Effective Magnetic Moment Research Articles

Mono- and Disamarium Azacryptand Complexes: A Platform for Cooperative Rare-Earth Metal Chemistry.

Mono- (H3LSm) and disamarium complexes (LSm2) were prepared by reaction of the azacryptand N[(CH2)2NHCH2-p-C6H4CH2NH(CH2)2]3N (H6L) with 1 or 2 equiv of Sm[N(SiMe3)2]3, respectively. The disamarium complex features free coordination sites on both metal centers available for bridging ligands shielded by phenylenes from tetrahydrofuran (THF) coordination. The reaction of LSm2 with KCN and 18-crown-6 yielded the adduct [LSm2-μ-η1:η1-CN][K(18-crown-6)(THF)2] featuring a bridging cyanide. The complexes were characterized by crystallography, electrochemical analysis, NMR, and optical spectroscopy, and the effective magnetic moments were determined via the Evans method.

Influence of Y substitution on structural, magneto-transport, and magnetic properties of La2-xYxCoMnO6 (0 ≤ x ≤ 0.3) double perovskites

We report a comprehensive study on the correlations of structural, magnetic, and electronic properties of Y substituted double perovskite La2-xYxCoMnO6 (0 ≤ x ≤ 0.3) compounds. The Rietveld refined X-ray diffraction patterns reveal that all synthesized compounds crystallize in monoclinic structure with the P21/n space group. Raman spectra affirm the presence of well-defined bands, assigned to the double perovskite structure. The temperature dependence of electrical resistivity indicates the semiconducting nature of the compounds without any transition and is effectively probed by Variable range hopping model. The application of a magnetic field suppresses the resistivity to exhibit significant low-temperature magnetoresistance. The paramagnetic to ferromagnetic transition temperature (Tc) decreased but saturation/remnant magnetization increased with increasing Y doping. The effective magnetic moments determined by the Curie-Weiss law show a decrease in the Y concentration. The substitution of iso-valent Y at the La site induces structural compression which is strongly correlated to the enhancement of effective magnetization values.

Supercurrent diode effect, spin torques, and robust zero-energy peak in planar half-metallic trilayers

We consider trilayer ${\mathrm{F}}_{1}{\mathrm{F}}_{2}{\mathrm{F}}_{3}$ Josephson junctions that are finite in two dimensions and have arbitrary magnetizations in each ferromagnet ${\mathrm{F}}_{i}\phantom{\rule{0.28em}{0ex}}(i=1,2,3)$. The trilayers are sandwiched between two $s$-wave superconductors with a macroscopic phase difference $\mathrm{\ensuremath{\Delta}}\ensuremath{\varphi}$. Our results reveal that when the magnetizations have three orthogonal components, a supercurrent can flow at $\mathrm{\ensuremath{\Delta}}\ensuremath{\varphi}=0$. With our generalized theoretical and numerical techniques, we study the planar spatial profiles and $\mathrm{\ensuremath{\Delta}}\ensuremath{\varphi}$ dependencies of the charge supercurrents, spin supercurrents, spin torques, and density of states. Remarkably, upon increasing the magnetization strength in the central ferromagnet layer up to the half-metallic limit, the self-biased current and induced second harmonic component become dramatically enhanced while the critical supercurrent reaches its maximum value. Additionally, for a broad range of exchange-field strengths and orientations, the ground state of the system can be tuned to an arbitrary phase difference ${\ensuremath{\varphi}}_{0}$. For intermediate exchange-field strengths in the middle layer ${\mathrm{F}}_{2}$, a ${\ensuremath{\varphi}}_{0}$ state can arise that creates a superconducting diode effect, whereby $\mathrm{\ensuremath{\Delta}}\ensuremath{\varphi}$ can be tuned to create a one-way dissipationless current flow. The spin currents and effective magnetic moments reveal a long-ranged spin torque in the half-metallic phase. Moreover, the density of states unveils the emergence of zero-energy peaks for the mutually orthogonal magnetization configurations. Our results suggest that this simple trilayer Josephson junction can be an excellent candidate for producing experimentally accessible signatures for long-ranged self-biased supercurrents and supercurrent diode effects.

