Tetrahedral antiferromagnetism in Ni(BrO3)26H2O

The magnetic susceptibility of Ni(BrO₃)₂6H₂O was measured from 20 K down to 0.07 K. A sharp peak at 0.21 K interpreted as the onset of long range antiferromagnetic order of the tetrahedral type.     

Low temperature differential magnetization of Ni(ClO4)26NH3 and Ni(BF4)26NH3

The differential magnetization of Ni(ClO₄)₂6NH₃ and Ni(BF₄)₂6NH₃ was measured as a function of temperature (20 to 0.3 K) and magnetic field (up to 40kOe). An antiferromagnetic transition was found at T_N = 0.45 K for the Ni(ClO₄)₂6NH₃ and T_N = 0.43 K for the Ni(BF₄)₂6NH₃, and a portion of the magnetic phase diagram was determined. The interpretation of the data in terms of a uniaxial model yielded (D/k) ～ 0.2 K for both salts.     

Ni(C3H10N2)2NO2(ClO4)晶体的ESR研究

报道了Ni(C₃H₁₀N₂)₂NO₂(ClO₄)晶体在T=1.5K温度和W波段的ESR实验.建立了d⁸离子基态³A₂(F)的零场分裂参量D,E,和g因子与斜方对称晶场势参量间的关系,并应用于Ni(C₃H₁₀N₂)₂NO₂(ClO₄)晶体.计算值与实验数据符合很好,表明所给关系式是合理的.     

[Fe3O(Ala)6(H2O)3](ClO4)7和[Fe3O(Gly)6(H2O3)(NO3)7)·3H2O]顺磁共振谱及变温磁化率研究

本文通过对[Fe 3O(Ala) 6(H 2O) 3](ClO 4) 7和[Fe 3O(Gly) 6(H 2O) 3](NO 3) 7·3H 2O的ESR谱的解析及变温磁化率的研究,得出它们的ESR谱具有各向同性的特点;朗德因子分别为2.019和1.997;两种配合物中铁离子间有反铁磁相互作用.     

[Fe3O（Ala）6（H2O）3]（ClO4）7和[Fe3O（Gly）6（H2O）3]（NO3）7·3H2O的顺原共振谱及变温磁化率研究

本文通过对[Fe 3O(Ala) 6(H 2O) 3](ClO 4) 7和[Fe 3O(Gly) 6(H 2O) 3](NO 3) 7·3H 2O的ESR谱的解析及变温磁化率的研究,得出它们的ESR谱具有各向同性的特点;朗德因子分别为2.019和1.997;两种配合物中铁离子间有反铁磁相互作用.     

Proton ENDOR of VO(H2O)5 2+ in Mg(NH4)2(SO4)2)26H2O

ENDOR measurements at 25 K have been used to determine the hyperfine coupling tensors for all ten protons in the VO(H₂O)₅ ²⁺ ion in single crystals of Mg(NH₄)₂(SO₄)₂6H₂O. The traceless components of all the tensors are close to axial and their use in a point dipole treatment enables a very plausible geometrical model of the complex ion to be constructed. Six of the protons in the equatorial water molecules have substantial positive isotropic couplings and it is suggested that these reflect the direct admixture of hydrogen 1s components into the singly occupied orbital.     

ESR studies of Cl2- (VK) centre trapped in irradiated Ca(ClO3)2 . 2H2O single crystals

A Cl₂- centre has been trapped in X or γ-irradiated Ca(ClO₃)₂. 2H₂O single crystals at 298 K, when the irradiated crystals were illuminated with ultra-violet light (360 nm). This centre is formed at the expense of ClO₂ centres in this crystal. This Cl₂ ^- centre is trapped at two magnetically inequivalent sites in the crystal lattice and these sites become equivalent when the static magnetic field is parallel or perpendicular to the b axis. At many orientations this centre reveals ‘super-hyperfine’ interaction with a proton (I = 1/2) of the water of crystallization. The magnetic parameters are close to those observed in alkali chlorides and the E.S.R. spectrum has been fitted to an orthorhombic spin hamiltonian. The principal g values are g_xx = 2·035, g_yy = 2·033 and g_zz = 2·000 and those of the A values are A_xx = 15·0, A_yy = 31·0 and A_zz = 109·0 G. The shfs parameters are A _‖' = 5·0 A _⊥' = 1·0 G. The V_K centre trapped in this lattice is exceptionally stable at room temperature.     

EPR of Mn2+ doped in Zn(BF4)26H2O

EPR of Mn²⁺ doped (∼ 1%) in single crystal of zinc fluoroborate hexahydrate has been studied between 94 and 353 K. Angular variation study of the spectra indicated that the crystal field distortion has a trigonal symmetry along the crystallographic c-axis. The D distortion parameter has two linear regions in its thermal variation. It varies above 200 K as D = (149 + 0.107T)G and below 150 K as xzD = (127 + 0.228T)G. A “knee”-like curve links these two linear regions confirming an anomaly observed in a previous work at 181 K due to a phase transition. Other spin Hamiltonian parameters are g = 2.000 ± 0.001, a = (8.9 ± 1.5)G, A = (97.9 ± 0.9)G and B = (97.0 ± 0.9)G. They are constant with temperature.     

