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  • 1995-1999  (7)
  • 1985-1989  (10)
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  • 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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  • 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
    Magnetic order in RBa2Cu2O6+x (invited) (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 64 (1988), S. 6065-6070 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Neutron scattering results on the RBa2 Cu3 O6+x (R=rare earth) class of systems are reviewed. For the oxygen-deficient systems (x〈0.5), which are semiconducting, the Cu ions are observed to order with Néel temperatures as high as 500 K. The magnetic structure consists of strong nearest-neighbor antiferromagnetic couplings of the Cu spins within the Cu-O2 layers, while nearest-neighbor spins in adjacent layers are also aligned antiferromagnetically. The moments are constrained in the tetragonal plane. At lower temperatures the Cu moments in the oxygen-deficient "chain'' layers also order antiferromagnetically, with a moment that can be quite substantial (∼ 1/2 μB). Both transition temperatures are very sensitive to the oxygen concentration. The magnetic heavy rare-earth compounds, on the other hand, order antiferromagnetically at very low temperatures, analogous to the "conventional'' magnetic-superconductor systems such as RMo6 S8 and RRh4 B4. The ordering is not very sensitive to the oxygen concentration, and the antiferromagnetic state coexists with superconductivity. Differences in the ordering behavior are ascribed to crystal-field effects, which are briefly discussed. Finally, small-angle neutron scattering results in the vicinity of the superconducting transition temperature are also discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.342124
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  • 7
    Electronic Resource
    Electronic Resource
    Spin-wave excitations in amorphous Fe78B13Si9 (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 63 (1988), S. 4083-4085 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Inelastic neutron scattering measurements have been used to study the long wavelength spin dynamics of the high Tc amorphous ferromagnetic alloy Fe78B13Si9 (Metglas 2605S2). Spin waves were observed over the accessible wave-vector range of 0.06 A(ring)−1≤q≤0.12 A(ring)−1, for temperatures between 473 K (0.67 Tc) and 705 K (0.99 Tc). The magnon dispersion curves exhibit the conventional quadratic relationship E=D(T)q2+Δ, typical of an isotropic ferromagnet, where the small energy gap Δ≈0.05 meV is attributed primarily to the dipole-dipole interaction. An estimate of the T=0 value of D≈156 meV A(ring)2 was obtained from a plot of D(T) vs T extrapolated to low temperatures, while the Curie temperature of 710 K was obtained from the extrapolation of D(T) to zero at high temperatures. Spin-wave linewidth data for T/Tc≈0.95 showed the q4 wave-vector dependence expected for magnon-magnon interactions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.340556
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  • 8
    Electronic Resource
    Electronic Resource
    Antiferromagnetic structure of the cubic superconductor ErPd2Sn (1987)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 61 (1987), S. 3371-3373 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Elastic and inelastic neutron scattering measurements have been made on the cubic Heusler alloy ErPd2Sn, which becomes superconducting at Ts =1.17 K. Antiferromagnetic correlations are found to develop for T〉Ts, with an antiferromagnetic transition occurring at T≈1.0 K. The magnetic structure is found to be type II, in which the fcc Er unit cell doubles along all three crystallographic directions. However, there are additional satellites of the allowed reflections which indicate a modulated component of the magnetization density. In addition, the linewidths are broader than instrumental resolution and distinctly non-Gaussian in shape. Inelastic measurements show a broad distribution of scattering extending to energy transfers greater than 1 meV, as well as two distinct crystal field levels at 7.4 and 11.1 meV.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.338775
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  • 9
    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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  • 10
    Electronic Resource
    Electronic Resource
    Spin stiffness anomaly in the reentrant spin-glass (Fe0.25Ni0.75)0.75P0.16B0.06Al0.03 (1985)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 57 (1985), S. 3473-3475 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Low field magnetization measurements have shown that the amorphous alloy (Fe0.25Ni0.75)0.75P0.16B0.06Al0.03 becomes a demagnetization-limited ferromagnet below a Curie temperature Tc of 200 K, but that the spontaneous magnetization vanishes again below a reentrant temperature TR of 4 K. Inelastic neutron scattering measurements have been performed to study the spin-wave dynamics as the spin-glass state is entered from the ferromagnetic state. The observed spin-wave peak positions decrease in energy and the linewidths increase as the temperature is lowered towards TR. A detailed analysis based on both the double Lorentzian and damped harmonic oscillator forms of the spectral weight function shows that the spin-wave energies strongly decrease as the temperature is lowered and the excitations become heavily damped over the range of wave vectors (0.04 A(ring)−1〈q〈0.18 A(ring)−1) studied. An elastic component of the magnetic scattering, attributed to a spin-glass order parameter, is also observed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.335030
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