Magnetic Susceptibility Measurements Research Articles

A new S = 2 kagomé lattice compound with ferromagnetic behaviors

A new compound NaMn3(SeO3)2(HSeO3)6 was obtained by a conventional hydrothermal method. This compound crystallizes in a trigonal system with space group R-3, exhibiting a typical kagomé structure, where the kagomé layers are composed of [MnO6] octahedra linked by [SeO3] groups. Magnetic susceptibility measurements confirm that this compound exhibits a ferromagnetic transition at ∼13 K, as further confirmed by the heat capacity data. The magnetic entropy was estimated, indicating that the system may release almost the entire entropy at low temperature.

Structure and magnetism of DyIII2 based triple-stranded helicates derived from dinucleating Schiff base ligands

We report herein the synthesis of three dinuclear DyIII helicates, [DyIII2(H2LR)3](NO3)3·xH2O (1–3, R = Me, Cl, Br), by reacting Dy(NO3)3·5H2O and three closely related Schiff bases derived from 3-Hydroxy-2-naphthohydrazide and three different 2,6-diformylphenols. Single crystal X-ray structural characterization revealed that all these complexes are isostructural and composed of complex cations of general formula [DyIII2(H2LR)3]3+, in which three monoanionic Schiff base ligands are wrapped around two DyIII centers, leading to triple-stranded helical structures. Notably, the configuration of monoanionic H2LR ligands imparts a coordination-induced chirality on individual complex cation, and the presence of equivalent amounts of enantiopure Λ and Δ complex cations made the solid products as racemic mixtures, crystalizing in the centrosymmetrical space groups. Variable-temperature magnetic susceptibility measurements have been performed in the temperature range 2 − 300 K for a representative complex 2, and AC susceptibility studies further disclose the slow relaxation of magnetization in 2, characteristics for single-molecule magnets.

The effect of the outer-sphere cations on the photophysical and magnetic properties of rare earth complexes with 2,2,2-trichloro-N-(diphenylphosphoryl)acetamide

Two series of rare earth coordination compounds have been synthesized (Na[RE(L4)] (labeled as 1RE) and PPh4[RE(L4)] (labeled as 2RE), where RE = Y3+, Eu3+, Tb3+, L = 2,2,2-trichloro-N-(diphenylphosphoryl)acetamide) to determine the possibility of modifying their photophysical and magnetical properties by changing the counterion. The crystal structure of 1RE was determined based on the single-crystal X-ray diffraction and the crystal structure of 2RE was determined based on quantum chemistry computational procedures. Characterization of the physicochemical properties of the compounds was carried out using differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), 1H and 31P NMR spectroscopy as well as FT-IR, absorption and luminescence spectroscopy in the temperature range of 300 - 77 K. The rate constants of radiative (Arad) and non-radiative (Anrad) transitions, intrinsic (QLnLn) and overall (QLnL) emission quantum yields, sensitization efficiency (ηsens), the experimental and theoretical intensity parameters (Ωλ), the forward (WS, WT) and backward (WbS, WbT) intramolecular energy transfer (IET) rates were determined. Magnetic properties of Tb3+ compounds were studied in a constant field of 0.5 T in the temperature range of 1.8–300 K. Dynamic AC magnetic susceptibility measurements were carried out as a function of temperature and frequency for 1Tb and 2Tb. Only in the case of 2Tb, in the presence of an external DC field, a slight temperature dependence of in-phase χ′ and out-of-phase χ'' susceptibility was recorded. Based on experimental and theoretical results, the significant effect of counterion on the photophysical and magnetic properties of RE chelates has been demonstrated and clarified, providing valuable guidance for the design of bifunctional electromagnetic radiation converters.

