149 research outputs found
Detailed Measurements of Characteristic Profiles of Magnetic Diffuse Scattering in ErBC
Detailed neutron diffraction measurements on a single crystalline
ErBC were performed. We observed magnetic diffuse scattering which
consists of three components just above the transition temperatures, which is
also observed in characteristic antiferroquadrupolar ordering compounds
HoBC and TbBC. The result of this experiments indicates that
the antiferroquadrupolar interaction is not dominantly important as a origin of
the magnetic diffuse scattering.Comment: 5 pages, 5 figures, submitted to J. Phys. Soc. Jp
Multipole tensor analysis of the resonant x-ray scattering by quadrupolar and magnetic order in DyB2C2
Resonant x-ray scattering (RXS) experiment has been performed for the (3 0
1.5) superlattice reflection in the antiferroquadrupolar and antiferromagnetic
phase of DyB2C2. Azimuthal-angle dependence of the resonance enhanced
intensities for both dipolar (E1) and quadrupolar (E2) resonant processes has
been measured precisely with polarization analysis. Every scattering channel
exhibits distinctive azimuthal dependence, differently from the symmetric
reflection at (0 0 0.5) which was studied previously. We have analyzed the
results using a theory developed by Lovesey et al., which directly connects
atomic tensors with the cross-section of RXS. The fitting results indicate that
the azimuthal dependences can be explained well by the atomic tensors up to
rank 2. Rank 3 and rank 4 tensors are reflected in the data very little. In
addition, The coupling scheme among the 4f quadrupolar moment, 5d ortitals, and
the lattice has been determined from the interference among the Thomson
scattering from the lattice distortion and the resonant scatterings of E1 and
E2 processes. It has also been established from the RXS of the (3 0 1.5)
reflection that the canting of the 4f quadrupolar moments exists up to T_Q. We
also discuss a possible wavefunction of the ground state from the point-charge
model calculation.Comment: 9 pages, 10 figure
Thermal Properties of Heavy Fermion Compound YbP
Low-temperature specific heat and its field-dependence up to 16 T was
measured in a stoichiometric single crystal of YbP. A sharp peak was observed
at {\it T} = 0.53 K in zero magnetic field. Application of external
field seems to induce a new magnetic phase above 11 T. The field dependence of
the transition temperature in the high-field phase is different from that of
the low field phase. The linear coefficient of the electronic specific heat is
estimated as 120 mJ/mole K from low temperature specfic heat, suggesting
heavy Fermion state in YbP.Comment: to be published in J.Phys.Soc.Jpn on May, 200
Modified Cross-Correlation for Efficient White-Beam Inelastic Neutron Scattering Spectroscopy
We describe a method of white-beam inelastic neutron scattering for improved
measurement efficiency. The method consists of matrix inversion and selective
extraction. The former is to resolve each incident energy component from the
white-beam data, and the latter eliminates contamination by elastic components,
which produce strong backgrounds that otherwise obfuscate the inelastic
scattering components. In this method, the optimal experimental condition to
obtain high efficiency will strongly depend on the specific aim of the
individual experiments.Comment: 6 pages, 3 figure
Magnetic Phase Diagrams with Possible Field-induced Antiferroquadrupolar Order in TbBC
Magnetic phase diagrams of a tetragonal antiferromagnet TbBC were
clarified by temperature and field dependence of magnetization. It is
noticeable that the N{\'e}el temperature in TbBC is anomalously
enhanced with magnetic fields, in particular the enhancement reaches 13.5 K for
the direction at 10 T. The magnetization processes as well as the
phase diagrams are well interpreted assuming that there appear field-induced
antiferroquadrupolar ordered phases in TbBC. The phase diagrams of the
AFQ compounds in RBC are systematically understood in terms of the
competition with AFQ and AFM interactions.Comment: 4 pages, 4 figures, RevTeX
Relation between crystal and magnetic structures of the layered manganites La2-2xSr1+2xMn2O7 (0.30 =< x =< 0.50)
Comprehensive neutron-powder diffraction and Rietveld analyses were carried
out to clarify the relation between the crystal and magnetic structures of
La2-2xSr1+2xMn2O7 (0.30 =< x =< 0.50). The Jahn-Teller (JT) distortion of Mn-O6
octahedra, i.e., the ratio of the averaged apical Mn-O bond length to the
equatorial Mn-O bond length, is Delta_JT=1.042(5) at x=0.30, where the magnetic
easy-axis at low temperature is parallel to the c axis. As the JT distortion
becomes suppressed with increasing x, a planar ferromagnetic structure appears
at x =< 0.32, which is followed by a canted antiferromagnetic (AFM) structure
at x =< 0.39. The canting angle between neighboring planes continuously
increases from 0 deg (planar ferromagnet: 0.32 =< x < 0.39) to 180 deg (A-type
AFM: x=0.48 where Delta_JT=1.013(5)). Dominance of the A-type AF structure with
decrease of JT distortion can be ascribed to the change in the eg orbital state
from d3z^2-r^2 to dx^2-y^2
Neutron Scattering Study of the Localized Mode in the beta-Pyrochlore Superconductors AOs2O6
Inelastic neutron scattering and neutron powder diffraction experiments were
carried out to investigate a localized mode, proposed from various bulk
measurements, in the beta-pyrochlore AOs2O6 (A=K, Rb, Cs). The localized mode
was identified in all the three compounds as well as another beta-pyrochlore
CsW2O6. The anharmonicity of the mode is weak in RbOs2O6 and CsOs2O6 but
substantial in KOs2O6.Comment: 12 pages, 6 figures; typos and graph correcte
Emergence of magnetic long-range order in frustrated pyrochlore NdIrO with metal-insulator transition
In this study, we performed powder neutron diffraction and inelastic
scattering measurements of frustrated pyrochlore NdIrO, which
exhibits a metal-insulator transition at a temperature of 33 K.
The diffraction measurements revealed that the pyrochlore has an
antiferromagnetic long-range structure with propagation vector of
(0,0,0) and that it grows with decreasing temperature below 15 K. This
structure was analyzed to be of the all-in all-out type, consisting of highly
anisotropic Nd magnetic moments of magnitude ,
where is the Bohr magneton. The inelastic scattering measurements
revealed that the Kramers ground doublet of Nd splits below . This suggests the appearance of a static internal magnetic field at the
Nd sites, which probably originates from a magnetic order consisting of
Ir magnetic moments. Here, we discuss a magnetic structure model for the
Ir order and the relation of the order to the metal-insulator transition in
terms of frustration.Comment: 6 pages, 1 table, 3 figure
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