CePt3Si is a novel heavy fermion superconductor, crystallizing in the CePt3B structure as a tetragonally distorted low symmetry variant of the AuCu3 structure type. CePt3Si exhibits antiferromagnetic order at T(N) approximately 2.2 K and enters into a heavy fermion superconducting state at T(c) approximately 0.75 K. Large values of H(')(c2) approximately -8.5 T/K and H(c2)(0) approximately 5 T refer to heavy quasiparticles forming Cooper pairs. Hitherto, CePt3Si is the first heavy fermion superconductor without a center of symmetry.
CeNiGe 3 , crystallizing in the orthorhombic SmNiGe 3 -type crystal structure, was studied by means of dc and ac magnetic susceptibility, magnetization, electrical resistivity, magnetoresistivity, Hall effect, and specific-heat measurements. The compound orders antiferromagnetically at T N ϭ5.5 K due to the presence of well localized 4 f magnetic moments, which are partly screened via a Kondo-like mechanism. The electrical behavior is governed by an interplay of Ruderman-Kittel-Kasuya-Yosida and Kondo interactions modified by crystal-field effects. The Kondo temperature is of similar magnitude as T N , and the overall crystal electric field splitting is of the order of 160 K. The low-temperature specific heat exhibits some enhancement indicating the formation of moderate-heavy quasiparticles in the antiferromagnetic state. The specific variation with applied magnetic field of the main physical characteristics of CeNiGe 3 points at a complex magnetic structure of the compound in the ordered region.
[micro-Tris(1,4-bis(tetrazol-1-yl)butane-N4,N4')iron(II)] bis(hexafluorophosphate), [Fe(btzb)(3)](PF(6))(2), crystallizes in a three-dimensional 3-fold interlocked structure featuring a sharp two-step spin-crossover behavior. The spin conversion takes place between 164 and 182 K showing a discontinuity at about T(1/2) = 174 K and a hysteresis of about 4 K between T(1/2) and the low-spin state. The spin transition has been independently followed by magnetic susceptibility measurements, (57)Fe-Mössbauer spectroscopy, and variable temperature far and midrange FTIR spectroscopy. The title compound crystallizes in the trigonal space group P3 (No. 147) with a unit cell content of one formula unit plus a small amount of disordered solvent. The lattice parameters were determined by X-ray diffraction at several temperatures between 100 and 300 K. Complete crystal structures were resolved for 9 of these temperatures between 100 (only low spin, LS) and 300 K (only high spin, HS), Z = 1 [Fe(btzb)(3)](PF(6))(2): 300 K (HS), a = 11.258(6) A, c = 8.948(6) A, V = 982.2(10) A(3); 100 K (LS), a = 10.989(3) A, c = 8.702(2) A, V = 910.1(4) A(3). The molecular structure consists of octahedral coordinated iron(II) centers bridged by six N4,N4' coordinating bis(tetrazole) ligands to form three 3-dimensional networks. Each of these three networks is symmetry related and interpenetrates each other within a unit cell to form the interlocked structure. The Fe-N bond lengths change between 1.993(1) A at 100 K in the LS state and 2.193(2) A at 300 K in the HS state. The nearest Fe separation is along the c-axis and identical with the lattice parameter c.
Combining experiments and ab initio models we report on SrPt4Ge12 and BaPt4Ge12 as members of a novel class of superconducting skutterudites, where Sr or Ba atoms stabilize a framework entirely formed by Ge atoms. Below T(c)=5.35 and 5.10 K for BaPt4Ge12 and SrPt4Ge12, respectively, electron-phonon coupled superconductivity emerges, ascribed to intrinsic features of the Pt-Ge framework, where Ge-p states dominate the electronic structure at the Fermi energy.
We report on investigations of type I clathrate Si and Ge compounds with Ba
partially substituted by rare earth atoms. Novel compounds from framework-deficient
solid solutions Ba8 Alx Si42−3/4x □4−1/4x
and Ba8 Gax Si42−3/4x □4−1/4x (x = 8, 12, 16;
□, open
square...
lattice defect) have been prepared and characterized. All x-ray intensity data are consistent
with the standardized clathrate I-Ba8Al16Ge30 type structure (space group Pm3̄n).
In rare earth substituted clathrates, Eu2Ba6MxSi46−x (M = Cu,
Al, Ga), rare earth atoms completely occupy the
2a
position and thus form a new quaternary ordered version of the Ba8Al16Ge30
structure type. From a geometrical analysis of clathrate crystal structures, a
systematic scheme for all known clathrate compounds is proposed. All clathrates
studied are metals with low electrical conductivity. The highest Seebeck coefficient
in the present series is deduced for Ba8In16Ge30, S = −75μV K−1,
indicating transport processes dominated by electrons as carriers. The Eu-based
clathrates investigated exhibit long-range magnetic order as high as 32 K for
Eu2Ba6Al8Si36 of presumably ferromagnetic type. Magnetic susceptibility
indicates in all cases a 2+ ground state for the Eu ions, in fine agreement with LIII
absorption edge spectra.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.