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  • 1
    Electronic Resource
    Electronic Resource
    Low-temperature magnetic properties of the 2D molecular ferrimagnet N(n-C5H11)4 [FeIIFeIII(C2O4)3] (1999)
    Springer
    JETP letters 70 (1999), S. 697-701 
    Details
    ISSN: 1090-6487
    Keywords: 76.80.+y ; 75.50.Gg ; 75.60.Ej
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract 57Fe Mössbauer and magnetometric studies of the molecular ferrimagnet N(n-C5H11)4 [ FeIIFeIII(C2O4)3] are indicative of a 2D magnetic character with strong uniaxial anisotropy in the basal plane of the crystal. It is established that the change in the sign of the net magnetization of this compound is related to a compensation between FeIII and FeII sublattice magnetizations at T comp=31.2 K. The form and parameters of the magnetic Hamiltonian describing the temperature dependence of the FeIII sublattice and the net magnetizations are determined.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1134/1.568248
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  • 2
    Electronic Resource
    Electronic Resource
    Synthesis, structure, and properties of a new trinuclear iron cluster, [(MeOH)(H2O)2Fe3(μ3-O)(μ-OOCC6H4OCH2C5H4NH)6] (ClO4)7 · · 8MeOH · 3.5H2O (1996)
    Springer
    Russian chemical bulletin 45 (1996), S. 1981-1987 
    Details
    ISSN: 1573-9171
    Keywords: trinuclear iron carboxylate complexes ; synthesis ; X-ray structural analysis ; spectroscopy ; cyclic voltammetry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Reactions of iron(m) salts with a new bidentate ligand, which is potentially capable of forming binuclear iron complexes upon complexation, were studied. Under various conditions, we succeeded in isolating only the trinuclear cationic complex (FeIII 3(O2CR)6(μ3-)17+ (1), where RCO2 is 2-(pyrid-2-ylmethoxy)benzoic acid protonated at the pyridyl moiety. The structure of 1 was established by spectral, magnetic, and X-ray structural studies. Cyclic voltammetry in McCN in the temperature range from -35 to 20 °C demonstrated that 1 undergoes successive FeIII→FeII reduction in three one-electron stages, which is indicative of the electronic interaction between iron atoms in the complex.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01457792
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  • 3
    Electronic Resource
    Electronic Resource
    Synthesis of molecular ferromagnetics [R3R′X]MCr(C2O4)3 (X = N, R = Bun, R′ = Prn, Et, Me; X = P, R = Ph, R′ = Bun; M = Mn, Fe, Co, Ni, Cu) (1996)
    Springer
    Russian chemical bulletin 45 (1996), S. 2210-2212 
    Details
    ISSN: 1573-9171
    Keywords: tris(oxalato)chromates(iii), synthesis ; molecular ferromagnetics, temperature of the transition to a ferromagnetic state
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The synthesis, IR spectra, and the temperatures of the transition into a ferromagnetic state (T c) of layered ferromagnetics [R3R′X[MCr(C2O4)3 (M = Mn, Fe, Co, Cu, and Ni) with the [Ph3BuP]+, [Bu3R′N]+ (R′ = Pr, Et, and Me) cations capable of subsequently changing the distances between metallooxalate layers have been considered. The temperatureT c has been found to be independent of the size of the organic cation. It is believed that the determining factors in the transition to a ferromagnetic state are exchange interactions inside the metallooxalate layer.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01430743
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  • 4
    Electronic Resource
    Electronic Resource
    Supertransferred hyperfine interaction in magnetic insulators (II) (1977)
    Springer
    Hyperfine interactions 5 (1977), S. 13-26 
    Details
    ISSN: 1572-9540
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The important mechanisms of supertransferred hyperfine (STHF) interactions in N−O−M chains are briefly discussed: (i) spin polarization ofns states in the N-ion due to the s-d exchange interaction,H STHF sd ; (ii) contributions of spin-polarized states of the intervening O-ion,H STHF II ; (iii) transfer of d-electrons of the M-ion to emptyns states in the N-ion,H STHF III . The dependence ofH STHF upon the N−O−M bond configuration, electronic structure, and orbital state of the M-ion is presented in a convenient form. The STHF interactions in the chains Sn4+−O2−−Fe3+, Cr3+ in compounds with slightly distorted Perovskite structure are considered. The STHF field in the chain Sn4+−O2−−Cr3+ is shown to change the sign within the range of angles near 170°. This conclusion is in line with published data on the isoelectronic chain Sn4+−O2−Mn4+ in the compounds Ca1−x Sr x MnO3. The results obtained for the N−O−Fe3+ chain are rationalized by the predicted angular dependence ofH STHF=α+β cos θ+γ cos2θ. Features of the STHF interactions in N−O−M chains with an M-ion in an orbital degenerate state are examplified by a preliminary analysis of N−O2−−V3+ chains in orthovanadites.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01021675
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  • 5
    Electronic Resource
    Electronic Resource
    Solid-phase replacement of oxygen atoms by fluorine atoms in a fragment of the crystalline structure of the HTSC YBA2Cu3O7−y (1989)
    Springer
    Russian chemical bulletin 38 (1989), S. 1102-1102 
    Details
    ISSN: 1573-9171
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00955468
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  • 6
    Electronic Resource
    Electronic Resource
    The Fe Active Sites in FeZSM-5 Catalyst for Selective Oxidation of CH4 to CH3OH at Room Temperature (2000)
    Springer
    Journal of radioanalytical and nuclear chemistry 246 (2000), S. 149-152 
    Details
    ISSN: 1588-2780