Polymeric dichlorido-bridged copper(II) offset stacked dimer coordination compounds and molecular spin stairs

A family of oxygen coordinated dichlorido-bridged n-X-2-pyridone (1, n = 3, X = Cl; 2, n = 3, X = Br; 3, n = 4, X = Cl; 4, n = 4, X = Br; 5, n = 5, X = Cl; 6, n = 5, X = Br) Cu(II) offset stacked dimer compounds, denoted molecular spin stairs, have been prepared and analyzed by single-crystal X-ray diffraction (1–4), powder X-ray diffraction (1–6), and variable temperature magnetic susceptibility measurements (1–6). Ferromagnetism is dominant in all compounds with a weaker antiferromagnetic exchange present in 1–4. The ferromagnetic exchange correlates to increased twist angles which are defined by the extent of the tetrahedral distortion of the copper coordination sphere and the identity of the halogen on the ring. The compounds were qualitatively fit to a ferromagnetic Heisenberg chain model with a Curie-Weiss interchain correction. The general Hamiltonian used is of the form H = − J ∑ S 1 S 2 . The ratio of exchange energies denoted α ( α = J FM | J AFM | ) ranges between 2.6 and 4.7. This family of compounds constitutes possible S = ½ Haldane-like materials.

Synthesis, structure, and magnetic properties of lanthanide(III) complexes incorporating a tris-chelate cobalt(III) complex as a metalloligand

A series of CoIII–LnIII–CoIII trinuclear complexes [Ln{Co(Hmtimn)3}2](NO3)3 were prepared by following a simple one-pot synthesis method, mixing an unsymmetrical bidentate ligand 2-(2-imidazolinyl)-6-methoxypheol (H2mtimn) with Co(NO3)2·6H2O and LnX3· 6H2O (where Ln = La, Ce, Pr, Nd, Gd or Dy and X = NO3 − or Cl−) in methanolic solution in the presence of triethylamine in air. In the reaction mixture, this leads to the in situ formation of a tris-chelate CoIII metalloligand unit, which can coordinate LnIII ions through the interactions of phenolato- and methoxy-O donors. X-ray structural analysis revealed that the CoIII metalloligand functions as a rigid tripodal ligand to coordinate to a LnIII ion by six oxygen donors. The two metalloligands in the complex exhibit homochiral aggregation (ΔΔ or ΛΛ) upon coordination to the LnIII ion. The coordination of the central LnIII ion was found to be a distorted icosahedral geometry. Magnetic susceptibility measurements reveal that both cobalt and central lanthanide ions exist in trivalent states.

Effect of cobalt doping on the structural, magnetic, optical, and electronic properties of LiFeCr4O8

Cobalt doping's influence on the structural, magnetic, and electronic properties of the double spinel LiFeCr4O8 was systematically investigated. Rietveld refinement revealed a consistent increase in lattice parameter a and unit cell volume with cobalt incorporation. Magnetic susceptibility measurements indicated three distinct transitions: an increase in the ferrimagnetic transition temperature (TN), a decrease in the magnetostructural transition temperature (TMS), and an increase in the spin gap transition by cobalt doping. Through diffuse reflectance spectroscopy the direct optical band gap (Eog) was obtained with values of 1.169 eV, 1.303 eV, 1.396 eV, and 1.230 eV for x = 0.0, 0.1, 0.2, and 0.5, respectively. The observed increase in Eog with cobalt doping suggests a widening of the band gap, which could be beneficial for optoelectronic applications. By means of X-ray photoelectron spectroscopy (XPS) the core levels of Li 1s, Co 3p, Fe 3p, Cr 3p, Fe 2p, Cr 2p, and O 1s were identified. XPS valence band (VB) analysis revealed a decreasing intensity at binding energy BE = 0 eV with respect to x = 0.0. Density functional theory calculations with Hubbard U correction (DFT + U) confirmed a ferrimagnetic semiconductor behavior with a direct electronic band gap (Eeg) of 1.085 eV.

Constructing Alkyl Chain Modified FeII Spin Crossover Complexes through Complementary Pair Strategy

AbstractFour alkyl chains and cyclohexane modified FeII complexes [Fe(Ln)(L’)](ClO4)2⋅solv (n=1, 2, 3, 4) were synthesized and characterized. X‐ray diffraction study showed that these complexes were constituted by asymmetric mononuclear FeII entities, incorporating alkyl‐chain‐modified bppCOOH (2,6‐bis(1H‐pyrazol‐1‐yl)isonicotinic acid) ligands and 6,6’’‐2,6‐dimethoxyphenyl‐substituted terpy ligand (L’). Magnetic susceptibility measurements revealed that complexes 1, 2, and 3 were in the high spin state across the measured temperature range, whereas complex 4 displayed an incomplete spin crossover phenomenon, with a transition temperature (T1/2) at 240 K. Investigations into variable‐temperature structure and magneto‐structural correlations revealed that the integration of alkyl‐chain‐modified bipyridyl units fostered the π⋅⋅⋅π intra‐ and intermolecular interactions, contributing to distinct crystal stacking and spatial configurations in complex 4 when compared to its counterparts. These findings underscore the pivotal influence of intramolecular interactions on the FeII spin states and highlight the significance of designing flexible ligands for modulating spin‐crossover characteristics.

