Temperature Dependence Of Magnetic Susceptibility Research Articles

Three Cyanide-Bridged Fe <sup>II</sup>-M <sup>II</sup> (M = Fe, Co and Mn) Complexes: Synthesis, Crystal Structures and Magnetic Properties

Three dinuclear cyanide-bridged complexes Fe II (PY 5 OMe 2 )CNM II (PY 5 OMe 2 )[OTf] 3 (M = Fe 1 , Co 2 , Mn 3 ; PY 5 OMe 2 = 2,6-bis-((2-pyridyl)methoxymethane)pyridine OTf = CF 3 SO 3- ) have been synthesized and characterized. Single-crystal diffraction analyses show these three dinuclear compounds are very similar in structure. And the M-N (M = Fe, Co and Mn) bond lengths for complexes 1 - 3 indicate that 2 and 3 are typical of a high spin (HS) complexes and 1 is evident a low spin (LS) Fe (II) complex at room temperature, confirmed by the temperature dependence of magnetic susceptibilities of complexes 1-3 . The different magnetic behaviors of complexes 1 - 3 reveal that in the three complexes all the cyanide-carbon coordinated Fe (II) are low-spin, and Co (II) for 2 and Mn (II) for 3 are both in a high-spin state through 2-400 K but the cyanide-nitrogen coordinated Fe (II) for complex 1 begins to occur a spin crossover (SCO) transition from 300 K.

Specific features of the electronic and crystal structure of CuxZrSe2 (0 < x ≤ 0.3)

Crystal and electronic structure, optical absorption and transmission spectra, temperature dependences of conductivity and magnetic susceptibility were studied for copper intercalated ZrSe2 in the copper concentration range of 0 ≤ x ≤ 0.3.

Physico-chemical properties of V1-XFeX O2 and FeV2O6

The article presents the results of a study of the heat capacity of V1-XFeXO2, temperatures of phase transformations in the semiconductor phase have been determined. The phase transition diagram of the V1-XFeXO2 system is presented. Values of the change in the entropy of phase transformations for V1-XFeXO2 materials are determined. It was determined that the values of the change in the entropy of the metal-semiconductor phase transition decrease with iron concentration increasing. The results of differential thermal analysis, temperature dependences of electrical resistivity, magnetic susceptibility, and thermoelectric coefficient are presented for the FeV2O6 compound. It was determined that the FeV2O6 compound is a semiconductor in the temperature range from 100 К up to 400 К.

Соединение HoFeTi-=SUB=-2-=/SUB=-O-=SUB=-7-=/SUB=-: cинтез, особенности кристаллической структуры и магнитные свойства

Polycrystalline HoFeTi2O7 samples were obtained by solid-phase synthesis and studied by X-ray diffraction, gamma resonance, and SQUID methods. The characteristics of structural properties are presented, indicating the distribution of iron atoms over nonequivalent crystallographic positions and their uneven filling in the positions mixed with titanium. Spin disorder formed by mixing magnetic and nonmagnetic ions, spatial inhomogeneity of interactions that determine the magnetic structure in the crystal leads to the formation of competing exchange magnetic interactions between the nearest neighbors, frustration of magnetic bonds and the absence of long-range magnetic order. It has been shown that the temperature dependence of the static magnetic susceptibility at low temperatures has features characteristic of the spin glass magnetic state.

Structure and magnetic properties of a serendipitously synthesized copper(II) complex: [Cu(3-Br-2-pyone)6](ClO4)2

Hexakis(3-bromo-2(1H)-pyridone)copper(II) perchlorate was prepared. Crystals and powdered bulk samples were characterized using IR, single-crystal and powder X-ray diffraction, combustion analysis, EPR and temperature-dependent magnetic susceptibility data. The complex crystallizes in the triclinic space group P$$\bar{1}$$ and comprises a Jahn–Teller distorted Cu(II)–O6 coordination sphere with the ligands coordinated via the pyridone O-atoms. EPR and variable temperature susceptibility measurements show that the complex is well isolated magnetically in the lattice.

