276 research outputs found
Elastic Instabilities within Antiferromagnetically Ordered Phase in the Orbitally-Frustrated Spinel GeCoO
Ultrasound velocity measurements of the orbitally-frustrated GeCoO
reveal unusual elastic instabilities due to the phonon-spin coupling within the
antiferromagnetic phase. Shear moduli exhibit anomalies arising from the
coupling to short-range ferromagnetic excitations. Diplike anomalies in the
magnetic-field dependence of elastic moduli reveal magnetic-field-induced
orbital order-order transitions. These results strongly suggest the presence of
geometrical orbital frustration which causes novel orbital phenomena within the
antiferromagnetic phase.Comment: 5 pages, 3 figure
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
A New Mathematical Approach to Finding Global Solutions of The Magnetic Structure Determination Problem
Determination of magnetic structure is an important analytical procedure utilized in various fields ranging from fundamental condensed-matter physics and chemistry to advanced manufacturing. It is typically performed using a neutron diffraction technique; however, finding global solutions of the magnetic structure optimization problem represents a significant challenge. Generally, it is not possible to mathematically prove that the obtained magnetic structure is a truly global solution and that no solution exists when no acceptable structure is found. In this study, the global optimization technique called semidefinite relaxation of quadratic optimization, which has attracted much interest in the field of applied mathematics, is proposed to use as a new analytical method for the determination of magnetic structure, followed by the application of polarized neutron diffraction data. This mathematical approach allows avoiding spurious local solutions, decreasing the amount of time required to find a tentative solution and finding multiple solutions when they exist
Spin-orbit coupling inactivity of Co ion in geometrically frustrated magnet GeCoO
We report single-crystal neutron diffraction studies on a spinel
antiferromagnet GeCoO, which exhibits magnetic order with a trigonal
propagation vector and tetragonal lattice expansion () below
K. For this inconsistency between spin and lattice in symmetry,
magnetic Bragg reflections with a tetragonal propagation vector were discovered
below . We discuss spin and orbital states of Co ion
underlying the new magnetic component.Comment: 3 pages 2 figures, submitted to ICFCM proceeding (Journal of Physics:
Conference Series, 2011
Carbon formation promoted by hydrogen peroxide in supercritical water
ArticleCARBON. 46(13):1804-1808 (2008)journal articl
Neutron scattering study of role of partial disorder-type spin fluctuations in conductivity of frustrated conductor MnPt
The spin-frustrated conductor MnPt exhibits a characteristic magnetic
structure called partial disorder in which some spin sites can form magnetic
order through the generation of non-ordered sites that locally relieve the
frustration. Here we report the results of a single-crystal inelastic neutron
scattering study of this compound. The measured momentum correlations
of diffusive magnetic scattering reveal that the paramagnetic phase exhibits
short-range spin fluctuations with the same type of partial disorder. Its
relation to conductivity is also discussed.Comment: 5 pages, 4 figure
Molecular spin resonance in the geometrically frustrated MgCr2O4 magnet by inelastic neutron scattering
We measured two magnetic modes with finite and discrete energies in an
antiferromagnetic ordered phase of a geometrically frustrated magnet MgCr2O4 by
single-crystal inelastic neutron scattering, and clarified the spatial spin
correlations of the two levels: one is an antiferromagnetic hexamer and the
other is an antiferromagnetic heptamer. Since these correlation types are
emblematic of quasielastic scattering with geometric frustration, our results
indicate instantaneous suppression of lattice distortion in an ordered phase by
spin-lattice coupling, probably also supported by orbital and charge. The
common features in the two levels, intermolecular independence and discreteness
of energy, suggest that the spin molecules are interpreted as quasiparticles
(elementary excitations with energy quantum) of highly frustrated spins, in
analogy with the Fermi liquid approximation.Comment: 2 figures (13 panels
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