A Unique Mechanochemical Redox Reaction Yielding Nanostructured Double Perovskite Sr2FeMoO6 With an Extraordinarily High Degree of Anti-Site Disorder.

Strontium ferromolybdate, Sr2FeMoO6, is an important member of the family of double perovskites with the possible technological applications in the field of spintronics and solid oxide fuel cells. Its preparation via a multi-step ceramic route or various wet chemistry-based routes is notoriously difficult. The present work demonstrates that Sr2FeMoO6 can be mechanosynthesized at ambient temperature in air directly from its precursors (SrO, α-Fe, MoO3) in the form of nanostructured powders, without the need for solvents and/or calcination under controlled oxygen fugacity. The mechanically induced evolution of the Sr2FeMoO6 phase and the far-from-equilibrium structural state of the reaction product are systematically monitored with XRD and a variety of spectroscopic techniques including Raman spectroscopy, 57Fe Mössbauer spectroscopy, and X-ray photoelectron spectroscopy. The unique extensive oxidation of iron species (Fe0 → Fe3+) with simultaneous reduction of Mo cations (Mo6+ → Mo5+), occuring during the mechanosynthesis of Sr2FeMoO6, is attributed to the mechanically triggered formation of tiny metallic iron nanoparticles in superparamagnetic state with a large reaction surface and a high oxidation affinity, whose steady presence in the reaction mixture of the milled educts initiates/promotes the swift redox reaction. High-resolution transmission electron microscopy observations reveal that the mechanosynthesized Sr2FeMoO6, even after its moderate thermal treatment at 923 K for 30 min in air, exhibits the nanostructured nature with the average particle size of 21(4) nm. At the short-range scale, the nanostructure of the as-prepared Sr2FeMoO6 is characterized by both, the strongly distorted geometry of the constituent FeO6 octahedra and the extraordinarily high degree of anti-site disorder. The degree of anti-site disorder ASD = 0.5, derived independently from the present experimental XRD, Mössbauer, and SQUID magnetization data, corresponds to the completely random distribution of Fe3+ and Mo5+ cations over the sites of octahedral coordination provided by the double perovskite structure. Moreover, the fully anti-site disordered Sr2FeMoO6 nanoparticles exhibit superparamagnetism with the blocking temperature T B = 240 K and the deteriorated effective magnetic moment μ = 0.055 μ B per formula unit.

Ferromagnetic ordering in UFe0.40Ge[formula omitted] studied by [formula omitted]Fe Mössbauer spectroscopy

A polycrystalline 57Fe-isotope-enriched sample of UFe0.40Ge2 was investigated by X-ray powder diffraction, magnetization and Mössbauer spectra measurements. The compound was confirmed to crystallize with the orthorhombic CeNiSi2-type structure (space group Cmcm) and with the lattice parameters a = 4.0759(2) Å, b = 15.8107(7) Å, and c = 4.0379(2) Å, being close to those reported previously for a very similar composition. Magnetic properties measurements showed that UFe0.40Ge2 orders ferromagnetically at TC = 37 K with the effective magnetic moment of 2.57(3) μB and the ordered magnetic moment at 70 kOe of about 0.64(1) μB, being fully consistent with the earlier report on physical properties of UFe0.39Ge2. 57Fe Mössbauer spectra measurements performed both in the field-cooled and zero-field-cooled regimes ruled out the formation of ferromagnetic cluster-glass or spin-glass state, and confirmed that the ferromagnetism in the studied system is purely long-range in nature. A small contribution of about 0.24–0.36 μB to the total magnetic moment from the iron atoms was observed.

