpa ligands and one water molecule coordinated with the respective Ln^III ion (Ln = Nd, Gd, Tb and Dy), featuring a nine-coordinated environment with muffin (MFF-9) (1) or spherical-capped square antiprism (CSAPR-9) (2–4) geometry. The major difference between their crystal structures is related to the nature of crystallization solvent molecules, either water (1) or both DMSO and water (2–4). The intermolecular hydrogen bonds among the self-complementary Htmpa ligands in all four compounds mediated a 2 D supramolecular network in the solid state. Direct-current (dc) magnetic properties for 1–4 show typical behavior for the ground state terms of the Ln^III ions [⁴I_9/2 (Nd); ⁸S_7/2(Gd), ⁷F₆ (Tb), ⁶H^15/2 (Dy)]. Alternating-current (ac) magnetic measurements reveal the presence of slow magnetic relaxation without the presence of a dc field only for 4. In contrast, field-induced slow magnetic relaxation behavior was found in complexes 1, 2 and 3. Full article

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

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13 pages, 5237 KiB

Open AccessArticle

A Trinuclear Co(II) Complex Based on the Tris-Dioxolene Triphenylene Non-Innocent Bridge: Complementary Redox, Magnetic Behavior and Theoretical Calculations

by Aristide Colin, Yiting Wang, François Lambert, Nathalie Bridonneau, Nicolas Suaud, Régis Guillot, Eric Rivière, Zakaria Halime, Nathalie Guihéry, Shin-ichi Ohkoshi and Talal Mallah

Magnetochemistry 2024, 10(12), 102; https://doi.org/10.3390/magnetochemistry10120102 - 11 Dec 2024

Abstract

A trinuclear Co(II)-containing complex was assembled using the non-innocent hexahydroxytriphenylene bridging ligand. Cyclovoltammetry and spectroelectrochemistry studies revealed that the central ligand sustained four reversible redox events, leading to different species with diverse optical behavior. Complementary analysis of the molecular structure confirmed by ab [...] Read more.

A trinuclear Co(II)-containing complex was assembled using the non-innocent hexahydroxytriphenylene bridging ligand. Cyclovoltammetry and spectroelectrochemistry studies revealed that the central ligand sustained four reversible redox events, leading to different species with diverse optical behavior. Complementary analysis of the molecular structure confirmed by ab initio theoretical calculations were consistent with the bridge in the tris-semiquinone (sq) state for the trinuclear complex. The exchange coupling among the electrons of the bridge resulted in a spin doublet (s = ½) localized close to one of the three Co²⁺ ions, as suggested by the experimental magnetic data. The central doublet underwent one large antiferromagnetic exchange coupling with one Co(II) and almost no coupling with the two other metal ions. Full article

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

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12 pages, 6474 KiB

Open AccessArticle

A Novel Magnetic Flux Leakage Method Incorporating TMR Sensors for Detecting Zinc Dross Defects on the Surface of Hot-Dip Galvanized Sheets

by Bo Wang, San Zhang, Jie Wang, Liqin Jing and Feilong Mao

Magnetochemistry 2024, 10(12), 101; https://doi.org/10.3390/magnetochemistry10120101 - 10 Dec 2024

Abstract

Surface quality control of hot-dip galvanized sheets is a critical research topic in the metallurgical industry. Zinc dross, the most common surface defect in the hot-dip galvanizing process, significantly affects the sheet’s service performance. In this manuscript, a novel magnetic flux leakage (MFL) [...] Read more.

Surface quality control of hot-dip galvanized sheets is a critical research topic in the metallurgical industry. Zinc dross, the most common surface defect in the hot-dip galvanizing process, significantly affects the sheet’s service performance. In this manuscript, a novel magnetic flux leakage (MFL) detection method was proposed to detect zinc dross defects on the surface of hot-dip galvanized steel sheets. Instead of using exciting coils in traditional methods, a tiny permanent magnet with a millimeter magnitude was employed to reduce the size and weight of the equipment. Additionally, a high-precision tunnel magnetoresistance (TMR) sensor with a sensitivity of 300 mV/V/Oe was selected to achieve higher detection accuracy. The experimental setup was established, and the x-axis direction (sample movement direction) was determined as the best measurement axis by vector analysis through experiments and numerical simulation. The detection results indicate that this novel MFL detection method could detect industrial zinc dross with an equivalent size of 400 μm, with high signal repeatability and signal-to-noise ratio. In the range of 0–1200 mm/s, the detection speed has almost no effect on the measurement signal, which indicates that this novel method has higher adaptability to various conditions. The multi-path scanning method with a single probe was used to simulate the array measurement to detect a rectangular area of 30 × 60 mm. Ten zinc dross defects were detected across eight measurement paths with 4 mm intervals, and the positions of these zinc dross defects were successfully reconstructed. The research results indicate that this novel MFL detection method is simple and feasible. Furthermore, the implementation of array measurements provides valuable guidance for subsequent in-depth research and potential industrial applications in the future. Full article

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

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3 pages, 171 KiB

Open AccessEditorial

Advances in Magnetic Two Dimensional Materials

by Xiaoxi Li and Bo Li

Magnetochemistry 2024, 10(12), 100; https://doi.org/10.3390/magnetochemistry10120100 - 9 Dec 2024

Abstract

Since the discovery of graphene in 2004, two-dimensional (2D) van der Waals (vdW) layered materials have attracted extensive attention for their great potential for application in the electronic, optoelectronic, and electrochemical fields [...] Full article

(This article belongs to the Special Issue Advances in Magnetic Two Dimensional Materials)

12 pages, 3251 KiB

Open AccessArticle

Controlled Zn(II) to Co(II) Transmetalation in a Metal–Organic Framework Inducing Single-Ion Magnet Behavior

by Paula Escamilla, Nicolás Moliner, Donatella Armentano, Emilio Pardo, Jesús Ferrando-Soria and Thais Grancha

Magnetochemistry 2024, 10(12), 99; https://doi.org/10.3390/magnetochemistry10120099 - 6 Dec 2024

Abstract

The intrinsic characteristic features of metal–organic frameworks offer unique, great opportunities to develop novel materials with applications in very diverse fields. Aiming to take advantage of these, the application of post-synthetic methodologies has revealed itself to be a powerful approach to the isolation [...] Read more.

The intrinsic characteristic features of metal–organic frameworks offer unique, great opportunities to develop novel materials with applications in very diverse fields. Aiming to take advantage of these, the application of post-synthetic methodologies has revealed itself to be a powerful approach to the isolation and structuration of metal ions, molecules, or more complex species, either within MOF channels or reticulated at their network, rendering novel and exciting MOFs with new or improved functionalities. Herein, we report the partial post-synthetic metal exchange of Zn(II) metal ions by Co(II) ones in water-stable three-dimensional CaZn₆-MOF 1, derived from the amino acid S-methyl-L-cysteine, allowing us to obtain two novel MOFs with increasing contents of the Co(II) ions Co_4%@1 and Co_8%@1. Remarkably, the presented post-synthetic metal exchange methodology has two relevant implications for us: (i) it allowed us to obtain two novel MOFs, which were not accessible by direct synthesis, and (ii) enabled us to transform physical properties within this family of isoreticular MOFs from the diamagnetic pristine MOF 1 to MOFs Co_4%@1 and Co_8%@1, exhibiting field-induced, frequency-dependent, alternating current magnetic susceptibility signals, which are characteristic features of single-molecule magnets. 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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