30 research outputs found
Physical properties and crystal chemistry of Ce2Ga12Pt
Single crystals of the new ternary compound Ce2Ga12Pt were prepared by the
self-flux technique. The crystal structure with the space group P4/nbm was
established from single-crystal X-ray diffraction data and presents a
derivative of the LaGa6Ni0.6 prototype. Magnetic susceptibility measurements
show Curie-Weiss behaviour due to local Ce^3+ moments. At high temperatures,
the magnetic anisotropy is dominated by the crystal-electric-field (CEF) effect
with the easy axis along the crystallographic c direction. Ce2Ga12Pt undergoes
two antiferromagnetic phase transitions at T_N,1 = 7.3K and T_N,2 = 5.5K and
presents several metamagnetic transitions for the magnetic field along c.
Specific-heat measurements prove the bulk nature of these magnetic transitions
and reveal a doublet CEF ground state. The 4f contribution to the resistivity
shows a broad maximum at T_max ~ 85K due to Kondo scattering off the CEF ground
state and excited levels.Comment: 12 pages, accepted in J. Phys.: Condens. Matte
Structural investigations of CeIrIn and CeCoIn on macroscopic and atomic length scales
For any thorough investigation of complex physical properties, as encountered
in strongly correlated electron systems, not only single crystals of highest
quality but also a detailed knowledge of the structural properties of the
material are pivotal prerequisites. Here, we combine physical and chemical
investigations on the prototypical heavy fermion superconductors CeIrIn
and CeCoIn on atomic and macroscopic length scale to gain insight into
their precise structural properties. Our approach spans from enhanced
resolution X-ray diffraction experiments to atomic resolution by means of
Scanning Tunneling Microscopy (STM) and reveal a certain type of local features
(coexistence of minority and majority structural patterns) in the tetragonal
HoCoGa-type structure of both compounds.Comment: 8 pages, 5 figures, submitted to JPSJ (SCES 2013
Order and disorder in the modulated phase hp-Mg9Ge5.1
Single crystals of Mg9Ge5.1(2) were obtained at a pressure of 5 GPa in the temperature range 723 to 1273 K. The metastable high-pressure phase exhibits a crystal structure, which may be described as a host-guest variety of an UCl3-type framework. The atomic arrangement is characterized by a host crystal structure Mg9Ge3 with disordered germanium guests (≈2 Ge per formula unit) in the channels. The composite arrangement undergoes incommensurate modulation. Upon heating at ambient pressure, the phase transforms into the thermodynamically stable compounds Mg2Ge and Ge at 496(5) K. Measurements of the magnetic susceptibility indicate diamagnetic behavior between 75 and 350 K
Spatial separation of covalent, ionic, and metallic interactions in <tex>Mg_{11}Rh_{18}B_{8}</tex>
Crystal Chemistry and Physics of UCd11
In the phase diagram U-Cd, only one compound has been identified so far─UCd11 (space group Pm3̅m). Since the discovery of this material, the physical properties of UCd11 have attracted a considerable amount of attention. In particular, its complex magnetic phase diagram─as a result of tuning with magnetic field or pressure─is not well-understood. From a chemical perspective, a range of lattice parameter values have been reported, suggesting a possibility of a considerable homogeneity range, i.e., UCd11-x. In this work, we perform a simultaneous study of crystallographic features coupled with measurements of physical properties. This work sheds light on the delicate relationship between the intrinsic crystal chemistry and magnetic properties of UCd11
<tex>Sn_{20.5-3.5}As_{22}I_{8}:$</tex> a largely disordered cationic clathrate with a new type of superstructure and abnormally low thermal conductivity
Crystal Chemistry and Physics of UCd<sub>11</sub>
In the phase diagram U-Cd, only one compound has been
identified
so farUCd11 (space group Pm3Ì…m). Since the discovery of this material, the physical properties
of UCd11 have attracted a considerable amount of attention.
In particular, its complex magnetic phase diagramas a result
of tuning with magnetic field or pressureis not well-understood.
From a chemical perspective, a range of lattice parameter values have
been reported, suggesting a possibility of a considerable homogeneity
range, i.e., UCd11–x. In this work,
we perform a simultaneous study of crystallographic features coupled
with measurements of physical properties. This work sheds light on
the delicate relationship between the intrinsic crystal chemistry
and magnetic properties of UCd11
BaGe<sub>6</sub> and BaGe<sub>6‑x</sub>: Incommensurately Ordered Vacancies as Electron Traps
We
report the high-pressure high-temperature synthesis of the germanium-based
framework compounds BaGe<sub>6</sub> (<i>P</i> = 15 GPa, <i>T</i> = 1073 K) and BaGe<sub>6–<i>x</i></sub> (<i>P</i> = 10 GPa, <i>T</i> = 1073 K) which
are metastable at ambient conditions. In BaGe<sub>6‑<i>x</i></sub>, partial fragmentation of the BaGe<sub>6</sub> network involves
incommensurate modulations of both atomic positions and site occupancy.
Bonding analysis in direct space reveals that the defect formation
in BaGe<sub>6–<i>x</i></sub> is associated with the
establishment of free electron pairs around the defects. In accordance
with the electron precise composition of BaGe<sub>6‑<i>x</i></sub> for <i>x</i> = 0.5, physical measurements evidence
semiconducting electron transport properties which are combined with
low thermal conductivity
BaGe<sub>6</sub> and BaGe<sub>6‑x</sub>: Incommensurately Ordered Vacancies as Electron Traps
We
report the high-pressure high-temperature synthesis of the germanium-based
framework compounds BaGe<sub>6</sub> (<i>P</i> = 15 GPa, <i>T</i> = 1073 K) and BaGe<sub>6–<i>x</i></sub> (<i>P</i> = 10 GPa, <i>T</i> = 1073 K) which
are metastable at ambient conditions. In BaGe<sub>6‑<i>x</i></sub>, partial fragmentation of the BaGe<sub>6</sub> network involves
incommensurate modulations of both atomic positions and site occupancy.
Bonding analysis in direct space reveals that the defect formation
in BaGe<sub>6–<i>x</i></sub> is associated with the
establishment of free electron pairs around the defects. In accordance
with the electron precise composition of BaGe<sub>6‑<i>x</i></sub> for <i>x</i> = 0.5, physical measurements evidence
semiconducting electron transport properties which are combined with
low thermal conductivity