Fabrication and characterization of highly Dy3+- and Tb3+-doped germano-borate glasses for magneto-optic device applications at 1.55 μm

Highly Dy3+- and Tb3+-doped germano-borate glasses with different rare-earth ion concentrations (10−25 mol%) were fabricated and their thermal, thermo-mechanical, optical, and magneto-optic (MO) properties were investigated with respect to the rare-earth ion concentration. The glasses showed high transmission properties of > 83% in the near-infrared regions of approximately 1.5 and 2.1 μm. The MO properties of the glasses were investigated using Faraday rotation measurements at 1.5 μm. The large Verdet constants of −5.35 and −6.11 rad/(T•m) at 1.55 μm were obtained for the glasses incorporated with the highest Dy3+ and Tb3+ concentrations of 25 mol% and 16 mol%, respectively; this was due to large effective magnetic moments and electronic transition frequencies of the rare-earth ions. The results showed that the germano-borate glasses doped with high Dy3+and Tb3+ concentrations are promising MO materials for application in MO devices in the near-infrared region.

Salts of vanadyl phthalocyanine {VIVO(Pc•3−)}− anions with decamethylmetallocenium cations (Cp*2M+, M = CrIII and CoIII). Ferromagnetic coupling in the [(Cp*2Cr+){VIVO(Pc•3−)}−]2 assemblies

Vanadyl phthalocyanine {VIVO(Pc2−)}0 was reduced by decamethylchromocene or decamethylcobaltocene (Cp*2MII), and the crystals of the complexes were precipitated by n-hexane. Reduction of this phthalocyanine is centered on the macrocycle providing the formation of the {VIVO(Pc•3−)}− anions containing two paramagnetic VIV and Pc•3− centers with an S = 1/2 spin state. These paramagnetic anions coexist in (Cp*2Cr+){VIVO(Pc•3−)}−·3C6H4Cl2 (1) with the high-spin (S = 3/2) Cp*2Cr+ counter cations. Nearly isolated assemblies in which two Cp*2Cr+ cations are sandwiched between two {VIVO(Pc•3−)}− anions are formed in 1. Effective magnetic moment of 1 of 4.57 μB at 300 K corresponds to the contribution of noninteracting VIV, Pc•3− and CrIII spins. Weiss temperature of +4 K indicates weak ferromagnetic coupling of spins. Effective magnetic moment of 1 increases upon cooling up to 4.78 μB at 8 K and then drastically falls down. Such magnetic behavior is described well by ferromagnetic coupling between the VIV and Pc•3− spins with J1 = + 4.75 cm−1 and weaker ferromagnetic interactions between Pc•3− and CrIII spins through the Cp* ligand with J2 = +1.08 cm−1. Weak antiferromagnetic coupling with J3 = −0.76 cm−1 is also present between the CrIII spins. Complexes (Cp*2Co+){VIVO(Pc•3−)}−·1.5C6H4Cl2 (2) and (Cp*2Co+) {VIVO(Pc•3−)}−·C6H4Cl2 (3) with the diamagnetic Cp*2Co+ counter cations (S = 0) were also obtained allowing to study their crystal structures and optical properties.

Spectroscopic Characterization, Thermogravimetry and Biological Studies of Ru(III), Pt(IV), Au(III) Complexes with Sulfamethoxazole Drug Ligand

Complexes of Ru(III), Pt(IV), and Au(III) with sulfamethoxazole (SMX) were experimentally produced. The resulted formations of novel metal complexes were discussed using several techniques, such as effective magnetic moment molar conductivity, IR, UV, and 1H NMR spectra, elemental analyses, thermal analysis, microscopic and XRD analyses. The X-ray diffraction patterns of the solid powders of the synthesized sulfamethoxazole complexes indicated their identical formulation. The surface uniformity of the complexes’ samples was confirmed by SEM images. These complexes appear as spots, dark in appearance, with particle sizes of 100–200 nanometers in transmission electron microscopy (TEM) pictures. The sulfamethoxazole ligand was shown to be bidentate coordinated to the metallic ions with sulfonyle oxygen and amido nitrogen groups, according to IR spectral data. Both Ru(III) and Au(III) complexes have an electrolytic nature, but the Pt(IV) complex has non-electrolytic properties. TG and DTG experiments proved the assigned composition and provided information regarding the thermal stability of complexes in a dynamic air atmosphere, according to the thermal analysis. The effect of the novel prepared complexes was examined for antibacterial and antifungal activity in vitro against a variety of pathogens, and they exceeded the sulfamethoxazole ligand in antibacterial activity. It was observed that the Pt(IV) complex has the ultimate activity versus all the assessed organisms relative to all compounds.

