Curie-Weiss Constant Research Articles

Harnessing the half-metallicity and thermoelectric insights in Cs2AgMBr6 (M = V, Mn, Ni) double halide perovskites: A DFT study

Herein, we undertake a detailed exploration of the structural stability, magneto-electronic behavior, and thermoelectric properties of Cs₂AgMBr₆ (M = V, Mn, Ni) halide double perovskites using first-principles approach. The study commences with a meticulous assessment of both structural stability and thermodynamic properties employing various metrics. Energy minimization across different phases, utilizing the Birch-Murnaghan equation of state, confirms the ferromagnetic phase as energetically favoured, supported by Curie-Weiss constants of 98 K, 100 K, and 150 K for V, Mn, and Ni-based perovskites, respectively. Mechanical properties, including hardness, stiffness, ductility, and fracture strength, are derived from the simulated elastic constants, ensuring the mechanical stability of the materials. Electronic structure analysis, performed using the PBE-GGA and GGA + mBJ functionals, reveals that Cs₂AgMBr₆ compounds exhibit half-metallic ferromagnetism, with 100 % spin polarization at the Fermi level. Analysis of the partial density of states highlights the half-metallic ferromagnetic mechanism, confirming predominant ferromagnetic order through parameters such as the exchange splitting energy (Δx), p-d exchange interaction energy (Δx(p-d)), crystal-field energy (Ecrys), and exchange constants (N₀α and N₀β). The negative values of the exchange constants further validated the dominant ferromagnetic order in both s-d and p-d interactions, with unpaired electrons contributing magnetic moments of 2 μB for V, 4 μB for Mn, and 1 μB for Ni-based perovskites. Also, the Curie temperatures are calculated as 385 K, 747 K, and 204 K for V, Mn, and Ni-based perovskites. The overall findings, which reveal 100 % spin polarization and high zT values, underscore the significant potential of Cs₂AgMBr₆ halide perovskites for advancing spintronics and thermoelectric applications.

Pioneering computational insights into the structural, magnetic, and thermoelectric properties of A3XN (A=Co, Fe; X=Cu, Zn) anti-perovskites for advanced material applications

This study pioneers the utilization of computer-controlled simulations to elucidate the structural, elastic, electronic, and thermoelectric properties of A3XN anti-perovskites (A = Co, Fe; X = Cu, Zn). Starting with the development of a detailed structural model, structural optimization calculations identify the stable Pm-3m cubic phase, aligning with experimental findings. Also, these optimizations indicate the ferromagnetic phase stability of A3XN anti-perovskites, further supported by positive Curie-Weiss constants of 60 K, 80 K, and 100 K for Co₃CuN, Co₃ZnN, and Fe₃CuN, respectively. The spin-dependent electronic properties, including band structure and density of states, are explored using multiple exchange-correlation (XC) functionals—GGA, GGA + U, and GGA + mBJ. The results uphold the metallic nature of the materials, accompanied by significant spin magnetic moments. Specifically, the calculated values of magnetic moments for Co3CuN, Co3ZnN, and Fe3CuN are 5.08 μB, 3.70 μB, and 7.61 μB, respectively. Furthermore, we compute the Curie temperatures for each compound, 942.48 K for Co3CuN, 692.7 K for Co3ZnN, and 1400.41 K for Fe3CuN, which are substantially elevated, indicating robust ferromagnetic behavior that persists well above ambient conditions. Mechanical properties, including stability, deformation behavior, and ductility, are validated through elastic calculations, with various mechanical anisotropy factors examined. From an application perspective, the thermoelectric characteristics of Co3CuN, Co3ZnN, and Fe3CuN are meticulously evaluated, focusing on parameters like the Seebeck coefficient, electrical conductivity, thermal conductivity, power factor and figure of merit (zT). The analysis highlights promising power factor values of 3.0×1011(W/cm.K2), 4.0×1011(W/cm.K2), and 6.0×1011(W/cm.K2) for Co3CuN, Co3ZnN, and Fe3CuN, respectively, suggesting potential for enhanced efficiency in thermopower generation, particularly in waste heat recovery applications. Furthermore, the study provides a comprehensive analysis of the ground-state optical properties of A3XN, including the dielectric constant, photoconductivity, reflectivity, refractive index, absorption coefficient, and extinction coefficient. The reflectivity spectra demonstrate high reflectivity of 45 % across visible and ultravioletregions, suggesting suitability for applications in coatings designed to mitigate solar heating effects.

