5 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
Polycation–Polyanion Architecture of the Intermetallic Compound Mg3−xGa1+xIr
Mg3−xGa1+xIr (x = 0.05) was synthesized by direct reaction of the elements in welded tantalum containers at 1200 °C and subsequent annealing at 500 °C for 30 days. Its crystal structure represents a new prototype and was determined by single-crystal technique as follows: space group P63/mcm, Pearson symbol hP90, Z = 18, a = 14.4970(3) Å, c = 8.8638(3) Å. The composition and atomic arrangement in Mg3GaIr do not follow the 8–N rule due to the lack of valence electrons. Based on chemical bonding analysis in positional space, it was shown that the title compound has a polycationic–polyanionic organization. In comparison with other known intermetallic substances with this kind of bonding pattern, both the polyanion and the polyanion are remarkably complex. Mg3−xGa1+xIr is an example of how the general organization of intermetallic substances (e.g., formation of polyanions and polycations) can be understood by extending the principles of 8–N compounds to electron-deficient materials with multi-atomic bonding
Intermediate-Valence Ytterbium Compound Yb<sub>4</sub>Ga<sub>24</sub>Pt<sub>9</sub>: Synthesis, Crystal Structure, and Physical Properties
The
title compound was synthesized by a reaction of the elemental educts
in a corundum crucible at 1200 °C under an Ar atmosphere. The
excess of Ga used in the initial mixture served as a flux for the
subsequent crystal growth at 600 °C. The crystal structure of
Yb<sub>4</sub>Ga<sub>24</sub>Pt<sub>9</sub> was determined from single-crystal
X-ray diffraction data: new prototype of crystal structure, space
group <i>C</i>2<i>/m</i>, Pearson symbol <i>mS</i>74, <i>a</i> = 7.4809(1) Å, <i>b</i> = 12.9546(2) Å, <i>c</i> = 13.2479(2) Å, β
= 100.879(1)°, <i>V</i> = 1260.82(6) Å<sup>3</sup>, <i>R</i><sub><i>F</i></sub> = 0.039 for 1781
observed reflections and 107 variable parameters. The structure is
described as an <i>ABABB</i> stacking of two slabs with
trigonal symmetry and compositions Yb<sub>4</sub>Ga<sub>6</sub> (<i>A</i>) and Ga<sub>12</sub>Pt<sub>6</sub> (<i>B</i>). The hard X-ray photoelectron spectrum (HAXPES) of Yb<sub>4</sub>Ga<sub>24</sub>Pt<sub>9</sub> shows both Yb<sup>2+</sup> and Yb<sup>3+</sup> contributions as evidence of an intermediate valence state
of ytterbium. The evaluated Yb valence of ∼2.5 is in good agreement
with the results obtained from the magnetic susceptibility measurements.
The compound is a bad metallic conductor