Magnetic properties of rare-earth zigzag chain systems RAgSe2 (R = Ho, Er, Tm, and Yb)

In an antiferromagnetic zigzag chain, competition between the nearest and next-nearest neighbor interactions could give rise to magnetic frustration. Magnetic semiconductors RAgSe2 (R = Ho, Er, Tm, and Yb) crystallize in the ErAgSe2-type orthorhombic structure, where the R ions form a zigzag chain along the orthorhombic a-axis. The magnetic susceptibility data for all the samples follow the Curie-Weiss law between 40 and 300 K. The values of the effective magnetic moment μ βα are close to those expected for the free R 3+ ions. Negative values of the paramagnetic Curie temperature θρ indicate antiferromagnetic interactions. For R = Ho and Tm, the specific heat C(T) data exhibit no anomaly down to 0.4 K, which is ascribed to the nonmagnetic singlet ground states under the crystalline electric fields. On the other hand, for R = Er, C(T) shows peaks at T 1 = 1.3 K and T2 = 0.9 K, indicating successive antiferromagnetic transitions. For R = Yb, C(T) shows a lambda-type anomaly at T m = 1.8 K. The magnetic entropy at T m is only 30% of Rln2 expected for the ground state doublet, suggesting magnetic fluctuations above T m.

Local magnetic moment formation and Kondo screening in the half-filled single-band Hubbard model

We study the formation of local magnetic moments in the strongly correlated Hubbard model within dynamical mean-field theory and associate peculiarities of the temperature dependence of local charge ${\ensuremath{\chi}}_{c}$ and spin ${\ensuremath{\chi}}_{s}$ susceptibilities with different stages of local moment formation. The local maximum of the temperature dependence of the charge susceptibility ${\ensuremath{\chi}}_{c}$ is associated with the beginning of local magnetic moment formation, while the minimum of the susceptibility ${\ensuremath{\chi}}_{c}$ and double occupation, as well as the low-temperature boundary of the plateau of the effective local magnetic moment ${\ensuremath{\mu}}_{\mathrm{eff}}^{2}=T{\ensuremath{\chi}}_{s}$ temperature dependence are connected with the full formation of local moments. We also obtain the interaction dependence of the Kondo temperature ${T}_{K}$, which is compared to the fingerprint criterion of Chalupa et al. [Phys. Rev. Lett. 126, 056403 (2021)]. Near the Mott transition the two criteria coincide, while further away from the Mott transition the fingerprint criterion somewhat overestimates the Kondo temperature. The relation of the observed features to the behavior of eigenvectors/eigenvalues of fermionic frequency-resolved charge susceptibility and divergences of irreducible vertices is discussed.

Study of Magnetic Properties and Relaxation Time of Nanoparticle Fe3O4-SiO2.

The magnetic properties and relaxation time of Fe3O4 nanoparticles, and their encapsulation with silicon dioxide (Fe3O4-SiO2), have been successfully investigated by analyzing the temperature dependence of magnetization (()) and the time dependence of magnetization (()), using the SQUID magnetometer measurement. The () measurement results can determine the magnetic parameters and magnetic irreversibility of Fe3O4 and Fe3O4-SiO2 samples. The values of Curie constant (), effective magnetic moment (), and Weiss temperature () are 4.2 (emu.K.Oe/mol), 5.77 , and −349 K, respectively, for the Fe3O4 samples, and 81.3 (emu.K.Oe/mol), 25.49 , and −2440 K, respectively, for the Fe3O4-SiO2 samples. After encapsulation, the broadening peak deviation decreased from 281.6 K to 279 K, indicating that the superparamagnetic interactions increased with the encapsulation process. The magnetic parameters and irreversibility values showed that the superparamagnetic properties increased significantly after encapsulation (Fe3O4-SiO2). From the results of the () measurement, it was found that there was a decrease in the magnetic relaxation time after the encapsulation process, which indicated that the distribution of the nanoparticle size and anisotropy energy increased.