Magnetism and spin-gap behaviour in the layered Pr3T4Al12 (T = Fe, Ru, Os) compounds with the distorted Kagomé lattice

We have investigated the physical and magnetic properties of the distorted Kagomé lattice structure compounds; PrAl12 (T = Fe, Ru, Os) which crystallize in the hexagonal Gd3Ru4Al12-type structure with space group P63/mmc (No. 194). The three compounds show long-range magnetic orderings of FM type at TC = 36.5 K (Fe), 39 K (Ru) and 37 K (Os) as indicated by the temperature dependences of magnetic susceptibility, , specific heat, Cp (T) and electrical resistivity, . Pr3Ru4Al12 shows an additional anomaly at 7 K which is associated to possible spin reorientation of some of the Pr moments. We also observed an additional anomaly in Pr3Fe4Al12 at 132 K which might be associated to the formation of a spin density wave. The Sommerfeld coefficient, extracted from Cp (T) in the temperature range immediately above TC indicate heavy fermion behaviours in PrAl12 (T = Fe, Ru, Os). of the three compounds show spin-gap behaviours below TC of comparable energy gaps magnitude.

Self‐Consistent Four‐Particle Cluster Model of Fe3+ Heisenberg Chains: Spectral and Magnetic Properties of YFe3(BO3)4 Crystals

The magnetic properties of antiferromagnetic quasi‐1D YFe3(BO3)4 crystals are studied based on the analysis of the measured optical spectra of the Fe3+ ions in different rare‐earth (RE) iron borates and a self‐consistent four‐particle cluster approach to helical iron chains. The parameters of crystal fields affecting the Fe3+ ions are calculated in the framework of the exchange charge model. The parameters of the isotropic intrachain and interchain exchange interactions between the Fe3+ ions are determined from modeling the temperature dependences of magnetic susceptibilities, the phase transition temperature, and spontaneous magnetic moments. The magnetic easy‐plane anisotropy is explained as the result of dipolar interactions between the Fe3+ ions in the trigonal crystal lattice. The developed model can be used to analyze and predict the properties of multiferroic multifunctional RE iron borates and highlight contributions of the iron subsystem into the magnetoelectric and magnetoelastic effects in these compounds.

1-(1,2,4-Triazol-3-yl)-1H-tetrazoles and their complexation with copper(II) chloride

1-(1,2,4-Triazol-3-yl)-1H-tetrazole (trt) and 1-(1-tert-butyl-1,2,4-triazol-3-yl)-1H-tetrazole (btrt) were synthesized by heterocyclization of corresponding amines with triethyl orthoformate and sodium azide. The interaction of trt with copper(II) chloride in ethanol in the presence of hydrochloric acid was found to result in 1D coordination polymer [CuCl2(trt)(H2O)]n·nH2O. N-tert-butylated ligand btrt reacts with the copper salt in ethanol giving 2D coordination polymer [CuCl2(btrt)]n. Tetrazole ring-opening reaction with the formation of [CuCl2(3-amino-1,2,4-triazolium)2][CuCl4]·2H2O was observed in the interaction of trt with copper(II) chloride in aqueous hydrochloric acid. The temperature-dependent magnetic susceptibility measurements of [CuCl2(btrt)]n revealed that the copper(II) ions were weakly ferromagnetically coupled showing a coupling constant J of 1.2 cm−1.

Simultaneous Spin-Crossover Transition and Conductivity Switching in a Dinuclear Iron(II) Coordination Compound Based on 7,7',8,8'-Tetracyano-p-quinodimethane.

The reaction of Fe(OAc)2 and Hbpypz with neutral TCNQ results in the formation of [Fe2 (bpypz)2 (TCNQ)2 ](TCNQ)2 (1), in which Hbpypz=3,5-bis(2-pyridyl)pyrazole and TCNQ=7,7',8,8'-tetracyano-p-quinodimethane. Crystal packing of 1 with uncoordinated TCNQ and π-π stacking of bpypz- ligands produces an extended two-dimensional supramolecular coordination assembly. Temperature dependence of the dc magnetic susceptibility and heat capacity measurements indicate that 1 undergoes an abrupt spin crossover (SCO) with thermal spin transition temperatures of 339 and 337 K for the heating and cooling modes, respectively, resulting in a thermal hysteresis of 2 K. Remarkably, the temperature dependence of dc electrical transport exhibits a transition that coincides with thermal SCO, demonstrating the thermally induced magnetic and electrical bistability of 1, strongly correlating magnetism with electrical conductivity. This outstanding feature leads to thermally induced simultaneous switching of magnetism and electrical conductivity and a magnetoresistance effect.