Fabrication of Textured 0.685(Na0.5Bi0.5)TiO3-0.065BaTiO3-0.25SrTiO3 Electrostrictive Ceramics by Templated Grain Growth Using NaNbO3 Templates and Characterization of Their Electrical Properties

Electrostrictive materials based on (Na0.5Bi0.5)TiO3 are promising lead-free candidates for high-precision actuation applications, yet their properties require further improvement. This study aims to enhance the electromechanical properties of a predominantly electrostrictive composition, 0.685(Na0.5Bi0.5)TiO3-0.065BaTiO3-0.25SrTiO3, by using templated grain growth. Textured ceramics were prepared with 1~9 wt% NaNbO3 templates. A high Lotgering factor of 95% was achieved with 3 wt% templates and sintering at 1200 °C for 12 h. Polarization and strain hysteresis loops confirmed the ergodic nature of the system at room temperature, with unipolar strain significantly improving from 0.09% for untextured ceramics to 0.23% post-texturing. A maximum normalized strain, Smax/Emax (d33*), of 581 pm/V was achieved at an electric field of 4 kV/mm for textured ceramics. Textured ceramics also showed enhanced performance over untextured ceramics at lower electric fields. The electrostrictive coefficient Q33 increased from 0.017 m4C−2 for untextured ceramics to 0.043 m4C−2 for textured ceramics, accompanied by reduced strain hysteresis, making the textured 0.685(Na0.5Bi0.5)TiO3-0.065BaTiO3-0.25SrTiO3 composition suitable for high-precision actuation applications. Dielectric properties measured between −193 °C and 550 °C distinguished the depolarization, Curie–Weiss and Burns temperatures, and activation energies for polar nanoregion transitions and dc conduction. Dispersive dielectric constants were found to observe the “two” law exhibiting a temperature dependence double the value of the Curie–Weiss constant, with shifts of about 10 °C per frequency decade where the non-dispersive THz limit was identified.

A nanochanneled silver-deficient oxalatocobaltate(III) complex anion with hydronium as counter cation: Synthesis, crystal structure, thermal analysis and magnetism

A novel cobalt(III) salt, (H3O)0.6[Ag2.4Co(C2O4)3]·6H2O (1), a member of the rare paramagnetic CoIII-open framework materials, has been synthesized in water and characterized by standard methods, including elemental and thermal analyses, IR, UV-Vis and EDX spectroscopies, and single-crystal X-ray diffraction. Compound 1 crystallizes in the monoclinic I2/a space group. In the crystal structure, the Co(III) centers are pseudo-octahedrally chelated by three oxalato ligands with usual propeller orientation. The structure can be best described as an anionic silver-deficient oxalatocobaltate(III) [Ag2.4Co(C2O4)3]0.6- framework with isolated nanochannels parallel to the a axis, hosting highly disordered water molecules carrying protons (hydronium ions). Thermal analysis showed significant weight losses corresponding to the elimination of crystal water molecules followed by the decomposition of the network. Temperature-dependence susceptibility measurements investigated in the temperature range 2–300 K revealed antiferromagnetic ordering at low temperatures (T ≤ 25 K), the Curie–Weiss constants being C = 1.60 emu Oe−1 K and θ = -50 K.

Low-energy spin dynamics in a Kitaev material Na3Ni2BiO6 investigated by nuclear magnetic resonance

Abstract We perform 23Na nuclear magnetic resonance (NMR) and magnetization measurements on an S = 1, quasi-2D honeycomb lattice antiferromagnet Na3Ni2BiO6. A large positive Curie–Weiss constant of 22.9 K is observed. The NMR spectra at low fields are consistent with a zigzag magnetic order, indicating a large easy-axis anisotropy. With the field applied along the c * axis, the NMR spectra confirm the existence of a 1/3-magnetization plateau phase between 5.1 T and 7.1 T. The transition from the zigzag order to the 1/3-magnetization plateau phase is also found to be a first-order type. A monotonic decrease of the spin gap is revealed in the 1/3-magnetization plateau phase, which reaches zero at a quantum critical field H C ≈ 8.35 T before entering the fully polarized phase. These data suggest the existence of exchange frustration in the system along with strong ferromagnetic interactions, hosting the possibility for Kitaev physics. Besides, well below the ordered phase, the 1/T 1 at high fields shows either a level off or an enhancement upon cooling below 3 K, which suggests the existence of low-energy fluctuations.

