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Magnetochemistry, Volume 9, Issue 11 (November 2023) – 9 articles

Cover Story (view full-size image): The involvement of spin symmetry in the evaluation of zero-field energy levels in polynuclear transition metal and lanthanide complexes facilitates the division of the large-scale Hamiltonian matrix referring to isotropic exchange. This method is based on the use of an irreducible tensor approach. This allows for the fitting of the experimental data of magnetic susceptibility and magnetization in a reasonable time for relatively large clusters for any coupling path. Several examples represented by catena-[AN} and cyclo-[AN] systems were modeled. View this paper
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9 pages, 2640 KiB  
Communication
Dzyaloshinsky–Moriya Interaction Induced Anomalous g Behavior of Sr2IrO4 Probed by Electron Spin Resonance
Magnetochemistry 2023, 9(11), 231; https://doi.org/10.3390/magnetochemistry9110231 - 19 Nov 2023
Viewed by 1131
Abstract
Among the 5d transition metal iridates, Sr2IrO4, which has a layered chalcogenide structure, has received much attention due to its strong spin–orbit coupling (SOC), which produces Mott insulating states and anomalous physical behaviors. In this paper, the microscopic magnetism [...] Read more.
Among the 5d transition metal iridates, Sr2IrO4, which has a layered chalcogenide structure, has received much attention due to its strong spin–orbit coupling (SOC), which produces Mott insulating states and anomalous physical behaviors. In this paper, the microscopic magnetism of Sr2IrO4 is studied with electron spin resonance (ESR) measurements. The Lande factor g of the ferromagnetic resonance signal of Sr2IrO4 shows anomalous behavior compared to typical ferromagnets. It gradually decreases, and the corresponding resonance field Hr increases, with decreasing temperature. The various physical parameters. including the saturated magnetic field Hs derived from M-H, Hr, ΔHpp, the g factor and the intensity I extracted from ESR spectra, are analyzed in detail. Eventually, it is revealed that the anomalous behavior of the g-factor is induced by in-plane Dzyaloshinsky–Moriya interaction (DMI) rather than the SOC effect. Full article
(This article belongs to the Section Spin Crossover and Spintronics)
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16 pages, 2139 KiB  
Article
Exploring Crystal Structure, Hyperfine Parameters, and Magnetocaloric Effect in Iron-Rich Intermetallic Alloy with ThMn12-Type Structure: A Comprehensive Investigation Using Experimental and DFT Calculation
Magnetochemistry 2023, 9(11), 230; https://doi.org/10.3390/magnetochemistry9110230 - 18 Nov 2023
Viewed by 1339
Abstract
In this study, we give a thorough evaluation of the structural, magnetic, and magnetocaloric properties in iron-rich PrFe11Ti intermetallic alloy with ThMn12-type structure using a combination of experimental and theoretical analysis. X-ray diffraction coupled with Rietveld refinement was used [...] Read more.
In this study, we give a thorough evaluation of the structural, magnetic, and magnetocaloric properties in iron-rich PrFe11Ti intermetallic alloy with ThMn12-type structure using a combination of experimental and theoretical analysis. X-ray diffraction coupled with Rietveld refinement was used to characterize the structure, which revealed a unique tetragonal crystal structure with I4/mmm space group. The 8i site was identified as the preferred site for the Ti atom. This finding was confirmed by various techniques, including XRD, DFT, and Mössbauer spectrometry. Magnetic properties were studied through intrinsic magnetic measurements and magnetocaloric effect analysis. Mössbauer spectroscopy was employed to probe the local magnetic environment and for further characterization of the material’s magnetic properties. The experimental results were complemented by theoretical calculations based on density functional theory (DFT). A promising magnetocaloric effect is observed, with a significant maximum magnetic entropy (ΔSMmax = 2.5 J·kg1·K1) and a relative cooling power about 70 J·kg1 under low magnetic field change μ0ΔH = 1.5 T. Overall, our results provide a deeper understanding of the structural and magnetic properties of the material under study and demonstrate the effectiveness of the combined experimental and theoretical approach in the investigation of complex materials. The insights gained from this study could have implications for the development of advanced magnetic materials with enhanced properties for potential magnetic applications. Full article
(This article belongs to the Section Magnetic Materials)
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14 pages, 9030 KiB  
Article
Honey-like Odor Meets Single-Ion Magnet: Synthesis, Crystal Structure, and Magnetism of Cobalt(II) Complex with Aromatic Trans-Cinnamic Acid
Magnetochemistry 2023, 9(11), 229; https://doi.org/10.3390/magnetochemistry9110229 - 16 Nov 2023
Viewed by 1124
Abstract
The hexacoordinate Co(II) complex [Co(neo)2(cin)][BPh4]·½Me2CO (1·½Me2CO) containing trans-cinnamic acid (Hcin) and neocuproine (neo) was prepared. The compound 1·½Me2CO was characterized via single-crystal X-ray analysis, FT-IR spectroscopy, and magnetic measurements. [...] Read more.
