ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 83 (1985), S. 5988-5997 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Neutron experiments have been performed to measure the induced spin density distribution in single crystals of uranium tetrachloride at low temperature. A structural refinement has also established the atomic positions and thermal parameters at low temperature and these are in agreement with earlier studies. The spin-density distribution, determined with polarized neutrons, shows small but significant deviations from that expected from the single-ion crystal-field model. Fourier difference maps show a small depletion of the (5f) density near the U site and a small positive increase ∼1 A(ring) from the U site and principally along the shorter U–Cl bonds. We ascribe this to population of a 6d (x2−y2) orbital. No significant spin density is associated with the Cl site. Model calculations are presented which qualitatively account for the observed effect and involve electron transfer from the 5f to the 6d antibonding orbital formed as a result of a covalent interaction between the U 6d and Cl p states. This is the first direct observation of covalency in systems involving 5f 6d electrons.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 6816-6818 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The magnetic ordering of an isotope (158Gd) enriched Gd2CuO4 single crystal has been investigated by neutron diffraction in the temperature range 1.5–50 K. The three-dimensional magnetic order of the Cu sublattice is found to disappear abruptly in a narrow temperature range close to 7 K which is just above the ordering temperature of the Gd sublattice [TN(Gd)=6.4 K]. This result is thought to be intimately related to the structural distortion of the CuO planes which gives rise to weak ferromagnetism. The lack of three-dimensional order in the structural distortion imposes itself on the antiferromagnetic arrangement of the Cu sublattice through the Cu-Gd and Gd-Gd interactions and the different and incompatible wave vectors of the Cu and Gd magnetic sublattices.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 3
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Uranium compounds can have an anisotropy that is considerably greater than that found in rare-earth compounds. Early estimates of K1 in ferromagnetic US (Tc = 178 K), for example, were that K1 (approximately-greater-than) 108 erg/cm3. We have re-examined this cubic material and determined K1 in the range of reduced moment (μ/μ0) from 0.1 〈 (μ/μ0) 〈 0.7 and find that it varies logarithmically over almost three orders of magnitude. The highest measured K1 is 2 × 108 erg/cm3 at (μ/μ0) = 0.7, but an extrapolation, which we anticipate on arguments of symmetry, to (μ/μ0)=1, (T=0 K) gives K1 ∼ 1010 erg/cm3, some 20 times more than found in TbFe2 at 0 K. The method we have used is with polarized neutrons. Because the neutron interaction with the magnetic moment is vectorial in nature we can determine individually the magnitude and direction of the moment in an applied field. In many cases this method has advantages over conventional methods, especially when the anisotropy is large.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 4
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 4869-4871 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Magnetization and neutron-diffraction experiments with both polarized and unpolarized neutrons have been performed on single crystals of La1.8Sr0.2NiO4. The susceptibility is highly anisotropic at low temperature, χab (field applied perpendicular to long axis) showing a peak at ∼18 K. However, no evidence has been found for long-range magnetic order. It is speculated that the low-temperature state is a spin glass, with 18 K being the freezing temperature. Polarized neutron diffraction has been used to measure the induced magnetization density in a field of 4.6 T and at 20 K. The results can be understood by using an expanded Ni2+ form factor and invoking a small positive susceptibility at the La site. There is also evidence for covalency between the Ni and O(2) atoms along the c axis. The material distorts from tetragonal (I4/mmm) to orthorhombic (Bmab) at 120±5 K. The structural parameters are similar to those of La2NiO4.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 5
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 57 (1985), S. 3748-3750 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The magnetic form factor of the 5f electrons around the Pu nucleus has been measured with neutrons. The experiment used polarized neutrons and a single crystal of weight 55 mg of PuSb. This compound, which has the NaCl crystal structure, is ferromagnetic below 67 K. The experiment was done in the ordered state with an applied field of 46 kOe. The results show that the Pu ion is trivalent; we see the maximum in f(Q) at Q(approximately-equal-to)2.5 A(ring)−1, which is the unambiguous signature of the 5f5 state. A detailed analysis shows that the ground-state wave function is close to that of a Γ8 state in intermediate coupling. The analysis makes use of the large azimuthal anisotropy (variation in magnetic scattering depending on the angle the scattering vector makes with the magnetic moment) and is not consistent with any possible Γ7 state.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 6
