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1.
Low temperature Mössbauer spectra and magnetic ordering of lithiated ferric molybdate: Li2Fe2(MoO4)3
Powder x-ray diffraction, variable temperature magnetic susceptibility, and zero field Mössbauer spectroscopy measurements were used to characterize the new phase Li2Fe2 (MoO4)3. This material is obtained topochemically simply by the mixing of solutions of lithium iodide in acetonitrile with solid Fe2(MoO4)3 at ambient temperature. Li2Fe2(MoO4)3 possesses the high temperature orthorhombic ferric molybdate $$\begin{gathered} Fe_2 (MoO_4 )_3 + 2LiI\xrightarrow{{CH_3 CN}}Li_2 Fe_2 (MoO_4 )_3 + I_2 \hfill \\ (solid)(solution)(solid)(solution) \hfill \\ \end{gathered}$$ structure. Guinier photographs were completely indexed in space group Pnca. Magnetic hyperfine splitting of the zero field Mössbauer spectrum below 12.5 K indicates a three-dimensional magnetically ordered state which susceptibility results show to be weakly ferromagnetic owing to probable canting of antiferromagnetically coupled sublattices. 相似文献
2.
Zero field Mössbauer spectra and powder susceptibility measurements show that the condensed, hydrogen bonded network compound FeSO3 3H2O orders antiferromagnetically (TNéel 9.5 K). The related anhydrous material FeSO3 also shows antiferromagnetic exchange but no evidence of long range three-dimenstional magnetic order to as low as 1.4 K.Supported by the U.S. National Science Foundation Division of Materials Research—Solid State Chemistry Program Grant No. DMR 8313710. 相似文献
3.
Reactions of ferrocene (C5H5)2Fe with halogenated fullerenes C60X
n
for X=F, Cl, Br andn = 15–39) yield non-stoichiometric solids with intense singlet Mössbauer spectra characteristic of Cp2Fe+ (where Cp=C5H5). The material isolated from reaction of Cp2Fe with C60Br24 exhibits two different iron environments and magnetic ordering temperatures of 14 K and between 4.6 and 1.32 K. These data are seen to be consistent with loss of bromine from the fullerene and formation of ferricenium tetrahaloferrate salts. 相似文献
4.
Monocationic forms of the symmetric and asymmetric indacene bridged species [(Cp*Fe)2(-s-indacene)],I, and [(Cp*Fe)2(-as-indacene)],II, are fully detrapped and trapped, respectively, over the entire range from 1.5 K to ambient temperature as their BF
4
–
salts. In contrast to [II
+][BF
4
–
], the TCNE.– salt [II
+][TCNE.–] exhibits a transition from fully trapped to a largely detrapped valence state behaviour over the increasing temperature range 100 to 300 K. Mössbauer spectra ofI suggest that while it is relatively insensitive to oxygen as a neat solid, it is strongly oxidized by O2 in dry hexane solution. Similar studies ofII indicate essential insensitivity to O2, both as a solid and in hexane solution. 相似文献
5.
W. M. Reiff B. D. James M. Bakalova J. Liesegang A. H. White B. W. Skelton D. C. R. Hockless 《Hyperfine Interactions》1994,94(1):2081-2086
Iron-57 Mössbauer spectroscopic results for a new series of related chloroferrate salts of complex ammonium cations are presented. In particular, spectra of materials based on FeCl
4
–
, FeCl
5
2–
, FeCl
6
–
, [FeCl5(H2O)]2–, and [FeCl5(CH3OH)]2– anions are discussed relative to the systematics of their isomer shifts, coordination numbers, and low temperature 3D critical ordering temperatures. The following specific systems have been studied by Mössbauer spectroscopy and definitively characterized by single-crystal X-ray analysis: [CH3NH
3
+
]4[FeCl6]3–[Cl–](A), [Me2N(-CH2CH2)2NMe
2
+
][FeCl
5
2–
] (B), [H3NCH2CH2NH
3
2+
][FeCl5·H2O2–], (C), and [NH3(CH2)6NH
3
2+
]4[(FeCl
6
3–
)(FeCl
4
–
)ClCl
4
–
] (D). The spectral data for these complexes are considered in the light of results of previous studies for systems such as [K2FeCl5·H2O], [Co(NH3)6][FeCl6], diamethyltriethylenediammoniumpentachloroferrate (E), and the related [FeCl5·CH3OH]2– salt (F). The critical 3D ordering temperatures are 1.45, 6.80, 3.45, and 1.22K forA, B, C, andD, respectively. 相似文献
6.