Dual dome-like superconductivity in CuIr2Te3.85S0.15-xSex chalcogenides

In this paper, we report the superconductivity (SC) evolution on Se-substitution CuIr2Te3.85S0.15 telluride chalcogenide. The results of powder X ray-diffraction (PXRD) show that CuIr2Te3.85S0.15Se0.15-x (0≤x ≤ 0.15) series maintain a layered triangular structure and the space group are P3-m1 (No.164). Both the lattice constants a and c increase with increasing Se content. To systematically characterize the superconductivity properties, the electrical, magnetic, and thermal properties of the CuIr2Te3.85S0.15Se0.15-x (0≤x ≤ 0.15) series were tested. The resistivity and magnetic susceptibility measurements reveal that when Se gradually replaces S, CuIr2Te3.85S0.15Se0.15-x remains superconducting at low temperatures and does not disappear or transform into other electron ground states. In addition, With the increase of Se doping, the superconducting critical temperature (Tc) Rises and then falls twice, so the Tc value has two peaks in CuIr2Te3.85S0.15Se0.15-x (0≤x ≤ 0.15) series. Finally, we plot a phase plot of the superconducting transition temperature (Tc) versus the x content, which shows a "double dome" shape. CuIr2Te3.85S0.15Se0.15-x retains the inhibitory effect on CDW as the host CuIr2Te3.85S0.15. This peculiar change in superconducting transition temperature may be due to the change in the density of states at the Fermi surface caused by Se doping.

Temperature-Dependent Products in Gallium Flux Reactions of Cerium and Transition Metals.

Reactions of cerium and transition metals in excess molten gallium were carried out, exploring the formation of different cerium intermetallics as the flux reaction is cooled. Ce/T/Ga reactions with T = Ni, Cu, Pd, Ag, and Zn produce a high-temperature product, which converts into a low-temperature product in the flux. The phases present in the flux mixture were determined by quenching identical reactions at 750 and 300 °C and identifying the isolated products using elemental analysis and X-ray diffraction. The compounds CeGa2, CeCu0.37Ga3.63, CePd0.32Ga3.68, Ce5Ag1.76Ga17.29, and Ce5Zn1.37Ga17.73 were isolated by quenching at 750 °C. Upon cooling to 300 °C, the corresponding reactions instead yielded CeGa6, Ce2CuGa12, Ce2PdGa12, Ce2Ag0.7Ga9.1, and CeZnxGa7-x. All of these structures contain cerium in the ThCr2Si2-related layers. Large crystals of high-temperature products CeCu0.37Ga3.63, CePd0.32Ga3.68, Ce5Ag1.76Ga17.29, and Ce5Zn1.37Ga17.73 were used for magnetic susceptibility measurements. All of these materials show highly anisotropic ferromagnetic ordering of Ce3+ moments below 8 K, which is in contrast to the antiferromagnetism seen for the compounds that were isolated at 300 °C.

Quantitative susceptibility mapping as an early neuroimaging biomarker for amyotrophic lateral sclerosis: A review

AbstractQuantitative susceptibility mapping (QSM) is an advanced post‐processing technique in magnetic resonance imaging that offers precise measurements of tissue magnetic susceptibility with impressive spatial resolution and sensitivity. This review examines the potential of QSM as a biomarker for early detection and monitoring of amyotrophic lateral sclerosis (ALS). Since 2015, studies have consistently reported increased QSM values in the motor regions of individuals with ALS, indicating significant iron deposition. Iron accumulation is associated with dysfunction of the upper motor neurons and faster disease progression. Notably, increased QSM values were also observed in the critical subcortical areas responsible for motor function and cognitive control. However, standardizing optimized protocols, including background field removal algorithms, phase unwrapping approaches, and methods for final susceptibility map reconstruction, has the potential to enhance the consistency and reliability of QSM as an ALS biomarker. Overall, the current body of evidence strongly supports QSM in detecting iron dysregulation associated with neurodegeneration in both motor and extra‐motor regions in ALS. Furthermore, QSM's remarkable sensitivity to early pathological iron changes and its high specificity in distinguishing ALS positions make it a promising diagnostic and progression‐tracking biomarker.

