85 research outputs found
Negative thermal expansion in the Prussian Blue analog Zn3[Fe(CN)6]2: X-ray diffraction and neutron vibrational studies
The cubic Prussian Blue (PB) analog, Zn3 [Fe(CN)6]2, has been studied by
X-ray powder diffraction and inelastic neutron scattering (INS). X-ray data
collected at 300 and 84 K revealed negative thermal expansion (NTE) behaviour
for this material. The NTE coefficient was found to be -31.1 x 10-6 K-1. The
neutron vibrational spectrum for Zn3[Fe(CN)6]2.xH2O, was studied in detail. The
INS spectrum showed well-defined, well-separated bands corresponding to the
stretching of and deformation modes of the Fe and Zn octahedra, all below 800
cm-1.Comment: 4 pages, 3 figure
Unusual signatures of the ferromagnetic transition in the heavy Fermion compound UMnAl
Magnetic susceptibility results for single crystals of the new cubic
compounds UTAl (T=Mn, V, and Mo) are reported. Magnetization,
specific heat, resistivity, and neutron diffraction results for a single
crystal and neutron diffraction and inelastic spectra for a powder sample are
reported for UMnAl. For T = V and Mo, temperature independent Pauli
paramagnetism is observed. For UMnAl, a ferromagnetic transition is
observed in the magnetic susceptibility at = 20 K. The specific heat
anomaly at is very weak while no anomaly in the resistivity is seen at
. We discuss two possible origins for this behavior of UMnAl:
moderately small moment itinerant ferromagnetism, or induced local moment
ferromagnetism.Comment: 5 pages, 5 figures, to be published in Phys. rev.
Lattice anisotropy in uranium ternary compounds: UTX
Several U-based intermetallic compounds (UCoGe, UNiGe with the TiNiSi structure type and UNiAl with the ZrNiAl structure type) and their hydrides were studied from the point of view of compressibility and thermal expansion. Confronted with existing data for the compounds with the ZrNiAl structure type a common pattern emerges. The direction of the U-U bonds with participation of the 5f states is distinctly the "soft" crystallographic direction, exhibiting also the highest coefficient of linear thermal expansion. The finding leads to an apparent paradox: the closer the U atoms are together in a particular direction the better they can be additionally compressed together by applied hydrostatic pressure. (C) 2012 Elsevier B. V. All rights reserved
Structural, electronic, magnetic, and thermal properties of single-crystalline UNi0.5Sb2
We studied the properties of the antiferromagnetic (AFM) UNi0.5Sb2 (TN
\approx 161 K) compound in Sb-flux grown single crystals by means of
measurements of neutron diffraction, magnetic susceptibility ({\chi}), specific
heat (Cp), thermopower (S), thermal conductivity ({\kappa}), linear thermal
expansion ({\Delta}L/L), and electrical resistivity ({\rho}) under hydrostatic
pressures (P) up to 22 kbar. The neutron diffraction measurements revealed that
the compound crystallizes in the tetragonal P42/nmc structure, and the value of
the U-moments yielded by the histograms at 25 K is \approx 1.85 \pm 0.12
{\mu}B/U-ion. In addition to the features in the bulk properties observed at
TN, two other hysteretic features centered near 40 and 85 K were observed in
the measurements of {\chi}, S, {\rho}, and {\Delta}L/L. Hydrostatic pressure
was found to raise TN at the rate of \approx 0.76 K/kbar, while suppressing the
two low temperature features. These features are discussed in the context of
Fermi surface and hybridization effects.Comment: 17 pages, 8 figure
Magnetic structure of antiferromagnetic NdRhIn5
The magnetic structure of antiferromagnetic NdRhIn5 has been determined using
neutron diffraction. It has a commensurate antiferromagnetic structure with a
magnetic wave vector (1/2,0,1/2) below T_N = 11K. The staggered Nd moment at
1.6K is 2.6mu_B aligned along the c-axis. We find the magnetic structure to be
closely related to that of its cubic parent compound NdIn3 below 4.6K. The
enhanced T_N and the absence of additional transitions below T_N for NdRhIn5
are interpreted in terms of an improved matching of the
crystalline-electric-field (CEF), magnetocrystalline, and exchange interaction
anisotropies. In comparison, the role of these competing anisotropies on the
magnetic properties of the structurally related compound CeRhIn5 is discussed.Comment: 4 pages, 4 figure
Magnetocrystalline Anisotropy in a Single Crystal of CeNiGe2
We report measurements on single crystals of orthorhombic CeNiGe2, which is
found to exhibit highly anisotropic magnetic and transport properties. The
magnetization ratio M(H//b)/M(H^b) at 2 K is observed to be about 18 at 4 T and
the electrical resistivity ratio r//b/r^b is about 70 at room temperature. It
is confirmed that CeNiGe2 undergoes two-step antiferromagnetic transition at 4
and 3 K, as reported for polycrystalline samples. The application of magnetic
field along the b axis (the easy magnetization axis) stabilizes a ferromagnetic
correlation between the Ce ions and enhances the hopping of carriers. This
results in large negative magnetoresistance along the b axis.Comment: 24 pages, including 9 figure
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