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 63 (1988), S. 3601-3603 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The electronic configuration of trivalent Pu is nominally a 5f5 state in which there is a strong cancellation of the L (orbital) and S (spin) components in the J=5/2 ground state. This leads to small g factors and magnetic moments, and to unusual neutron magnetic form factors f(Q) with maxima at Q values greater than zero. We present here the results of form-factor measurements (taken on the polarized-neutron diffractometer at the ILL) on single crystals of PuSb, PuTe, and PuFe2. These results show that the form factor, which is a measure of the magnetization density of the 5f electrons around the Pu nucleus, is sensitive to the degree of localization of the 5f electrons. For example, in PuSb the 5f electrons are well localized and the form factor is in good agreement with the predictions of intermediate coupling and crystal-field theory. In PuTe f(Q) falls monotonically from a maximum at Q=0, indicating an almost spin-only system. This is produced by wide 5f bands, which give rise to the observed T-independent magnetic susceptibility. In PuFe2, however, a large maximum occurs in f(Q). We believe this arises from strong hybridization of the 5f and 3d Fe electrons, which leads to a reduction in the Pu orbital component.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 7
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 66 (1989), S. 129-136 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Epitaxial layers of ZnSe/ZnS have been grown by metalorganic vapor-phase epitaxy on (001)-oriented GaAs. A microstructural study of the defect content of these layers was performed using the combined techniques of scanning electron microscopy, reflection high-energy electron diffraction, transmission electron microscopy, and microdiffraction. Investigation of the epilayers in the [110] and [11¯0] orientations highlighted the strong anisotropy in the defect content of these ZnSe/ZnS layers. Microtwins were found exclusively in the [11¯0] sample orientation, while examination of the same layers along the orthogonal [110] projection revealed only misfit dislocations. The influence of the differential motion of α and β dislocations in the sphalerite structure is discussed in connection with these observations.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 8
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 63 (1988), S. 3606-3608 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Generalized polarization analysis, in which all three components of polarization of both incident and scattered neutron beams are determined, can be used to probe fine details of magnetic structure. For instance, in certain antiferromagnetic crystals such as Cr2O3 neutrons scattered from reflections containing both nuclear and magnetic components have the direction of their polarization rotated in the plane containing the scattering vector as was demonstrated by Alperin [International Conference on Magnetism (Moscow, 1973)]. The sense of the rotation depends on whether the moments point towards the center of symmetry or away from it. The two corresponding configurations are distinguishable because the coordinating octahedra of oxygen ions are not centrosymmetric and should therefore have different energies. We have used a new technique which exploits the Meissner effect to obtain magnetic isolation to measure the rotation of the neutron polarization by the 102 and 1¯04 (hexagonal) reflections of Cr2O3 between 7 and 320 K. The results show that the lower-energy configuration is the one in which the chromium moments point towards the smaller of the two equilateral triangles of oxygen neighbors. The measured depolarizations were found not to be consistent with a simple domain model.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 9
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 2527-2529 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We demonstrate that scanning transmission electron beam induced conductivity can be used to image the recombination activity of an orthogonal 〈110〉 misfit dislocation array within a relaxed Si/Si1−xGex/Si(001) heterostructure on the submicrometer scale. Correlation with structural images suggests that an array of bunched dissociated 60° misfit dislocations is primarily responsible for the electrical activity in this instance. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 10
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 57 (1990), S. 989-991 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report the measurement of an anisotropy constant ||K1||∼1010 ergs/cm3 in the cubic uranium compound US at 0 K. This is over an order of magnitude greater than that in TbFe2, which has the largest known K1 of a cubic material. A novel method using the scattering of thermal neutrons has been used to determine K1. This measurement, together with our increased understanding of the interactions of 5f electron materials, has some practical implications for magnetic devices.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...