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  • 1995-1999  (7)
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Year
  • 1
    Electronic Resource
    Electronic Resource
    Magnetic, structural, and spin dynamical properties of La1−xCaxMnO3 : The 41st annual conference on magnetism and magnetic materials (1997)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 81 (1997), S. 5488-5490 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Neutron scattering has been used to study the magnetic order, spin dynamics, and structural properties of La1−xCaxMnO3 in the ferromagnetic regime (0〈x〈〈fraction SHAPE="CASE"〉12). For x=〈fraction SHAPE="CASE"〉13(TC=250 K) where the magnetoresistance effects are largest the system behaves as an ideal isotropic ferromagnet at low T, with a gapless (〈0.04 meV) dispersion relation E=Dq2 and DT=0(approximate)155 meV Å2. However, an anomalous diffusive component develops above ∼200 K and dominates the fluctuation spectrum as T→TC. A magnetic field strongly reduces this quasielastic scattering, shifting the spectral weight into the spin wave component of the fluctuation spectrum. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.364576
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  • 2
    Electronic Resource
    Electronic Resource
    The Néel temperature of nanocrystalline chromium (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 1364-1366 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Wide-angle neutron diffraction measurements taken at temperatures from 6 to 250 K indicate that the portion of a chromium sample with a mean grain size of 73 nm is antiferromagnetically ordered at temperatures below 100 K. The Néel temperature (about 120±10 K) for this nanocrystalline sample is suppressed considerably below that of strain-free single-crystal chromium (311 K). © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.360765
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Neutron scattering studies of the magnetic order in RNi2B2C : The 40th annual conference on magnetism and magnetic materials (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 5857-5859 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Neutron diffraction has been used to investigate the magnetic order of RNi2B2C. For R=Er the system orders antiferromagnetically at TN=6.8 K, and this long range order coexists with superconductivity (Tc=11 K). The magnetic structure is an incommensurate, transversely polarized spin-density-wave state, with the modulation wave vector δ along the a axis and the moments along b. δ has a temperature-independent value of 0.5526 (2π/a), with the structure squaring up at low temperatures. For R=Ho the moments also prefer to reside in the a–b plane, but initially an incommensurate c-axis spiral state forms upon cooling, with TN≈TC≈8 K. This c-axis spiral consists of ferromagnetic sheets of holmium moments in the a–b plane, but with each sheet rotated by ∼163° as one proceeds along the c axis. Small a-axis peaks are also observed above the reentrant superconducting transition over a narrow temperature range, but the c-axis peaks dominate. Just below the reentrant transition at ∼5 K the magnetic system locks-in to a simple commensurate antiferromagnetic structure, which permits superconductivity to be restored. The c-axis spiral, the a-axis component, the commensurate antiferromagnetic structure, and the superconducting phase are all in a delicate balance energetically, and this balance may be easily shifted by subtle changes in composition, magnetic field, and pressure. DyNi2B2C orders antiferromagnetically at TN=11 K, with the same commensurate antiferromagnetic structure as found for the holmium material at low temperature. The existence of superconductivity in some samples of DyNi2B2C is consistent with the antiferromagnetic structure observed. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.362150
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  • 4
    Electronic Resource
    Electronic Resource
    Neutron scattering investigation of the structure and spin dynamics in La0.85Sr0.15MnO3 : The 41st annual conference on magnetism and magnetic materials (1997)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 81 (1997), S. 5491-5493 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have performed diffraction and inelastic neutron scattering experiments on a La0.85Sr0.15MnO3 single crystal. In the ferromagnetic phase of this system (Tc=235 K) the long wavelength dispersion relation along the (0,1,0) direction is well represented by E=E0+Dq2, but with the spin wave spectrum almost gapless (E0〈0.1 meV), and with DT=0=83.75±0.36 meV Å2. The spin-wave stiffness constant D(T) exhibits a power law behavior as a function of temperature, and appears to collapse as T→Tc. An orthorhombic–rhombohedral structural phase transition is observed at Ts=360 K, and exhibits a hysteretic character suggesting a first-order transformation. Anomalies in magnetization measurements and Bragg peak intensities indicate the existence of a second phase transition at T=200 K. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.364846
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  • 5
    Electronic Resource
    Electronic Resource
    Cu spin reorientation in Tl(BaSr)PrCu2O7 : The 40th annual conference on magnetism and magnetic materials (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 6568-6570 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The Cu spins in TlBa2PrCu2O7 order at TN≈370 K with a spin structure that is collinear and is characterized by the {1/21/21} wave vector, where the nearest neighbor spins are aligned antiparallel along all three crystallographic directions. If 50% of the Ba atoms are randomly replaced by the smaller Sr atoms to form Tl(BaSr)PrCu2O7, the TN of the Cu spins reduces to 350 K but the magnetic structure that forms below TN is the same. However, at T≈20 K the Cu spins undergo a change in structure, and the spin arrangement is then characterized by the {1/21/21/2} wave vector below T≈12 K. The ground state spin structure of the Cu ions in Tl(BaSr)PrCu2O7 is hence noncollinear, where the spin directions of the nearest neighbor Cu ions in the ab plane remain collinear and antiparallel while along the c axis they are orthogonal. These results demonstrate that the atoms in the BaO layers are also actively participating in the coupling between the Cu ions. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361883
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  • 6
    Electronic Resource
    Electronic Resource
    Spin dynamics of Er3+ in ErBa2Cu3O7−δ : The 41st annual conference on magnetism and magnetic materials (1997)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 81 (1997), S. 4934-4936 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Neutron scattering techniques are used to study the magnetic excitations of the Er ions in superconducting ErBa2Cu3O7, a system where the Er ions order antiferromagnetically at TN=0.62 K and the sublattice magnetization obeys the relation for a 2D S=1/2 Ising model. Our data, which were taken on a cold neutron triple axis spectrometer using a horizontally focusing analyzer, reveal that there is a large gap of about 0.20 meV in the excitation spectrum, about four times the thermal energy kTN, as expected for an Ising system. However, we also observe dispersion of the spin waves in the a-b plane. These excitations are found to renormalize with temperature and only diffuse paramagnetic scattering is observed well above the ordering temperature. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.365002
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  • 7
    Electronic Resource
    Electronic Resource
    Spin dynamics of strongly doped La1−xSrxMnO3 : The 7th joint MMM-intermag conference on magnetism and magnetic materials (1998)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 83 (1998), S. 7342-7344 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Cold neutron triple-axis measurements have been used to investigate the nature of the long-wavelength spin dynamics in strongly doped La1−xSrxMnO3 single crystals with x=0.2 and 0.3. Both systems behave like isotropic ferromagnets at low T, with a gapless (E0〈0.02 meV) quadratic dispersion relation E=E0+Dq2. The values of the spin-wave stiffness constant D are large (DT=0=167 meV Å2 for x=0.2 and DT=0=176 meV Å2 for x=0.3), which directly shows that the electron transfer energy for the d band is large. D exhibits a power law behavior as a function of temperature, and appears to collapse as T→TC. Nevertheless, an anomalously strong quasielastic central component develops and dominates the fluctuation spectrum as T→TC. Bragg scattering indicates that the magnetization near TC exhibits power law behavior, with β(similar, equals)0.30 for both systems, as expected for a three-dimensional ferromagnet. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.367634
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