An ESR study of phase transitions in crystals of M(BF4)2·6H2O (M = Fe,Co, Ni,Zn)

From a temperature dependent ESR study of Mn²⁺-doped crystals of M(BF₄)₂·6H₂O, M Zn, Co and Ni, new structural phase transitions have been detected and studied. First order structural phase transitions occur in Co(BF₄)₂·6H₂O at T₁ ~ 281K, T₂~189 K and T₃~172K (during cooling), in Zn(BF₄)₂·6H₂O at T₁ ~ 286 K and in Ni(BF₄)₂·6H₂O at T₁ ~ 301 K. A continuous phase transition occurs in Co(BF₄)₂·6H₂O at T_p ~ 257 K, in Zn(BF₄)₂·6H₂O at T_p ~ 277 K and in Ni(BF₄)₂·6H₂O at T_p ~ 294 K. The ESR spectral characteristics suggest similarities in the structures of these fluoroborate compounds in the phase above T₁ with the room temperature structure of Mg(ClO₄)₂·6H₂O. All these compounds are found to have a tendency to crystallise in a triply-twinned pseudo-hexagonal form, although the unit cell above T₁ is found to be orthorhombic. The structural changes related to the water octahedron around the metal at T₁ were found to be very small and basically the same for these three compounds. Although the unit cell structure of Fe(BF₄)₂·6H₂O above the first order phase transition temperature T₁ was found to be similar to that of the other fluoroborate compounds, the structural changes occurring at T₁ appeared to be quite different. The low temperature thermal behaviour differs considerably in the Co, Fe and Zn compounds.     

ESR of Gamma Irradiated C2H204.2H2O Single Crystal

The gamma-irradiated samples of vacuumed powder and single crystal of C₂H₂O₄.2H₂O have been investigated by ESR method. the spectra of these single crystal and unvacuumed powder are attributed to R C HOH radical, but the peaks belonging to this radical in the gamma irradiated powder sample are not observed in the spectrum after having been vacuumed. After a and g tensor values of this radical have been calculated, it was observed to be anisotropic. At low temperature, a considerable change in the spectrum has not been observed.     

Kinematics of the reaction H2O+(H2,H)H3O+

The kinematics of the reaction H₂O⁺(H₂,H)H₃O⁺ were studied in crossed-beam experiments in the low collision-energy range 0.1–2 eV (c.m.). The scattering diagrams, center-of-mass angular distributions, and product relative translational energy distributions obtained show that the reaction proceeds predominantly by the impulsive, stripping mechanism. The translational exoergicity vs. collision energy plot obeys the spectator-stripping prediction.     

Low temperature studies on magnetic properties of Tm2O3

Magnetic properties of Tm₂O₃ were studied by means of magnetometry as well as by heat capacity measurements. The specific heat data were collected down to 0.35 K, and yielded some new information about crystal field splitting of the ³H₆ thulium multiplet. Some anomalous behaviour of the specific heat below 5 K was observed. It turned out, that this anomaly can be nicely described by Schottky contribution originating from crystal field levels distribution of the Tm³⁺ multiplet. No magnetic ordering was evidenced down to the lowest temperatures studied.     

Low temperature heat capacity of YBa2Cu3O7

We have measured the heat capacity of superconducting, single phase YBa₂Cu₃O₇ in the temperature range 2 to 18 K. An extrapolation of the data between 4 and 9 K gives aC/T (T → 0) of ∼ 25 mJ/mole K². The Debye temperature obtained from the high temperature linear portion ofC/T vsT ² plot is 325 K.     

Dynamics of H2O molecules in ferroelectric K4Fe(CN)6 · 3H2O

The infrared spectrum of potassium ferrocyanide trihydrate has been recorded both in the para and ferroelectric phases. From a combined study of the IR and Raman spectra, it is concluded that there are two sets of water molecules present in the lattice, one set being involved in stronger hydrogen bonding than the other. The ferroelectric transition appears to be associated with an ordering of the water dipoles.     

Chemical states of57Fe-atoms after ec-decay of57Co-labelled Co(BrO3)2·6H2O studied by coincidence Mössbauer spectroscopy

Two kinds of time differential Mössbauer spectra of⁵⁷Co-labelled Co(BrO₃)₂·6H₂O were measured at room temperature by delayed coincidence technique, i.e., one was the delayed coincidence between 122 keV γ ray and 14.4 keV γ ray (γ, γ-ray coincidence), and another was the coincidence between 6.3 keV KX ray and 14.4 keV γ ray (X, γ-ray coincidence). The time dependence of chemical states of⁵⁷Fe-species were observed on γ, γ-ray and X, γ-ray coincidence Mössbauer spectra. The relative area intensities of⁵⁷Fe(II) observed on the X, γ-ray coincidence spectra were larger than those on the γ, γ-ray coincidence spectra on every time windows.     

Protonic conductivity and lithium intercalation in a new iron hydroxyphosphate hydrate: (H3O)[Fe(H2O)]3[H8(PO4)6]·3H2O

A new hydroxonium iron phosphate, (H₃O)[Fe(H₂O)]₃[H₈(PO₄)₆]·3H₂O, was synthesized through a precipitation route by means of acidic media. The crystal structure was solved by X-ray powder diffraction. Electrochemical characterizations, performed on this compound, show reversible intercalation of lithium and substantial lithium diffusion. Protonic conductivity is observed in agreement with the simultaneous presence of H₂O, hydrated protons and OH groups in the large intersecting tunnels of this intersecting tunnel structure.     

Na0.15(H3O)0.2CoO2·wH2O的超导电性

最近发现的水合钴氧化物超导体在某些方面具有与高温超导体十分相似的性质.本文报道含有高浓度的水合氢离子的钴氧化物超导体的超导电性磁测量结果.通过对样品的M(H,T)的测量,得到了大致的H～T相图.最后还讨论了系统中可能存在的2D～3D转变.     

Magnetic studies on synthetic phosphoferrite Fe 3 2+ (H2O)3(PO4)2

Synthetic crystals of phosphoferrite were studied by Mössbauer spectroscopy for temperatures ranging from 4.2 to 17.5 K. The analysis of the behaviour of the hyperfine fields for the two unequivalent sites near the Néel temperature (17.4 K) allowed the determination of the critical exponent for each site as ₁=0.171 and ₂=0.314.