The hexacoordinate Co(II) complex [Co(neo)2(cin)][BPh4]·½Me2CO (1·½Me2CO) containing trans-cinnamic acid (Hcin) and neocuproine (neo) was prepared. The compound 1·½Me2CO was characterized via single-crystal X-ray analysis, FT-IR spectroscopy, and magnetic measurements. The coordination polyhedron of the complex cation adopts a deformed octahedron shape, and cinnamate exhibits a bidentate mode of coordination, which is unusual for mononuclear Co(II) cinnamate complexes. The analysis of DC magnetic measurements with zero-field splitting (ZFS) spin Hamiltonian revealed large magnetic anisotropy defined by the axial ZFS parameter D = +53.2 cm−1. AC susceptibility measurements revealed the slow relaxation of magnetization under the applied field; thus, 1·½Me2CO behaves as a field-induced single-molecule magnet. The analysis of magnetic properties was also supported by CASSCF/NEVPT2 calculations. Full article
(This article belongs to the Section Molecular Magnetism)
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14 pages, 11436 KiB  
Article
Synthesis and Characterization of Hematite, Magnetite and Maghemite Supported on Silica Gel
Magnetochemistry 2023, 9(11), 228; https://doi.org/10.3390/magnetochemistry9110228 - 15 Nov 2023
Viewed by 1098
Abstract
A new method for obtaining nanosized particles of iron oxides using porous silica gel is proposed. In situ magnetometry was used to study the reduction of hematite deposited on silica gel during the thermolysis of glucose. The formed magnetite and maghemite obtained by [...] Read more.
A new method for obtaining nanosized particles of iron oxides using porous silica gel is proposed. In situ magnetometry was used to study the reduction of hematite deposited on silica gel during the thermolysis of glucose. The formed magnetite and maghemite obtained by subsequent oxidation of the magnetite were studied using X-ray diffraction and Mossbauer spectroscopy. It was shown that both the size of the oxide particles and the phase composition significantly depended on the porous structure of the silica gel. In particular, the formation of superparamagnetic maghemite particles on silica gels with pore sizes of 30, 15 and 10 nm was demonstrated. Full article
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13 pages, 3650 KiB  
Article
Electrophoretic Deposition of One- and Two-Layer Compacts of Holmium and Yttrium Oxide Nanopowders for Magneto-Optical Ceramics Fabrication
Magnetochemistry 2023, 9(11), 227; https://doi.org/10.3390/magnetochemistry9110227 - 15 Nov 2023
Viewed by 947
Abstract
In this work, the possibility of fabricating composite magneto-optical ceramics by electrophoretic deposition (EPD) of nanopowders and high-temperature vacuum sintering of the compacts was investigated. Holmium oxide was chosen as a magneto-optical material for the study because of its transparency in the mid-IR [...] Read more.
In this work, the possibility of fabricating composite magneto-optical ceramics by electrophoretic deposition (EPD) of nanopowders and high-temperature vacuum sintering of the compacts was investigated. Holmium oxide was chosen as a magneto-optical material for the study because of its transparency in the mid-IR range. Nanopowders of magneto-optical (Ho0.95La0.05)2O3 (HoLa) material were made by self-propagating high-temperature synthesis. Nanopowders of (Y0.9La0.1)2O3 (YLa) were made by laser synthesis for an inactive matrix. The process of formation of one- and two-layer compacts by EPD of the nanopowders from alcohol suspensions was studied in detail. Acetylacetone was shown to be a good dispersant to obtain alcohol suspensions of the nanopowders, characterized by high zeta potential values (+29–+80 mV), and to carry out a stable EPD process. One-layer compacts were made from the HoLa and YLa nanopowders with a density of 30–43%. It was found out that the introduction of polyvinyl butyral (PVB) into the suspension leads to a decrease in the mass and thickness of the green bodies deposited, but does not significantly affect their density. The possibility of making two-layer (YLa/HoLa) compacts with a thickness of up to 2.6 mm and a density of up to 46% was demonstrated. Sintering such compacts in a vacuum at a temperature of 1750 °C for 10 h leads to the formation of ceramics with a homogeneous boundary between the YLa/HoLa layers and a thickness of the interdiffused ion layer of about 30 μm. Full article
(This article belongs to the Special Issue New Trends in Magneto-Optical Ceramics)
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50 pages, 40339 KiB  
Review
Spin Symmetry in Polynuclear Exchange-Coupled Clusters
Magnetochemistry 2023, 9(11), 226; https://doi.org/10.3390/magnetochemistry9110226 - 06 Nov 2023
Viewed by 1125
Abstract
The involvement of spin symmetry in the evaluation of zero-field energy levels in polynuclear transition metal and lanthanide complexes facilitates the division of the large-scale Hamiltonian matrix referring to isotropic exchange. This method is based on the use of an irreducible tensor approach. [...] Read more.