Synthesis, characterization, crystal structure, molecular dynamics simulations, MM-GBSA analysis, and bioactivity studies of pyrazine- and pyrimidine-modulated unsymmetrical dipyridylamide complexes

By using unsymmetrical pyrazine- and pyrimidine-modulated oligo-α-pyridylamine ligand N-(4-methylpyrimidin-2-yl)pyrazin-2-amine (Hmpmpza) (1), 1D copper(II) coordination polymer {[Cu(mpmpza)(CH3COO)](CH3OH)(H2O)}n (2) and mononuclear copper(II) complex [Cu(Hmpmpza)(NO3)2] (3) were first successfully synthesized and structurally characterized. In complex (2), Cu(II) is six-coordinated in an elongated octahedral geometry. The Hmpmpza molecule coordinates with the Cu(II) as a tridentate ligand, in which the pyrimidine and amine group nitrogen atoms link the coordination units to an infinite 1-D chain polymer. Extensive hydrogen bonds between amino groups, acetate anions, methanol, and water molecules are observed in 2, resulting in a 3D network of the 2. Complex 2 provides the first example of the complex with a modulated Hdpa ligand, in which nitrogen atoms both of the pyrazine and pyrimidine cycles participated in the coordination with the metal center. There are two crystallographically independent molecules in a mononuclear complex 3 and the Cu(II) atom is six-coordinated in an elongated octahedral geometry. Hmpmpza in complex 3 coordinates to the Cu(II) in an anti-anti conformation as a bidentate ligand. The hydrogen bonds between amino groups and coordinated nitrate anions in complex 3, link its molecules to a 1-D chain structure. However, no hydrogen bonding linkage between the 1-D chains is observed. The temperature dependence magnetic susceptibility measurement for complex 2 described by the Bonner-Fischer approximation shows a weak antiferromagnetic coupling between Cu(II) ions. The best fitting results were obtained with parameters g = 2.141, J = −0.73 cm−1 and R = 4.85 × 10−6. The molecular dynamics (MD) simulations of the 2-hAChE, 3-hAChE, 2-hBChE, and 3-hBChE complexes offer comprehensive insights into the stability and dynamic behavior of ligand-protein interactions. These findings contribute to a detailed understanding of the specific dynamics governing the stability of acetylcholinesterase and butyrylcholinesterase complexes.

Cobalt(II) Single-Ion Magnet Coordinated by Double Deprotonation of 2,2'-Bipyridine-6,6'-diol Ligands.

In this study, we synthesized a new Co(II) complex, [NMe4]2[Co(bpyO2)2] (1), using deprotonated 2,2'-bipyridine-6,6'-diol ligands (bpyO2 2-). This compound exhibits a significant zero-field splitting (D) value. The far-infrared magneto spectroscopy and high-frequency and field electron paramagnetic resonance (HFEPR) measurements indicated that compound 1 possesses D = -54.8 cm-1 and E ∼ 0 cm-1. These findings were subsequently confirmed by other experimental data, including DC magnetic susceptibilities and variable temperature and variable magnetic field reduced magnetizations. Additionally, we conducted a series of AC magnetic susceptibility measurements to investigate the kinetics of magnetization relaxation. Below 6.6 K and under zero external magnetic field, fast quantum tunneling of magnetization (QTM) dominates (∼570 Hz), and temperature-independent out-of-phase signals are observed. Above 8.1 K, temperature-dependent behavior is observed. Furthermore, we examined the AC magnetic susceptibility behavior under external magnetic fields ranging from 300 to 4000 G. The effect of QTM is significantly reduced in the presence of an external magnetic field. Temperature-dependent behavior is primarily governed by Raman relaxation. Through structural analysis of compound 1 and a series of pure nitrogen-coordinated single-ion magnets (SIMs), we propose that the oxo substituents from the double-deprotonated form of the 2,2'-bipyridine-6,6'-diol ligands donate their negative charge to the pyridine ring, forming amido anion sites. This triggers a more pronounced out-of-phase signal than that observed in pure pyridine-coordinated compounds. Moreover, we observed intermolecular interactions, including intermolecular hydrogen bonding, which, to some extent, influenced the slow relaxation of molecules. Therefore, we speculate that the slow relaxation phenomenon of compound 1 may be attributed to the combination of oxo back-donating effects and intermolecular interactions.