Magnetic ordering and specific features of its coexistence with superconductivity in Dy0.6Y0.4Rh3.85Ru0.15B4

The temperature dependences of dynamic magnetic susceptibility of a magnetic superconductor Dy0.6Y0.4Rh3.85Ru0.15B4 in a temperature range of 2–50 К and the field dependence of magnetization up to 6 T at fixed temperatures 2, 11, 18, and 50 K were studied for the first time. It is found that at ТFM = (21 ± 1) К there is a transition to the ferromagnetic state, and at Тc = (6.7 ± 0.1) К a transition to superconducting state is observed, which coexists with the ferromagnetic state in a broad range of temperatures of 2–6.7 K. It is suggested that there exists a triplet mechanism of superconducting coupling in Dy0.6Y0.4Rh3.85Ru0.15B4.

Magnetocaloric properties and critical behavior of Co2Cr1−xMnxAl Heusler alloys

We study the magnetocaloric effect and critical behavior of Co2Cr1−xMnxAl (x=0.25, 0.5, 0.75) Heusler alloys across the ferromagnetic (FM) transition temperature (TC). The Rietveld refinement of x-ray diffraction patterns exhibit a single phase cubic structure for all the samples. The temperature dependent magnetic susceptibility χ(T) data show a systematic enhancement in the Curie temperature and effective magnetic moment with the Mn concentration, which is consistent with the Slater–Pauling behavior. The M(H) isotherms also exhibit the FM ordering, and the analysis of χ(T) data indicates the nature of the phase transition to be a second order, which is further supported by scaling of the entropy curves and the Arrott plot. Interestingly, the Mn substitution causes an increase in the magnetic entropy change and, hence, a large relative cooling power for possible applications in multistage magnetic refrigerators. In order to understand the nature of the magnetic phase transition, we examine the critical exponents β, γ, δ for the x=0.75 sample by the modified Arrott plot and the critical isotherm analysis, which is further confirmed by the Kouvel-Fisher method and Widom scaling relation, respectively. The estimated values of β=0.507, γ=1.056, δ=3.084 are found to be close to the mean field theoretical values. The renormalized isotherms (m vs h) corresponding to these exponent values collapse into two branches, above and below TC that validates our analysis. Our results suggest the existence of long-range FM interactions, which decays slower than power law as J(r)∼r−4.5 for a three-dimensional mean-field theory.

Intermetallics of the types REPd3 X 2 and REPt3 X 2 (RE=La–Nd, Sm, Gd, Tb; X=In, Sn) with substructures featuring tin and In atoms in distorted square-planar coordination

Abstract The intermetallic compounds RET 3 X 2 (RE = La–Nd, Sm, Gd, Tb; T = Pd, Pt; X = In, Sn) have been synthesized from the elements by arc-melting and subsequent annealing sequences in tube or induction furnaces. The samples were characterized through Guinier powder diffraction patterns, and several structures were refined from single crystal X-ray diffractometer data. These indium and tin intermetallics crystallize with the orthorhombic CePd3In2-type structure, space group Pnma. The palladium (platinum) and indium (tin) atoms in the RET 3 X 2 structures build up complex three-dimensional [T 3 X 2] δ− polyanionic networks in which the rare earth atoms fill cavities. The striking structural motifs concern the indium, respectively tin substructures, in which part of the indium and tin atoms have distorted square planar homoatomic coordination environments: In1In12In22 units in PrPd3In2 with interatomic distances 325 pm In1–In1 and 332 pm In1–In2 as well as Sn1Sn12Sn22 units in PrPt3Sn2 with the larger distances of 356 pm for Sn1–Sn1 and of 344 pm for Sn1–Sn2. Temperature dependent magnetic susceptibility measurements have indicated Pauli paramagnetism or diamagnetism for the lanthanum compounds, van-Vleck paramagnetism for SmPt3In2 and Curie-Weiss paramagnetism for the remaining compounds. Antiferromagnetic ordering was detected at T N = 4.0(1) K for CePt3In2 and at T N = 3.5(1) K for SmPt3In2. CePt3In2 shows a metamagnetic transition at an external magnetic field of 47(3) kOe.

