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  • 75.30.Et  (1)
  • PACS. 75.25+z Spin arrangements in magnetically ordered materials (including neutron and spin-polarized electron studies, synchrotron-source x-ray scattering, etc.) - 61.66.-f Structure of specific crystalline solids - 65.40.+g Heat capacities of solids  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Collapse of the magnetic ordering and structural anomalies in the U La S system: neutron diffraction and specific heat measurements (1999)
    Springer
    The European physical journal 9 (1999), S. 605-611 
    Details
    ISSN: 1434-6036
    Keywords: PACS. 75.25+z Spin arrangements in magnetically ordered materials (including neutron and spin-polarized electron studies, synchrotron-source x-ray scattering, etc.) - 61.66.-f Structure of specific crystalline solids - 65.40.+g Heat capacities of solids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: We report specific heat and neutron diffraction measurements of seven samples in the solid solution system UxLa1-xS. All samples have the simple fcc NaCl crystal structure. Both specific heat and neutron diffraction confirm the suggestion from the earlier magnetic measurements that the ferromagnetism disappears abruptly at 0.57. Near there is a doubling of the electronic contribution to the specific heat, as compared to the value of 23 mJ mol-1K-2 in pure US. Around the widths of the nuclear Bragg peaks show a considerable broadening, as well as anomalies in the mean lattice parameter, as compared to those expected from Vegard's law. A preliminary analysis suggests this broadening may be due to a loss of long range lattice order near . However, these changes are independent of temperature, so that further experiments are necessary before they can be associated with the changes in magnetic behavior at .
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s100510050804
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  • 2
    Electronic Resource
    Electronic Resource
    Spin waves and exchange interactions in the antiferromagnetic garnets with Fe3+ in the octahedral sites (1993)
    Springer
    The European physical journal 92 (1993), S. 443-449 
    Details
    ISSN: 1434-6036
    Keywords: 75.25.+z ; 75.30.Et
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The results of an inelastic neutron scattering study of the spin wave spectrum for the garnet Fe2Ca3Si3O12(FeSiG) are presented. We compare the exchange parameters for this garnet and for the Ge-species (Fe2Ca3Ge3O12(feGeG)) having the same magnetic structure. We relate the differences found with structural information from powder neutron diffraction. In this way the super exchange paths viap σ orbitals of intermediate oxygen atoms can be identified. We discuss the effect of a small number (3.2(5)%) of Mn2+ impurities in the 24c sites. These lead to an effective ferromagnetic exchange between the Fe3+ ions and drastically renormalize the average exchange constants. An estimate for the Fe3+−Mn2+ indirect exchange between a and c sites of 6(1) K is obtained. The exchange parameters for the pure FeSiG are found to beJ 1=1.16(4) K,J 1=0.96(4K andJ 2=−1.24(4) K for nearest and next nearest neighbours, respectively. These values apply for a moment of 4.02(4) μB per iron atom as obtained from a structure refinement of powder diffraction data. Finally we present results for FeSiG of a high resolution study of the excitations at the zone centre in an attempt to verify our earlier findings of a quantum spin wave gap for FeGeG. In contrast to the earlier measurements, we could follow the acoustical branch to much lower energies using a timeof-flight spectrometer. We found indications for a crossing of the two low lying spin wave branches, the acoustical one extrapolating to the anisotropy gap of 0.005 THz and the “antiphase” branch extrapolating to the quantum gap of 0.02 THz.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01320506
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