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract It was shown recently that iron complexes formed during the thermal treatment of FeZSM-5 zeolite perform single-turnover cycles of methane oxidation to methanol at ambient conditions when nitrous oxide is used as a source of oxygen. The long-living active intermediate is capable of transferring accepted O atom (called α-oxygen) into C-H bond of methane to produce methanol at 100% selectivity. The present work is aimed to the identification of iron active sites through a comparison of in situ 57Fe Mössbauer spectra of FeZSM-5 after various thermal treatments and reaction stages. It is established that vacuum activation at 900 °C accompanied by a manifold increase of α-centers leads to the transformation of inactive Fe3+ to the active, coordinatively unsaturated Fe2+ states. After α-oxygen loading, active Fe2+ states transform to a new Fe3+ states responsible for further methane oxidation. The latter reaction, as well as reaction with 2H2, is not fully reversible: part of active Fe3+ transforms to other inactive Fe3+ form. On the contrary, reaction of α-oxygen with CO leads to a complete restoration of the initial, vacuum activated Fe2+ states. On the base of joint Mössbauer and catalytic data, the structure and composition of iron active centers are suggested.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006722207492
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  • 7
    Electronic Resource
    Electronic Resource
    Angular dependence of the superexchange interaction Fe3+-O2−-Cr3+ (1975)
    Springer
    Hyperfine interactions 1 (1975), S. 265-281 
    Details
    ISSN: 1572-9540
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The super-exchange interaction parametersI(Fe, Cr) of Fe3+ and Cr3+ in iron doped rate-earth orthochromitesRCr0.99Fe0.01 O3 (R=La, La0.5Nd0.5, Nd, Sm, Gd, Dy, Y, Er, Yb or Lu) have been obtained from57Fe magnetic hyperfine structure measurementsvia the Mössbauer effect. The dependence of the experimental valuesI(Fe, Cr) on the Fe−O−Cr average superexchange angle θ (depending upon the relative size of the rare-earth (RE) ionR 3+) is well described by the equationI(d5, d N ) = α N + β N cosθ + γ N cos2 θ. Within the accessible range of super-exchange angles 142°≲θ≲156°, the Fe3+−O2−−Cr3+ interaction is negative (antiferromagnetic). However, a theoretical analysis predicts a sign reversal forI(Fe, Cr.) at about θ ≈ 162° and thus ferromagnetic character of the interaction between 162° and 180°. The spin-only super-exchange interaction integrals fore g andt 2g electrons, separately, are also calculated. Their angular dependence is accounted for by the behaviour of the antiferromagnetic kinetic and ferromagnetic potential exchange which are of different character when passing from 180° to 90° super-exchange geometry. The magnitude and the sign of the spin-only super-exchange integral for an arbitrary 3d cation, pair is predicted.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01022459
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  • 8
    Electronic Resource
    Electronic Resource
    Supertransferred hyperfine interaction in magnetic insulators (I) (1977)
    Springer
    Hyperfine interactions 3 (1977), S. 429-447 
    Details
    ISSN: 1572-9540
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Two additive contributions to the supertransferred hyperfine (STHF) interaction are suggested to be taken into account in its semi-quantitative analysis of the N-O-M chain: (i) that of bonding molecular orbitals, (ii) that of antibonding orbitals, by calculation of spin-polarization of s-electrons in the N-ion due to the superexchange interaction with d-electrons of the M-ion. Generalized forms of the operator and angular dependence of the STHF interaction were considered due to the use of irreducible tensor operators to the point Oh group. Analytical expressions for the value of the hyperfine fieldH STHF at the nucleus of the N-ion induced by the magnetic M-ion (both in non-degenerateA 1,A 2 ground states and in degenerateE, T 1,T 2 states as well) are derived. The value ofH STHF is dependent upon the type of the M-ion ground state and the geometry of the N-O-M bond. The value ofH STHF induced by M-ions ofA 1,A 2,E states was shown to depend only on the bond angle θ, and that ofT 1,T 2 states on the combinations sin2θ cos 2ϕ, sin2θ sin 2ϕ. The importance of orbital anisotropy in the STHF interaction is emphasized. The orbital anisotropic contribution toH STHF is drastically dependent on the ground state and its splitting in the crystalline field of low symmetry: the isotropic contribution is determined mainly by the occupation numbers of thet 2g ande g subshells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01021575
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  • 9
    Electronic Resource
    Electronic Resource
    57Co emission studies of cupric oxide (1990)
    Springer
    Hyperfine interactions 55 (1990), S. 1187-1193 
    Details
    ISSN: 1572-9540
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Results on the incorporation, valence and spin states of Fe(Co) in CuO (with reference to similar studies on high temperature superconductors) and coupling of the Fe(Co) moment to the Cu magnetism in CuO are presented. Freshly prepared57Co: CuO shows two quadrupole doublets D1 and D2 withQ.S. of 2.49 and 1.52,I.S. of 0.35 and 0.70 mm/s and relative abundance of 74% and 26%, respectively at room temperature, the abundance being dependent on time in a sample exposed to ambient conditions and reaching 38 to 62% fifteen months after preparation. Below,T N=2251K, a typical combined magnetic-quadrupole interaction pattern is observed with a single saturation magnetic hfs of 25.6 T, central shift of 0.82 mm/s and a single |E Q|=1.62 mm/s at 4.2 K. External magnetic field spectra reveal an antiferromagnetic behaviour of the Fe(Co) ion. Temperature dependence of the magnetic hfs is fitted in the framework of the molecular field approximation allowing different spins and coupling constants for Cu and Fe(Co).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02397147
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  • 10
    Electronic Resource
    Electronic Resource
    The nature of the active oxidant in biomimetic oxidation of methane over Fe-ZSM-5 zeolite (1996)
    Springer
    Russian chemical bulletin 45 (1996), S. 1509-1510 
    Details
    ISSN: 1573-9171
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01434252
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