Preparation, Characterization and Biological Activity of some Metals (II) with Glycine Complexes

In this work-study metals (II) coordination compound of Glycine were preparation and characterized using by infrared and UV-V is spectroscopy technique and Magnetic Susceptibility Measurements (BM). The complexes were studed for biological activity (an antibacterial activity of the complex).The stoichiometric the reaction between the metal(II) ion and ligands ion molar ratio(1:2)[where M= Ni,Co, Zn and glycine].

Enhancement in Anticancer Activity of Chitosan Tailored Imidazole-2-Thiosemicarbazones against MCF-7 Cancer Cell Line by Coordination with Copper(II) Ions

The coordination behavior of new batch synthesized chitosan imidazole-2-thiosemicarbazones tailored from both the low molecular weight commercial chitosan and high molecular weight crab shell chitosan was confirmed by Fourier Transform Infrared (FT-IR) and magnetic susceptibility measurements. Chlorine content in the complexes was estimated by potentiometric titration technique. The study showed the tridentate NNS tridentate coordination with copper (II) ion in a square planar orientation with the remaining valence satisfied by coordination with chloride ion. The MTT assay studies showed an enhancement in the anticancer activity of these chitosan thiosemicarbazone ligands upon their coordination with copper (II) ions against the human breast cancer (MCF-7) cell line in vitro. The minimal cytotoxicity of both the ligands and complexes against the normal mouse embryonic fibroblast (NIH3T3) cells revealed the selective attraction of these biomaterial chitosan derivatives towards the cancer cells with non-toxicity to healthy cells. There was only a marginal effect of molecular weight (Mw) and degree of deacetylation (DDA) of chitosan upon the anticancer activity of these chitosan derivatives.

Measurement of the Axial Magnetic Susceptibility of m-SWCNTs at High Temperatures in a Magnetic Field-Assisted FC-CVD.

We synthesized some SWCNTs films under different magnetic fields and temperatures in a magnetic field-assisted FC-CVD and obtained Raman spectra of the films. By analyzing the Raman spectra, it was concluded that the SWCNTs films had defects, and the relative content of m-SWCNTs in the SWCNTs films was obtained. The trajectory of m-SWCNTs was obtained by analyzing the motion behavior of m-SWCNTs flow in the field-assisted system, and a model was built to describe the relationship between the relative content of m-SWCNTs and magnetic fields. The axial magnetic susceptibility of m-SWCNTs as a parameter was obtained by fitting the experimental results and the model. This is the first time that the axial magnetic susceptibility of m-SWCNTs has been obtained. The result obtained at 1273 K is at least two orders of magnitude greater than the magnetic susceptibilities and anisotropies of purified m-SWCNTs at 300 K, indicating that the defects increase the Curie temperature and Curie constant of m-SWCNTs. This is consistent with the spin-polarized density functional theory, which predicts that m-SWCNTs with vacancies have local magnetic moments around the vacancies and exhibit ferro- or ferrimagnetism.

Ce3Bi4Ni3 – A large hybridization-gap variant of Ce3Bi4Pt3

The family of cubic noncentrosymmetric 3-4-3 compounds has become a fertile ground for the discovery of novel correlated metallic and insulating phases. Here, we report the synthesis of a new heavy fermion compound, Ce3Bi4Ni3. It is an isoelectronic analog of the prototypical Kondo insulator Ce3Bi4Pt3 and of the recently discovered Weyl-Kondo semimetal Ce3Bi4Pd3. In contrast to the volume-preserving Pt-Pd substitution, structural and chemical analyses reveal a positive chemical pressure effect in Ce3Bi4Ni3 relative to its heavier counterparts. Based on the results of electrical resistivity, Hall effect, magnetic susceptibility, and specific heat measurements, we identify an energy gap of 65–70 meV, about eight times larger than that in Ce3Bi4Pt3 and about 45 times larger than that of the Kondo-insulating background hosting the Weyl nodes in Ce3Bi4Pd3. We show that this gap as well as other physical properties do not evolve monotonically with increasing atomic number, i.e., in the sequence Ce3Bi4Ni3−Ce3Bi4Pd3−Ce3Bi4Pt3, but instead with increasing partial electronic density of states of the d orbitals at the Fermi energy. This work opens the possibility to investigate the conditions under which topological states develop in this series of strongly correlated 3-4-3 materials. Published by the American Physical Society 2024

