113 research outputs found
Single-crystal growth of the ternary BaFeAs phase using the vertical Bridgman technique
Ternary Ba-Fe-As system has been studied to determine a primary
solidification field of the BaFeAs phase. We found that the
BaFeAs phase most likely melts congruently and primarily solidifies
either in the FeAs excess or BaAs excess liquid. Knowing the
primary solidification field, we have performed the vertical Bridgman growth
using the starting liquid composition of BaFeAs. Large
single crystals of the typical size 10x4x2 mm were obtained and their
quality was confirmed by X-ray Laue and neutron diffraction.Comment: Submitted to Jpn. J. Appl. Phys.; revise
Whirling spin order in the quasicrystal approximant AuAlTb
Neutron powder diffraction experiment has been performed on the quasicrystal
approximant AuAlTb, a body-center-cubic crystal of
icosahedral spin clusters. The long-range antiferromagnetic order was confirmed
at the transition temperature K. The magnetic structure
consists of noncoplanar whirling spins on the icosahedral clusters, arranging
antiferroic-manner. A simple icosahedral spin-cluster model with uniaxial
anisotropy accounts well the whirling spin order as well as the in-field
metamagnetic transition, indicating that the icosahedral symmetry is essential.Comment: 6 pages, 4 figure
Quantum Phase Transition in the Itinerant Antiferromagnet (V0.9Ti0.1)2O3
Quantum-critical behavior of the itinerant electron antiferromagnet
(V0.9Ti0.1)2O3 has been studied by single-crystal neutron scattering. By
directly observing antiferromagnetic spin fluctuations in the paramagnetic
phase, we have shown that the characteristic energy depends on temperature as
c_1 + c_2 T^{3/2}, where c_1 and c_2 are constants. This T^{3/2} dependence
demonstrates that the present strongly correlated d-electron antiferromagnet
clearly shows the criticality of the spin-density-wave quantum phase transition
in three space dimensions.Comment: 4 pages, 4 figure
Degenerate ground state in the classical pyrochlore antiferromagnet NaMn(CO)Cl
In an ideal classical pyrochlore antiferromagnet without perturbations, an
infinite degeneracy at a ground state leads to absence of a magnetic order and
spin-glass transition. Here we present NaMn(CO)Cl as a new
candidate compound where classical spins are coupled antiferromagnetically on
the pyrochlore lattice, and report its structural and magnetic properties.The
temperature dependences of the magnetic susceptibility and heat capacity, and
the magnetization curve are consistent with those of an = 5/2 pyrochlore
lattice antiferromagnet with nearest-neighbor interactions of 2 K. Neither an
apparent signature of a spin-glass transition nor a magnetic order is detected
in magnetization and heat capacity measurements, or powder neutron diffraction
experiments. On the other hand, an antiferromagnetic short-range order from the
nearest neighbors is evidenced by the -dependence of the diffuse scattering
which develops around 0.85 \AA. A high degeneracy near the ground state
in NaMn(CO)Cl is supported by the magnetic entropy estimated as
almost 4 J K mol at 0.5 K.Comment: 9 pages, 7 figures, accepted to PR
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