Superconductivity in Ru-doped CuIr2Te4 telluride chalcogenide

Here we report the effect of structural and superconductivity properties on Ru doped CuIr2Te4 telluride chalcogenide. XRD results suggest that the CuIr2-xRuxTe4 maintain the disordered trigonal structure with space group P3m1 (No. 164) for x less than 0.3. The lattice constants, a and c, both decrease with increasing Ru content. Temperature-dependent resistivity, magnetic susceptibility and specific-heat measurements are performed to characterize the superconducting properties systematically. Our results suggest that the optimal doping level for superconductivity in CuIr2-xRuxTe4 is x = 0.05, where Tc is 2.79 K with the Sommerfeld constant gamma of 11.52 mJ mol-1 K-2 and the specific-heat anomaly at the superconducting transition, is approximately 1.51, which is higher than the BCS value of 1.43, indicating CuIr1.95Ru0.05Te4 is a strongly electron-phonon coupled superconductor. The values of lower critical filed and upper critical field calculated from isothermal magnetization and magneto-transport measurements are 0.98 KOe and 2.47 KOe respectively, signifying that the compound is clearly a type-II superconductor. Finally, a dome-like shape superconducting Tcs vs. x content phase diagram is established, where the charge density wave disappears at x = 0.03 while superconducting transition temperature (Tc) rises until it reaches its peak at x = 0.05, then, with decreasing when x reaches 0.3. This feature of the competition between CDW and the superconductivity could be caused by tuning the Fermi surface and density of states with Ru chemical doping.

Syntheses, structures and properties of copper(II) and cobalt(II) complexes with 5(3)-amino-2-chloro-3(5)-methylpyridine isomer cations

New coordination compounds of copper(II) and cobalt(II) with 5-amino-2-chloro-3-methylpyridine (L1) and 3-amino-2-chloro-5-methylpyridine (L2) of the following composition: (HL1)2[CuCl4] (1), (HL1)2[CoCl4]·HCl·H2O (2), (HL2)2[CuCl4]·H2O (3), (HL2)2[CuCl4]·2H2O (4) and (HL2)2[CoCl4] (5), have been synthesized. In an acetone environment, L1 may undergo a Schiff condensation reaction and the product of its complexation [CuL1*Cl3] (6) was also obtained. The compounds have been investigated by single-crystal X-ray diffraction, simultaneous TG–DSC analysis, IR and diffuse reflectance spectroscopy, and temperature-dependent magnetic susceptibility measurements. Exchange interactions between the unpaired electrons of the metal ions have a different character depending on the composition of the complexes. For the Cu(II) compounds: 1, 2D-ferromagnetic layer, J = 13.53(15) K; 3, strong-rung ladder, Jrung = −7.26(1) K, Jrail = −1.87(2) K; 4, uniform chain, J = −4.1(1) K. The magnetic properties of the Co(II) compounds are dominated by single-ion anisotropy with D = −22(1) K (2) and −8.7(2) K (5). The copper(II) complexes show thermochromic behavior.

5,5,15,15-Tetraoxo-5,15-Dithiaporphyrin as a Highly Electron-Deficient Porphyrinic Ligand.

Oxidation of 5,15-dithiaporphyrin with meta-chloroperbenzoic acid afforded the corresponding S,S-tetraoxide in good yield. The resultant 5,5,15,15-tetraoxo-5,15-dithiaporphyrin exhibited the highly electron-deficient nature as elucidated by the electrochemical analysis and theoretical calculations. Treatment of tetraoxodithiaporphyrin with zinc(II) acetate and nickel(II) acetate provided the corresponding metal complexes efficiently. Owing to its enhanced Lewis acidity of the metal center by the electron-deficient ligand, the nickel complex underwent facile axial ligation to form pentacoordinate and hexacoordinate high-spin (S=1) complexes in solution and solid, respectively. The binding constant of pyridine to the NiII center was significantly higher than those of conventional porphyrin NiII complexes. Temperature-dependent magnetic susceptibility measurements of the high-spin NiII complex revealed the presence of weak ferromagnetic interactions.

Squares of gold atoms and linear infinite chains of Cd atoms as building units in the intermetallic phases REAu4Cd2 (RE=La–Nd, Sm) with YbAl4Mo2-type structure

Abstract The gold-rich intermetallic compounds REAu4Cd2 (RE = La–Nd, Sm) were synthesized from the elements in sealed tantalum ampoules. Their characterization by X-ray powder and single crystal data confirmed the tetragonal YbAl4Mo2 type, space group I4/mmm. The basic building units are Au4 squares (278 pm Au–Au in CeAu4Cd2) and infinite linear cadmium chains (275 pm Cd–Cd in CeAu4Cd2). We exemplarily studied the solid solution CeAu4+ x Cd2− x for x = 0–1 up to CeAu5Cd. Electron diffraction patterns on a CeAu5Cd sample confirm the single crystal data. They give no hint for complete gold-cadmium ordering. Temperature-dependent magnetic susceptibility measurements of CeAu4Cd2, CeAu5Cd, PrAu4Cd2 and NdAu4Cd2 show stable trivalent rare earth ions and give no hint for magnetic ordering above 3 K.