Ca/Sn concentration-dependent enhancement of barium titanate ferroelectric performance: a dielectric and microstructural study

This work involved the synthesis of compositions of Ba0.95Ca0.05SnxTi1-xO3 (BCST) with varying amounts of Sn dopant (x = 0, 0.02, 0.04, 0.06, 0.08, and 0.1). A standard solid-state reaction approach was used to create all of the ceramic compounds. Each BCST composite’s microstructure, sintering, morphology, density, optical, and electrical characteristics were carefully examined, and the dielectric performance was optimized. In comparison to the unmodified composite, introducing varied amounts of Sn material into the BCST compound changed the crystal lattice vibrations and functional group locations. This result indicates that there are some variations in unit cell size, revealing that Sn+4 ions diffused effectively inside the lattice structure to produce BSCT composites. Further, SEM micrographs indicated proportionate changes in the homogenous structure and irregular forms as Sn concentration increased, as well as some variation in average grain size. As a consequence, by adding 0.08 mol% of Sn dopant, the crystallite size and average grain size were adjusted to 45.69 nm and 0.66 µm, respectively. Meanwhile, the 0.08-Sn specimen displayed a dielectric constant (Ɛ) with an optimum value of 5557 and a relative decrease in the Curie-Weiss constant. These results are attributed to the existence of various concentrations of Sn ions at the Ti-site of the BCT, which resulted in a compositionally disordered state. This disordered condition is essential for the production of dielectric compounds. Therefore, it is evident that modifying the amount of Sn doping added significantly enhanced the dielectric characteristics of the BCST composites created in this work. However, excessive Sn doping reduces the dielectric properties due to a reduction in tetragonal phase and an increase of disorders and charge fluctuations.Graphical

Stuffed Rare-Earth Garnets.

We report the synthesis and magnetic characterization of stuffed rare-earth gallium garnets, RE3+xGa5-xO12 (RE = Lu, Yb, Er, Dy, Gd), for x up to 0.5. The excess rare-earth ions partly fill the octahedral sites normally fully occupied by Ga3+, forming disordered pairs of corner-shared face-sharing magnetic tetrahedra. The Curie-Weiss constants and observed effective moments per rare-earth are smaller than are seen for the unstuffed gallium garnets. No significant change in the field-dependent magnetization is observed but missing entropy is seen when integrating the heat capacity down to 0.5 K.

Electrical and magnetic properties of MF/CuAl nanocomposites

Abstract This study investigated the effects of CuAl2O4 (CuAl) on four types of spinel ferrites: CoFe2O4 (CoF), NiFe2O4 (NiF), MgFe2O4 (MgF), and ZnFe2O4 (ZnF) with regards to their electrical characteristics and microscopic magnetic behavior. According to the Seebeck coefficient (φ), the nanocomposites have a mixture of positive and negative charge carriers, except for CoF/CuAl, which has a positive charge carrier only. Depending on the temperature, the DC conductivity of all MF/CuAl nanocomposites has a conductor and semiconductor behavior. The dielectric properties were studied at different frequencies (100–10^8 Hz) and temperatures (300–673 K). The results demonstrated how temperature and frequency affect AC operating mechanisms. The high values of dielectric loss for all nanocomposites confirm their applicability in high-frequency microwave devices. The impedance study revealed that the equivalent circuit for all MF/CuAl nanocomposites is a mixture of R, L, and C. Temperature-magnetization graphs were obtained for all nanocomposites, indicating ferrimagnetic behavior except ZnF/CuAl. The magnetic transition temperature (T Cm), the Curie–Weiss constant (θ CW), and the effective magnetic moments (μ eff) for all nanocomposites were determined. The MF/CuAl samples were analyzed using ESR spectroscopy at room temperature. The spectra were distorted but remained distinct, potent, and sweeping. The g-factor values deviate from the free electron, which suggests that the Fe3+–O–Fe3+ superexchange interaction has changed. In addition, the interaction effect between MF and CuAl is discussed.