7.
Poly[(2,2'-bipyridine)tetrakis(imidazolato)diiron(II)] was synthesized by the reaction of ferrocene with imidazole in an excess of 2,2'- bipyridine in a Carius tube at 130 degrees C. Dc magnetic susceptibility studies at an applied field of 1000 G reveal that on cooling from room temperature, the material undergoes two structural phase transitions designated alpha --> beta and beta --> gamma at 151 and 133 K, respectively. On warming, the gamma --> beta and beta --> alpha transitions are observed at 137 and 151 K, respectively; a 4 K thermal hysteresis clearly detectable in the lower temperature beta <--> gamma transition. These structural phase transitions have also been studied by detailed, variable-temperature, ac susceptibility and M?ssbauer spectroscopy techniques. Single-crystal X-ray diffraction studies done at 294, 143, and 113 K reveal 2, 12, and 6 unique iron centers in the alpha-, beta-, and gamma-forms, respectively. All three forms have the same basic structure involving 2D extended double layer sheets (bilayers) of alternating tetrahedral and octahedral irons singly bridged by imidazolate ligands, with the octahedral centers additionally coordinated by 2,2'-bipyridine ligands that occupy positions between the sheets. Magnetic susceptibility and bond length data reveal that in the gamma-phase one in three six-coordinate sites corresponds to spin singlet ground-state iron(II); i.e., the overall alpha --> gamma process involves a spin-crossover transition such that at least 1/6 of the iron sites in the gamma-phase correspond to S = 0. This is supported by the low-temperature M?ssbauer spectra of the gamma-phase, which reveal the simultaneous presence of both S = 2 and S = 0 iron(II) centers. The compound magnetically orders, with a resultant small remnant magnetization, at low temperatures. The magnetic phase transition, studied by a combination of dc and ac susceptibility and M?ssbauer techniques, occurs at T(c) approximately 6.5 K. 相似文献
8.
Zero-field Mössbauer spectra of powder samples of Fe(2,9-di-CH3-phenanthroline) SO4 over the range 1.7 to 300°K show a large (~ 3.6 mm/sec) temperature-independent quadrupole splitting corresponding to an orbital singlet ground term. The chemical isomer shift, δFE=O, is 1.16 mm/sec (source and absorber at 4.2°K) corresponding to six coordinate high-spin iron (II). Below 4.2°K, the compound exhibits magnetic hyperfine splitting suggesting slow relaxation and the possibility of long-range three-dimensional magnetic ordering with a critical temperature Tc such that 3.5°K < Tc < 4.2°K and an internal hyperfine field Hn = 325 kG at 1.69°K. High-field Mössbauer spectra at 300°K indicate that the principal component of the electric field gradient tensor is positive and axial. Similar spectra at 4.2°K show an absence of nuclear Zeeman splitting for applied fields up to 60 kG, and indicate that at 4.2°K the material is rapidly relaxing but with substantial magnetic polarization and a negative internal hyperfine field. The temperature dependence of the magnetic susceptibility confirms antiferromagnetic interactions with a broad maximum χ′M at ~ 11.8°K presumably due to low-dimensionality exchange interactions (possibly one) along MOSOM chains. Least-squares fits of χ′M?1 versus T for T50°K indicate (Curie-Weiss behavior with C = 3.26 emu/mole, θ = -21.95°K, and μeff = 5.11. 相似文献
9.
The origins of the extraordinarily large internal hyperfine field (62.4 T) for the three-dimensional (weak) ferromagnetically ordered ground state of alpha-Fe(OETAP) are discussed semiquantitatively in terms of existing physical theory. In particular, the classical Fermi-contact contribution to the internal field is found to be highly enhanced by a very large orbital contribution and a significant dipolar term of the same sign. A rationale for the unexpected ordering of this S = 1 non-Kramers system is also presented. 相似文献
10.
The extension of a new, low dose, Mössbauer spectroscopy approach to cancer radiation therapy to “easy” isotopes other than Iron-57 is outlined. New in vitro studies using a number of cancer cell lines are reported. 相似文献