The Impurity Magnetic Susceptibility of Semiconductors in the Case of Direct Exchange Interaction in the Ising Model

The numerical simulation was applied to study the temperature dependence of the impurity magnetic susceptibility. The direct exchange interaction of the impurity magnetic moments randomly distributed in space was considered within the Ising model. When the temperature in a system decreases, the magnetic susceptibility behavior in this system ceases to comply with the Curie law, which is associated with the formation of a spin glass phase. It is shown that the expression of the preexponential factor in the formula for the direct exchange interaction considerably influences the temperature dependence of the magnetic susceptibility only in the case of ferromagnetic exchange.

Unconventional critical behavior in the quasi-one-dimensional S=1 chain NiTe2O5

Here we report a new quasi-one-dimensional $S$ = 1 chain compound NiTe$_{2}$O$_{5}$. From the comprehensive study of the structure and magnetic properties on high quality single crystalline NiTe$_{2}$O$_{5}$, it's revealed that NiTe$_{2}$O$_{5}$ undergoes a transition into an intriguing long-range antiferromagnetic order at $T_{\rm N}=30.5 {\rm K}$, in which longitudinal magnetic moments along the chain direction are ferromagnetically ordered, while their transverse components have an alternating ferromagnetic-antiferromagnetic coupling. Even though the temperature dependence of magnetic susceptibility represents an archetypal anisotropic antiferromagnetic order, we found that critical behavior of unconventional nature with $\alpha'\sim0.25$ and $\beta\sim0.18$ is accompanied by the temperature evolution of the antiferromagnetic order parameter.

Structures and Spectral and Magnetic Properties of a Series of Carbacylamidophosphate Pentanuclear Lanthanide(III) Hydroxo Complexes.

A series of pentanuclear lanthanide complexes Ln5L6(μ-L)4(μ3-OH)4(μ4-OH) (LnIII = Nd, Dy, Ho, Er, Yb; L- = dimethyl N-benzoylamidophosphate ion, [C6H5C(O)-N-P(O)(OCH3)2]-) was obtained by the reaction of sodium dimethyl N-benzoylamidophosphate with the corresponding lanthanide nitrates. The pentanuclear cores formed as a result of self-arrangement and their composition did not depend on the lanthanide ion. The complexes and sodium dimethyl N-benzoylamidophosphate have been characterized by single-crystal X-ray diffraction. The absorption spectra of the complexes were measured at 300 and 4 K. The dysprosium and ytterbium complexes exhibited weak emission in the visible and IR regions, respectively. Temperature dependences of magnetic susceptibility (χM) of the dysprosium, holmium, and erbium compounds were studied. It was found that χM vs T dependences were governed by the crystal field splitting effects with the Δ parameter being in the range 5-17 cm-1. Slow magnetic relaxation was found for the dysprosium complex by ac magnetic measurements, while no significant out-of-phase signals were detected for holmium and erbium complexes.

A Series of 3D Porous Lanthanide-Substituted Polyoxometalate Frameworks Based on Rare Hexadecahedral {Ln6W8O28} Heterometallic Cage-Shaped Clusters.

A series of 3D porous lanthanide-substituted polyoxometalate frameworks, Na2[Ln2(H2O)11]2[Ln3(H2O)3(α-SiW11O39)2]2·69H2O (1-Ln, Ln = Sm, Eu, Gd, Tb, and Dy), are built from novel hexadecahedral {Ln6W8O28} heterometallic cage-shaped clusters. Intriguingly, every tetrameric {[Ln3(H2O)3(α-SiW11O39)2]2}14- cage-cluster is linked with another eight tetrameric cage-clusters by Ln3+ cations, leading to a novel 3D inorganic porous framework, which exhibits good thermal and chemical stability, excellent water vapor adsorption capacity, and moderate proton conductive properties. Furthermore, the solid state luminescence spectra demonstrate that 1-Sm, 1-Eu, 1-Tb, and 1-Dy display the lanthanide characteristic emission bands. The temperature-dependent magnetic susceptibility indicates that there are antiferromagnetic interactions in 1-Tb and 1-Dy.