Molecular-orientation-dependent magnetic properties of iron phthalocyanine (FePc) thin films and microwires

The development of molecular magnets plays a major role in emerging organic spintronics applications, as it exhibits both semiconducting and magnetic properties. Herein, we report on the molecular-orientation-dependent magnetic properties of iron phthalocyanine (FePc) thin films and microwires. FePc thin films grown on SiO2 and flexible kapton substrates clearly reveal that the morphology is strongly influenced by the substrates and film thickness. Meanwhile, the molecular stacking orientation of FePc thin films can be tuned by 3, 4, 9, 10-perylenetetracarboxylic dianhydride (PTCDA) templating layer and film thickness. Magnetic hysteresis loops show that the iron atoms are strongly magnetically coupled into ferromagnetic chains at low temperature with high coercivity at 1000 Oe. The magnetization and susceptibility of FePc thin films are dependent on the molecular orientation, and the Curie–Weiss constant is modulated from 24 ± 2 K K to 35 ± 2 K through the templating effect, in which the molecular stacking orientation changes from standing-up to lying-down arrangement. Furthermore, strong orientation dependent ferromagnetism is also observed in low-dimensional η-FePc microwires, in which the Curie–Weiss constants change from 20 ± 2 K to 35 ± 2 K when magnetic field rotated from short wire axis to long wire axis. The ability to fabricate FePc thin films on flexible substrate with controllable molecular orientation and ferromagnetism makes them promising candidates for flexible spintronic devices.

Synthesis, single crystal structure, optical and magnetic properties of a new rubidium nickel iron phosphate RbNiFe(PO4)2

New RbNiFe(PO4)2 phosphate, both in single and powder forms, was synthesized by flux method and solid state reaction. It is characterized by crystal-X-ray diffraction, HRTEM, IR and Raman spectroscopy and UV-diffuse reflectance. Its crystal structure adopts the monoclinic P21/c space group with the cell parameters: a= 5.134(4) Å, b= 14.547(2) Å, c= 9.230(2) Å; β=103.76(3) ° and Z= 4. The RbNiFe(PO4)2 framework has a three-dimensional structure, consisting of chains of edge-sharing NiO6, isolated FeO5 and PO4 tetrahedra sharing vertices and edge to form large tunnels along the [100] direction, where Rb + cations are placed. The IR and Raman data are in good agreement with the number of PO4 groups determined in crystal structure. Diffuse reflectance spectroscopy leads to a gap energy of 3.15 eV. It also proved the presence of isolated Fe3+ ions from low energy due to the inter-electronic transition from oxygen to Ni (II) and the non-existence of d-d transition related to iron. The colorimetric properties of the compound result mainly from d-d visible transitions related to the Ni2+ cation in octahedral coordination. The magnetic study revealed that below the temperature of TN =21K an antiferromagnetic character appears with a Curie-Weiss constant of Ө = −97 K.

Effect of sintering temperature on microstructure, dielectric and ferroelectric properties of BaTiO3 ceramics

BaTiO3 ceramic powders are prepared by the solid phase reaction method. BaTiO3 ceramic powders are sintered at different temperatures for 3 h. The tetragonal phase of BaTiO3 powder is confirmed by XRD. It was found that as the sintering temperature increased, the grain size, density, and dielectric constant of BaTiO3 ceramics increased. All the BaTiO3 ceramic samples sintered at various temperatures for 3 h show the diffuse phase transition and the diffuseness parameter and curie-Weiss constant are also calculated. BaTiO3 ceramic samples sintered at 1200 °C show well-grown grain boundaries. The ferroelectric nature of sintered BaTiO3 ceramic samples studied using P-E hysteresis measurements.