Tunable magnetocaloric effect at approximately room temperature by Y-substitution in Ho2Fe17

The structure, magnetic transition and magnetocaloric effect of the intermetallic compounds (Ho2-xYx)Fe17 (x = 0, 0.5, 1 and 1.5) were investigated. The compounds crystallize into a Th2Ni17-type structure with the P63/mmc space group, as determined by Rietveld refinement of the XRD powder diffraction patterns. All the samples undergo a second-order magnetic transition from the ferromagnetic to paramagnetic state, and the Curie temperature decreases from 334 K (x = 0) to 314 K (x = 1.5) with increasing Y content. In the paramagnetic region, the reciprocal magnetic susceptibilities χ−1 for (Ho2-xYx)Fe17 (x = 0.5, 1 and 1.5) obey the Curie-Weiss law. The effective magnetic moment was determined to be 28.97 μB/f.u., 32.88 μB/f.u. and 33.78 μB/f.u., respectively, with corresponding paramagnetic Curie temperatures of 323 K, 308 K and 304 K. The maximum magnetic entropy changes for (Ho2-xYx)Fe17 (x = 0, 0.5, 1 and 1.5) are 3.0 J/kg K, 3.5 J/kg K, 3.8 J/kg K and 4.6 J/kg K, with corresponding refrigerant capacity values of 168 J/kg, 197 J/kg, 263 J/kg and 342 J/kg for a field change of 0–5 T. The tunable Curie temperature and considerable magnetocaloric effect indicate that (Ho2-xYx)Fe17 (x = 0, 0.5, 1 and 1.5) compounds are candidates for room-temperature magnetic refrigerants.

Effect of Gd-doping in Ni/NiO core/shell magnetic nanoparticles (MNPs) on structural, magnetic, and hydrogen evolution reaction.

In this study, Gdx-doped Ni/NiO MNPs (x: 0.0%, 2.5%, 5.0%, and 10.0%) with a protective polyvinylpyrrolidone (PVP) layer have been synthesized via a polyol reduction process. The x-ray diffraction patterns revealed that samples have a cubic structure with Fm3̄m space group and no change in the crystallite structure was observed with doping Gd3+ ions. The crystallite size (Dc) decreases from 2.70 to 1.27nm when Gd is doped into Ni/NiO MNPs. Transmission electron microscopy analysis revealed that the Ni/NiO MNPs with Gd(5%) concentration are formed as spherical multicore-like shape core/shell MNPs with a protective PVP layer. The magnetic hysteresis measurements taken at 10 and 300K show that the saturation magnetization (Ms) decreases with increasing Gd3+ ions in the structure. The highest effective magnetic moment (μeff) was obtained as 10.34μB in the NG-2 sample. We ascribe that the high μeff value in this sample is due to the increase in d-f exchange interaction between Ni(3d7) and Gd(4f7) and the contribution of the dipole moment of PVP molecules. The electrochemical measurements showed that the current density values were 0.294 and 0.319 mA/cm2 at-1.3V in the absence of Gd (NG-0) and Gd(5%) doped (NG-2) samples, respectively. βc was 159 and 132 mV/dec for NG-0 and NG-2 samples, respectively. The diminishing of βc and the charge resistance (Rct) proved that the Gd doped catalyst enhanced the hydrogen evolution activity and the Gd(5%) doped sample exhibited the highest catalyst performance.