The involvement of spin symmetry in the evaluation of zero-field energy levels in polynuclear transition metal and lanthanide complexes facilitates the division of the large-scale Hamiltonian matrix referring to isotropic exchange. This method is based on the use of an irreducible tensor approach. This allows for the fitting of the experimental data of magnetic susceptibility and magnetization in a reasonable time for relatively large clusters for any coupling path. Several examples represented by catena-[AN} and cyclo-[AN] systems were modeled. Magnetic data for 20 actually existing endohedral clusters were analyzed and interpreted. Full article
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13 pages, 19000 KiB  
Article
Novel Tetranuclear Heterometallic Mn3Ni and Mononuclear Ni Complexes with an ONO Schiff Base Ligand: Synthesis, Crystal Structures, and Magnetic Properties
Magnetochemistry 2023, 9(11), 225; https://doi.org/10.3390/magnetochemistry9110225 - 03 Nov 2023
Viewed by 886
Abstract
A mononuclear Ni(II) complex, [Ni(HL1)2], (1) and a novel tetranuclear heterometal Mn-Ni complex, [Mn3Ni(L1)4Cl2(EtOH)2], (2) [H2L1 = N-(2-hydroxymethylphenyl)salicylideneimine], have been synthesized and characterized via X-ray crystal [...] Read more.
A mononuclear Ni(II) complex, [Ni(HL1)2], (1) and a novel tetranuclear heterometal Mn-Ni complex, [Mn3Ni(L1)4Cl2(EtOH)2], (2) [H2L1 = N-(2-hydroxymethylphenyl)salicylideneimine], have been synthesized and characterized via X-ray crystal structure analyses, infrared spectra, and elemental analyses. The structure analyses revealed that the tridentate ligand, H2L1, coordinates in a facial mode for Ni and a mer mode for Mn, respectively. Complex 2 includes Mn(II)Mn(III)2Ni(II) tetranuclear metal core bridged by μ-phenoxo and μ-alkoxo oxygens. Magnetic measurements for 2 indicate that weak ferromagnetic interactions (JMn(III)Ni(II) = 2.23, JMn(III)Mn(II) = 0.46, JMn(II)Ni(II) = 1.78, and JMn(III)Mn(III) = 0.58 cm−1) dominate in the tetranuclear core. Additionally, in alternating current (AC) magnetic measurements, frequency-dependent out-of-phase responses were observed. Full article
(This article belongs to the Section Molecular Magnetism)
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25 pages, 731 KiB  
Article
Jahn–Teller Magnets
Magnetochemistry 2023, 9(11), 224; https://doi.org/10.3390/magnetochemistry9110224 - 02 Nov 2023
Viewed by 1097
Abstract
A wide class of materials with different crystal and electronic structures including quasi-2D unconventional superconductors, such as cuprates, nickelates, ferropnictides/chalcogenides, ruthenate Sr2RuO4, and 3D systems, such as manganites RMnO3, ferrates (CaSr)FeO3, nickelates RNiO3, [...] Read more.
A wide class of materials with different crystal and electronic structures including quasi-2D unconventional superconductors, such as cuprates, nickelates, ferropnictides/chalcogenides, ruthenate Sr2RuO4, and 3D systems, such as manganites RMnO3, ferrates (CaSr)FeO3, nickelates RNiO3, silver oxide AgO, are based on Jahn–Teller 3d and 4d ions. These unusual materials, called Jahn–Teller (JT) magnets, are characterized by an extremely rich variety of phase states, spanning from non-magnetic and magnetic insulators to unusual metallic and superconducting states. The unconventional properties of JT magnets can be attributed to the instability of their highly symmetric Jahn–Teller “progenitors” with the ground orbital E-state with repect to charge transfer, anti-Jahn–Teller d-d disproportionation, and the formation of a system of effective local composite spin–singlet or spin–triplet, electronic, or hole S-type bosons moving in a non-magnetic or magnetic lattice. We consider specific features of the anti-JT-disproportionation reaction, properties of the electron–hole dimers, possible phase states and effective Hamiltonians for single- and two-band JT magnets, concluding with a short overview of physical properties for actual JT magnets. Full article
(This article belongs to the Section Magnetic Materials)
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14 pages, 2988 KiB  
Review
Variability of the Conductance Changes Associated with the Change in the Spin State in Molecular Spin Crossover Complexes
Magnetochemistry 2023, 9(11), 223; https://doi.org/10.3390/magnetochemistry9110223 - 29 Oct 2023
Viewed by 1113
Abstract
Here, we examine the conductance changes associated with the change in spin state in a variety of different structures, using the example of the spin crossover complex [Fe(H2B(pz)2)2(bipy)] (pz = (pyrazol-1-yl)-borate and bipy = 2,2′-bipyridine) and [Fe(Htrz) [...] Read more.
Here, we examine the conductance changes associated with the change in spin state in a variety of different structures, using the example of the spin crossover complex [Fe(H2B(pz)2)2(bipy)] (pz = (pyrazol-1-yl)-borate and bipy = 2,2′-bipyridine) and [Fe(Htrz)2(trz)](BF4)] (Htrz = 1H-1,2,4-triazole) thin films. This conductance change is highly variable depending on the mechanism driving the change in spin state, the substrate, and the device geometry. Simply stated, the choice of spin crossover complex used to build a device is not the only factor in determining the change in conductance with the change in spin state. Full article
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