Synthesis, crystal structure, electrical and magnetic properties of a novel phosphate: Ag4CoFe2(PO4)4

A new silver-cobalt-iron orthophosphate, Ag4CoFe2(PO4)4, has been elaborated in single crystal and powder forms. The crystal structure was studied using X-ray diffraction data. This new phosphate crystallizes in the monoclinic system with C2/c space group. The structure of this phosphate consists of an association of FeO6 and CoO6 octahedra, and PO4 tetrahedra sharing corners and edges leading to infinite layers perpendicular to the [010] direction. Ag+ cations reside in the interlayer space and in the cavities of the crystal framework. Furthermore, the purity of the synthesized powder was validated by X-ray powder diffraction analysis. The bands observed in the infrared and Raman spectra were attributed to the vibration modes of the PO4 tetrahedra. The electrical conductivity of this phosphate was investigated using impedance spectroscopy. The results showed an ionic conductivity of 2.6 ​× ​10−3 ​S ​cm−1 at 773 ​K with an activation energy of Ea ​= ​1.17 ​eV indicating the Ag ​+ ​mobility in the layered structure. The magnetic investigation revealed antiferromagnetic order below the temperature of TN ∼10 ​K with a Curie-Weiss constant of Ө ​= ​−119.39 ​K.

Structure, Optical and Magnetic Properties of Two Isomeric 2-Bromomethylpyridine Cu(II) Complexes [Cu(C6H9NBr)2(NO3)2] with Very Different Binding Motives.

Two isomeric 2-bromomethylpyridine Cu(II) complexes [Cu(C6H9NBr)2(NO3)2] with 2-bromo-5-methylpyridine (L1) and 2-bromo-4-methylpyridine (L2) were synthesized as air-stable blue materials in good yields. The crystal structures were different with [Cu(L1)2(NO3)2] (CuL1) crystallizing in the monoclinic space group P21/c, while the 4-methyl derivative CuL2 was solved and refined in triclinic P1¯. The orientation of the Br substituents in the molecular structure (anti (CuL1) vs. syn (CuL2) conformations) and the geometry around Cu(II) in an overall 4 + 2 distorted coordination was very different with two secondary (axially elongated) Cu-O bonds on each side of the CuN2O2 basal plane in CuL1 or both on one side in CuL2. The two Br substituents in CuL2 come quite close to the Cu(II) centers and to each other (Br⋯Br ~3.7 Å). Regardless of these differences, the thermal behavior (TG/DTA) of both materials is very similar with decomposition starting at around 160 °C and CuO as the final product. In contrast to this, FT-IR and Raman frequencies are markedly different for the two isomers and the UV-vis absorption spectra in solution show marked differences in the π-π* absorptions at 263 (CuL2) or 270 (CuL1) nm and in the ligand-to-metal charge transfer bands at around 320 nm which are pronounced for CuL1 with the higher symmetry at the Cu(II) center, but very weak for CuL2. The T-dependent susceptibility measurements also show very similar results (µeff = 1.98 µB for CuL1 and 2.00 µB for CuL2 and very small Curie-Weiss constants of about -1. The EPR spectra of both complexes show axial symmetry, very similar averaged g values of 2.123 and 2.125, respectively, and no hyper-fine splitting.

Five new isomorphic coordination polymers with large conjugated ligands: Synthesis, crystal structures and performances

Five new coordination compounds with isomorphic frameworks, {[M(cpp)2(H2O)2]·3H2O}n [M ​= ​Co (1), Cd (2), Mn (3), Ni (4), Zn (5)], were successfully synthesized through the reactions of 1-(4-carboxyphenyl)-3-(pyrazin-2-yl)pyrazole (Hcpp) and a series of transition metal salts under the solvo-thermal conditions. Compounds 1–5 were characterized by single crystal X-ray diffraction, powder X-ray diffraction, elemental analysis, infrared spectra and thermogravimetric analysis. Isomorphic compounds 1–5 display an abnormal two-dimensional helical layer containing a M4(cpp)4 cavity with the dimension of 26.21 ​× ​8.39 ​Å2. Variable-temperature magnetic susceptibility measurements indicate weak antiferromagnetic interactions with Curie constant (2.08 ​cm3 ​K ​mol−1) and Weiss constant (−6.90 ​K) in compound 1. Compounds 2 and 5 show apparently blue light emission, wherein the sensing responses to small molecules, inorganic anions and metal cations indicate compound 5 can be used as a multifunctional fluorescence probe to detect aniline, Fe3+, CrO42− and Cr2O72− through fluorescence quenching and the corresponding quenching mechanisms are proposed.