Magnetic Ground State and Tunable Néel Temperature in the Spin ½ Linear Chain Antiferromagnet Co(OH)(2−x)Fx

The ground state of Co2+ in the octahedral CoO6 crystal field has often been assumed to be in high spin state with S = 3/2. As a result, the effective magnetic moments of Co2+ are overestimated in Co(OH)(2−x)F x . Herein, it is argued that the ground state of Co2+ in Co(OH)(2−x)F x has effective spin 1/2 but not S = 3/2, due to spin–orbit coupling in distorted octahedral crystal field. Analysis of the published magnetic susceptibility (χ) data on three samples of Co(OH)(2−x)F x is reported here with the new result that the Néel temperature T N decreases with an increase in χ as T N = 36.5, 30.5, and 26.5 K are determined for x = 1.09, 1.14, and 1.26, respectively. The employment of modified Curie–Weiss (CW) law along with S = 1/2 ground state eliminates the reported disagreement between the magnetic moment μ(Co2+) obtained from CW law above and neutron powder diffraction (NPD) below The fits of the data to the predictions of the linear chain model yield the exchange constant J/k B = −30.5, −28.1, and −24.7 K for x = 1.09, 1.14, and 1.26, respectively, supporting the chain‐like antiferromagnetic ordering observed using NPD.

SYNTHESIS, CHARACTERIZATION AND ANTIMICROBIAL STUDIES OF 3-BROMOBENZALDEHYDE NICOTINIC ACID HYDRAZONE AND IT’S Co(II), Cu(II), Mn(II) AND Ni(II) COMPLEXES

Acyl hydarazones and other hydrazones derivatives are of immense biological importance as a result of their antibacterial, antifungal, antiinflammatory properties and coordination Chemistry. The ligand was prepared by refluxing nicotinic acid hydrazide and 3-bromobenzaldehyde in ethanol, the complexes were synthezed by mixing ethanolic solutions of the metal salts with the hydrazone. The ligand and complexes were characterized on the basis of uv-visible, FTIR, melting point, conductivity, magnetic susceptibility, metal analysis and mole ratio, antimicrobial activities were determined. The ligand and complexes formed are high melting point crystalline solids. Thermodynamic stability study showed that the complexes are stable with stability constants between 2.84 x 105 – 2.21 x 107 while the solution studies gave 1:2 metal to ligand ratio. Infrared spectra data are diagnostic of bidentate coordination of the ligand via carbonyl oxygen and azomethine nitrogen atoms as result of the negative shift in the (C=O) and (C=N) bands. Effective magnetic moment of the complexes is 5.62 B.M, 4.02 B.M. and 1.81 B.M. for Manganese, Cobalt and Copper complexes respectively, the nickel complex is diamagnetic. Electronic spectra of the ligand indicate n * transitions, transition in the manganese complex is spin and orbital forbidden with very low molar absorptivity, nickel complex gave two bands assigned to 3A2g(F) 3T1g(F) and 3A2g(F) 3T1g(P) transition, cobalt complex gave one electronic band assigned to 4T1g(F) 4A2g transition. Copper complex gave one band, assigned to 2Eg 2T2g transition. On the basis of magnetic and electronic spectral of the isolated complexes octahedral geometry has been proposed for the Mn(II), Co(II) and Cu(II) complexes and square planar for the Ni(II) complex. The activities of the complexes against most of the microorganisms were enhanced compared to those of their parent ligand, with some promising potential when compared to the control drugs.

Electrical and magnetic properties of intercalated compounds in the Gd-=SUB=-x-=/SUB=-NbSe-=SUB=-2-=/SUB=- system (0≤ x≤0.33)

The electrical and magnetic properties were measured on polycrystalline samples of niobium diselenide intercalated with gadolinium atoms. The dependences of the electrical resistance on temperature point to a predominantly phonon scattering mechanism for charge carriers, while the concentration dependences are determined by increasing scattering by interstitial atoms. The magnetic properties of GdxNbSe2 (0≤ x≤0.33) were studied in the temperature range of 2-350 K and in the range of magnetic fields up to 70 kOe. Based on the results of studies of magnetic susceptibility and magnetization, the possibility of the existence of antiferromagnetic interactions in the studied compounds and the phenomenon of spin reorientation in a magnetic field are shown. The observed decrease in the effective magnetic moment of gadolinium ions with an increase with their concentration is discussed in terms of a possible intramolecular exchange. Keywords: niobium diselenide, gadolinium, intercalation, electrical resistance, magnetization, effective magnetic moment.

Anisotropic thermal expansion and electronic transitions in the Co3BO5 ludwigite.