Mononuclear Fe(III) Schiff Base Complex with Trans-FeO4N2 Chromophore of o-Aminophenol Origin: Synthesis, Characterisation, Crystal Structure, and Spin State Investigation

A new iron(III) complex (Et3NH)2[Fe(L)2](ClO4)·MeOH (1) where H2L = 2-{(E)-[2-hydroxyphenyl)imino]methyl}phenol has been synthesised and characterised by single crystal XRD, elemental analysis and DC magnetic susceptibility measurements. The dianionic ligands L2− coordinate in a tridentate fashion with the Fe(III) through their deprotonated phenolic oxygens and azomethine nitrogen atoms, resulting in a trans-FeO4N2 chromophore. Variable-temperature magnetic measurements were performed between 300 and 5 K under an applied field of 0.1 T and show that 1 is in the high spin state (S = 5/2) over the whole measured temperature range. This is confirmed by Mössbauer spectroscopy at 77 and 300 K.

Dynamic Magnetic Susceptibility Method in Studies of Coordination Compounds

The measurement of the dynamic magnetic susceptibility is a universal method, which is used for the evaluation of magnetic properties of single molecule magnets by scientists all over the world. An information in the Russian scientific literature that can be useful for practical mastering of this method is presently insufficient. To fill this gap, in this work we present a detailed procedure of a magnetochemical experiment for observing slow magnetic relaxation in coordination compounds of 3d- and 4f-element ions and the complete characterization of the dynamics of the magnetic behavior. Special attention is given to usually omitted but important details related to all stages of studying the magnetic relaxation dynamics. The main variants of sample preparation are described, the logics of the construction of a measuring sequence and the procedure of experimental data processing are discussed, and advantages and drawbacks of some programs of the calculation of magnetic relaxation dynamics data are considered. The main concepts and equations used in experimental data analysis are presented, and the primary conclusions that can be made from the obtained results are proposed.

Concurrence of directional Kondo transport and incommensurate magnetic order in the layered material AgCrSe2

In this work, we report on the concurrent emergence of the directional Kondo behavior and incommensurate magnetic ordering in a layered material. We employ temperature- and magnetic field-dependent resistivity measurements, susceptibility measurements, and high resolution wavelength X-ray diffraction spectroscopy to study the electronic properties of AgCrSe2. Impurity Kondo behavior with a characteristic temperature of TK = 32 K is identified through quantitative analysis of the in-plane resistivity, substantiated by magneto-transport measurements. The excellent agreement between our experimental data and the Schlottmann’s scaling theory allows us to determine the impurity spin as S = 3/2. Furthermore, we discuss the origin of the Kondo behavior and its relation to the material’s antiferromagnetic transition. Our study uncovers a rare phenomenon—the equivalence of the Néel temperature and the Kondo temperature—paving the way for further investigations into the intricate interplay between impurity physics and magnetic phenomena in quantum materials, with potential applications in advanced electronic and magnetic devices.

Synthesis, disorder and Ising anisotropy in a new spin liquid candidate PrMgAl11O19

Here we report the successful synthesis of large single crystals of triangular frustrated PrMgAl11O19 using the optical floating zone technique. Single crystal x-ray diffraction (XRD) measurements unveiled the presence of quenched disorder within the mirror plane, specifically ~7% of Pr ions deviating from the ideal 2d site towards the 6h site. Magnetic susceptibility measurements revealed an Ising anisotropy with the c-axis being the easy axis. Despite a large spin–spin interaction that develops below ~10 K and considerable site disorder, the spins do not order or freeze down to at least 50 mK. The availability of large single crystals offers a distinct opportunity to investigate the exotic magnetic state on a triangular lattice with an easy axis out of the plane.