Flash sintering and dielectric properties of K0.5Na0.5NbO3

AbstractK0.5Na0.5NbO3 (KNN) of 4‐μm average particle size was flash sintered in parallel plate capacitor configuration (PPCC) under 100 V/mm (0.8 mA/mm2 cut‐off) with 10°C/min heating rate in air. Precipitous densification occurred from Tf = 662–670°C (Tf–furnace temperature) in 60 s with 55 mW/mm3 peak power absorption at Tf = 667°C, resulting in 98% dense ceramic of < 5‐μm grains size. No grain growth was observed. A cubic grain morphology was inherited from the starting KNN powder. No sign of liquid phase formation on grain boundaries (GBs) was detected. A 147°C rise above Tf = 667°C due to Joule heating is predicted. At 25°C and 1 kHz, relative permittivity (εr) and dielectric loss (tan(δ)) are 4096 and 2.9%, respectively. From 0.1 to 100 kHz, εr and tan(δ) undergo relaxation, reaching εr = 577 and tan(δ) = 0.2% at 1000 kHz. Variation of εr with temperature revealed Amm2 → P4mm and P4mm → Pm3m transitions at ∼204°C and 409°C, respectively. As per Curie–Weiss analysis, Curie temperature and Curie–Weiss constant are θ = 375°C and C = 3.1 × 10−5°C for the P4mm → Pm3m transition, respectively. The transition is first order as Ttr > θ with a diffusiveness exponent γ = 1.04, indicating normal ferroelectric behavior. The low‐frequency dielectric relaxation is attributed to the space charge in the vicinity of GBs, which is a remnant of flash sintering. Joule heating cannot alone account for the densification in 60 s, which we substantiate within the framework of phase equilibrium and diffusion kinetics. We conjecture that oxygen vacancies start ionizing at Tf = 662°C, couple with the applied electric field via the Lorentz force, and increase their electrochemical potential, causing ultrafast densification. The effects of sample shape, size, and PPCC contributing to high sintered density are also discussed.

Effect of temperature on the dielectric and magnetic properties of NiFe2O4@MgFe2O4 and ZnFe2O4@MgFe2O4 core-shell

This work discusses the experimental results of the electrical and magnetic properties of the core-shell NiFe2O4@MgFe2O4 (NiF@MgF), and ZnFe2O4@MgFe2O4 (ZnF@MgF). The conductivity behavior showed semiconductor-metallic behavior, which varies between NSPT, OSPT, and CBH models depending on the temperatures and the frequencies. In addition, the dielectric showed that a mutual effect between the core and the shell materials, which increases the polarization of the space charge. From this point of view, the nanocomposites show conductive or semiconductor behavior depending on temperature, so they have the potential in many electronic devices application. The magnetization M(T) with the Faraday balance method indicates a good magnetic property of the ZnF@MgF sample. Moreover, the effective magnetic moment (μ Eff) and the Curie-Weiss constant (θ) were obtained from the protocols χ (T).

EPR study of paramagnetic centers in SiO2:C: Zn nanocomposites obtained by infiltration of fumed silica with luminescent Zn(acac)2 solution

Silica-carbon with zinc (SiO2:C:Zn) nanocomposites obtained via infiltration with aged luminescent zinc acetylacetonate (Zn(acac)2) ethanol solution of two concentrations (1 or 4%) into the fumed silica (SiO2) matrix have been studied using EPR within the temperature range 6…296 K before and after thermal annealing. The EPR spectrum of SiO2:C:Zn nanocomposites consists of three signals with the Lorentzian lineshape corresponding to paramagnetic centers with S = 1/2, which are related to carbon dangling bonds (CDB) (g = 2.0029(3)), silicon dangling bonds (g = 2.0062(3)) and oxygen-centered carbon-related radicals (CRR) (g = 2.0042(3)). A small EPR linewidth (<1 mT) observed for CDB and oxygen-centered CRR allows us to conclude that they are in the sp3-hybridized state. It was found that the temperature dependence of the EPR signal integrated intensity of the CDB and oxygen-centered CRR follows the Curie–Weiss law with a small positive value of the Curie–Weiss constant, which indicates that the weak ferromagnetic exchange interaction takes place in the spin system of CDB and oxygen-centered CRR. It was supposed that the carbon-related centers are clustered in SiO2:C:Zn nanocomposites. We assume that the oxygen-centered CRR in the sp3-hybridized state are associated with luminescent centers in previously reported aged Zn(acac)2/C2H5OH solution.