The investigations of the crystal structure, magnetic and electronic properties of Co3BO5 at high temperatures were carried out using powder X-ray diffraction, magnetic susceptibility, electrical resistivity, and thermopower measurements. The orthorhombic symmetry (Sp.gr. Pbam) was observed at 300 K and no evidence of structural phase transitions was found up to 1000 K. The compound shows a strong anisotropy of the thermal expansion. A large negative thermal expansion along the a-axis is observed over a wide temperature range (T = 300-600 K) with αa = -35 M K-1 at T = 500 K with simultaneous expansion along the b- and c-axes with αb = 70 M K-1 and αc = 110 M K-1, respectively. The mechanisms of thermal expansion are explored by structural analysis. The activation energy of the conductivity decreases significantly above 700 K. Electronic transport was found to be a dominant conduction mechanism in the entire temperature range. The correlations between the thermal expansion, electrical resistivity, and effective magnetic moment were revealed and attributed to the evolution of the spin state of Co3+ ions towards the spin crossover and gradual charge-ordering transition.

Regulation of the electronic structure of perovskites to improve the electrocatalytic performance for the nitrogen-reduction reaction

The correlation between the effective spin magnetic moment of Co-doped LaNiO3 and its catalytic performance for the electrocatalytic nitrogen reduction reaction.

PHYSICO-CHEMICAL CHARACTERISTICS OF MATERIALS BASED ON CERIUM AND CHROMIUM LANTHANOIDES

Some physical and chemical characteristics of hexa(thiocyanate-N)chromate complexes of cerium lanthanides with 3-pyridine-3-carboxylic acid are studied. It was shown by IR spectroscopy for displacement of the main absorption bands that the compounds are N-thiocyanate, the organic ligand is bidentate due to the proton transfer of the carboxyl group to atom nitrogen with the formation of a conjugate system: imino-amine tautomerism of organic ligand leads to the occurrence of pyridinium-3-carboxylic ion. It was established by X-ray diffraction analysis of monocrystals that substances have an isle structure, crystallize according the same structural type, and their crystallographic parameters change regularly in accordance with the change in the radii of Ln3+ ions. The obtained substances of the isle type are isostructural. Iintermolecular hydrogen bonds between crystallization water molecules and N–H groups of coordinated molecules of organic ligands are found. The compositions of the substances differ only in the content of crystallization water in the molecules. Studies of the magnetic properties of the samples were carried out taking into account their stability in the range of 80-360 K. The decomposition sequence is established and composition of thermolysis products. The experimental and calculated values effective magnetic moments is in agreement. Values effective magnetic moments characterize the antiferromagnetic nature of the interaction between paramagnetic centers. At temperatures below 100 K, discrepancies between the experimental and calculated values are observed, which may be due to the transition of compounds from the paramagnetic to antiferromagnetic state. The thermal behavior of substances in an inert atmosphere and oxidizing atmospheres to interval of tempetures 293-1273 K are presented. Compounds obtained determine the promising magnetic and thermal properties of substances as precursors for the low-temperature production of heterometallic oxide ceramic materials, as well as molecular magnets and thermoindicators for visual control of temperatures and temperature fields.

Electrical and magnetic properties of vanadium diselenide intercalated with chromium atoms

The study of the structural characteristics, electrical and magnetic properties was carried out on synthesized samples of vanadium diselenide intercalated with chromium atoms. Structural studies have shown a decrease in the symmetry of the crystal lattice from hexagonal to monoclinic with an increase in the concentration of intercalated atoms, caused by their ordering in the Van der Waals gap. In this case, a change in the resistive state occurs in samples of different compositions, which are characterized by opposite thermal coefficients of electrical resistance. The values of the effective magnetic moments of chromium ions in CrxVSe2 decrease in comparison with the spin characteristics with an increase in the chromium content and their change correlate with the concentration dependence of the parameter c of the unit cell. At low temperatures for compositions x>0.2, the compounds undergo a transition to the state of a spin glass with a critical temperature of up to 30 K. Keywords: vanadium diselenide, chromium, intercalation, electrical resistance, magnetic susceptibility, spin glass.