Non-magnetic ions doping effects in the magnetic properties of zircon-type GdCrO4 compound

In this paper, we report the effect of V and Y-doping on the structural and magnetic properties of the GdCrO4 compound obtained by the co-precipitation method. The analysis of the X-ray diffraction data using the Rietveld refinement confirm the formation of a single phase consistent with the zircon-type structure (tetragonal and I41/amd space group) and a decreasing of lattice parameter with increasing of doping. The T-dependent magnetic susceptibility is consistent with a ferromagnetic and an antiferromagnetic orders for YCrO4 and GdVO4 samples, respectively. On the other hand, the positive signal of Curie–Weiss constants of doped samples indicate the predominance of ferromagnetic correlations. Furthermore, the displacement of the maximum of susceptibility and the thermal hysteresis as a function of doping can be an indication of frustration effects. Isothermal magnetization measured at T = 2 K show a change of slope at low magnetic fields for V-doped samples and a decrease of the magnetic moment for Y-doped GdCrO4. At T = 15 K, the analysis of MvsH curves reveal that only part of Gd3+ magnetic moments are ordered.

Research of the Properties of Gadolinium Stearate by EPR Spectroscopy

Gadolinium stearate is synthesized in the form of a micropowder. Its composition is determined by elemental and energy dispersive X-ray analyses: [Gd(C17H35COO)3]·(H2O)2.42. The splitting parameters in the zero field (D and E) are determined for the EPR spectrum of the gadolinium stearate powder synthesized at 77 K. The magnetic susceptibility is calculated from the integral intensities of the EPR spectra of the gadolinium stearate powder recorded in a range of 77–293 K. The Curie temperature (θ = 0.16 K) and Weiss constant (С = 7.53 cm3 K mol–1) are determined. The effective magnetic moment is calculated (μeff = 7.8 ± 0.14 μВ), which is constant in the whole temperature range studied for the synthesized gadolinium stearate powder.

RETRACTED: Two transition metal coordination polymers: Magnetic investigation and treatment activity on children chronic myocarditis by regulating the hs-cTnT expression

Abstract In the current study, by solvothermal reaction of Cu(NO3)2·3H2O or Co(NO3)2·6H2O with the H4Tdada ligand in a mixed solvent of H2O and DMA, two novel coordination polymers (CPs) were prepared and their chemical formulae are {[(CH3)2NH2]2[Co(Tdada)](H2O)3}n (1) and {[Cu2(Tdada)(H2O)(DMA)](DMA)3}n (2, H4Tdada ​= ​5,5′-((thiophene-2,5-dicarbonyl) bis(azanediyl)) diisophthalic acid). The single crystal X-diffraction studies show that compound 1 shows a 3D 2-fold interpenetrated framework with a 4-connected dia topology and compound 2 shows a non-interpenetrated framework with a 4-connected lon topology. The magnetic investigations indicate that the two compounds possess antiferromagnetic coupling between neighboring metallic ions, and the Curie-Weiss constant is −7.5 ​K for 1 and -6.04 ​K for 2, respectively. Their treatment activity on viral myocarditis was evaluated and the related mechanism was discussed at the same time. First of all, the Cell Counting Kit-8 was carried out to evaluate the toxicity of compounds 1 and 2. The Annexin V-FITC Apoptosis Detection Kit was conducted and the apoptosis of the virus infected cardiomyocytes was measured. In addition to this, the ELISA detection was used to measure the hs-cTnT in the cardiomyocytes after compound 1 or 2 treatment.