Magnetic and transport properties of i-RR-Cd icosahedral quasicrystals (RR = Y, Gd-Tm)

We present a detailed characterization of the recently discovered i-$R$-Cd ($R$ = Y, Gd-Tm) binary quasicrystals by means of x-ray diffraction, temperature-dependent dc and ac magnetization, temperature-dependent resistance and temperature-dependent specific heat measurements. Structurally, the broadening of x-ray diffraction peaks found for i-$R$-Cd is dominated by frozen-in phason strain, which is essentially independent of $R$. i-Y-Cd is weakly diamagnetic and manifests a temperature-independent susceptibility. i-Gd-Cd can be characterized as a spin-glass below 4.6 K via dc magnetization cusp, a third order non-linear magnetic susceptibility peak, a frequency-dependent freezing temperature and a broad maximum in the specific heat. i-$R$-Cd ($R$ = Ho-Tm) is similar to i-Gd-Cd in terms of features observed in thermodynamic measurements. i-Tb-Cd and i-Dy-Cd do not show a clear cusp in their zero-field-cooled dc magnetization data, but instead show a more rounded, broad local maximum. The resistivity for i-$R$-Cd is of order 300 $\mu \Omega$ cm and weakly temperature-dependent. The characteristic freezing temperatures for i-$R$-Cd ($R$ = Gd-Tm) deviate from the de Gennes scaling, in a manner consistent with crystal electric field splitting induced local moment anisotropy.Comment: 14 page

Nearly itinerant ferromagnetism in CaNi2 and CaNi3

Single crystals of CaNi2 and CaNi3 were successfully grown out of excess Ca. Both compounds manifest a metallic ground state with enhanced, temperature dependent magnetic susceptibility. The relatively high Stoner factors of Z = 0.79 and Z = 0.87 found for CaNi2 and CaNi3, respectively, reveal their close vicinity to ferromagnetic instabilities. The pronounced field dependence of the magnetic susceptibility of CaNi3 at low temperatures (T < 25 K) suggests strong ferromagnetic fluctuations. A corresponding contribution to the specific heat with a temperature dependence of T^3lnT was also observed.Comment: 6 pages, 7 figures, minor corrections, accepted for publication in PR

Tuning low-temperature physical properties of CeNiGe3 by magnetic field

We have studied the thermal, magnetic, and electrical properties of the ternary intermetallic system CeNiGe3 by means of specific heat, magnetization, and resistivity measurements. The specific heat data, together with the anisotropic magnetic susceptibility, was analyzed on the basis of the point charge model of crystalline electric field. The J=5/2 multiplet of the Ce3+ is split by the crystalline electric field into three Kramers doublets, where the second and third doublets are separated from the first (ground state) doublet by Δ1∼100 K and Δ2∼170 K, respectively. In zero field CeNiGe3 exhibits an antiferromangeic order below TN=5.0 K. For H∥a two metamagnetic transitions are clearly evidenced between 2–4 K from the magnetization isotherm and extended down to 0.4 K from the magnetoresistance measurements. For H∥a, TN shifts to lower temperature as magnetic field increases, and ultimately disappears at Hc∼32.5 kOe. For H\u3eHc, the electrical resistivity shows the quadratic temperature dependence (Δρ=AT2). For H⪢Hc, an unconventional Tn dependence of Δρ with n\u3e2 emerges, the exponent n becomes larger as magnetic field increases. Although the antiferromagnetic phase transition temperature in CeNiGe3 can be continuously suppressed to zero, it provides an example of field tuning that does not match current simple models of quantum criticality

Robust conveniently sealable container for high-temperature single-crystal growth out of reactive melts with high vapor pressure

The high-temperature crystal growth of intermetallics often asks for sealing of the materials in a protective atmosphere. Here, we report on the development of a convenient sealing method for alkali-containing melts, with high vapor pressure and reactivity. Our newly designed container made of high-temperature resistant steel can be sealed manually and reliably without any air exposure of the containing material. The closed container may be heated in air up to at least 1150 ∘C. The containers were applied for the development and optimization of a high-temperature self-flux growth of KFe1-x Ag1+y Ch2 (Ch = Se, Te) single crystals. Their crystal structure and the low-temperature electrical resistance are presented. The successful growths of these air-sensitive materials out of a reactive self-flux confirm the reliability of the container

Magnetic structure of Nd in NdFeAsO studied by x-ray resonant magnetic scattering

The magnetic structure of Nd in NdFeAsO compound has been investigated by x-ray resonant magnetic scattering at the Nd L2 edge (E=6.725 keV) at 1.7≤T≤15 K. At T=1.7 K we find that the Nd moments are aligned along the crystallographic c direction with the (1, 0, 0) propagation vector, and are arranged antiferromagnetically along the a direction and ferromagnetically along the b and c directions. At 1.

Commensurate antiferromagnetic ordering in Ba(Fe{1-x}Co{x})2As2 determined by x-ray resonant magnetic scattering at the Fe K-edge

We describe x-ray resonant magnetic diffraction measurements at the Fe K-edge of both the parent BaFe2As2 and superconducting Ba(Fe0.953Co0.047)2As2 compounds. From these high-resolution measurements we conclude that the magnetic structure is commensurate for both compositions. The energy spectrum of the resonant scattering is in reasonable agreement with theoretical calculations using the full-potential linear augmented plane wave method with a local density functional.Comment: 5 pages, 3 figures; accepted for publication in Phys. Rev. B Rapid Com

High-energy X-ray diffraction studies of i-Sc12Zn88

Although quasicrystals form in a wide variety of ternary and quaternary metallic alloys, examples of stable binary icosahedral quasicrystals are quite rare. Indeed, it has been a decade since the discovery of icosahedral phases in Yb–Cd and Ca–Cd. We have discovered millimeter-sized facetted grains of i-Sc12Zn88 with icosahedral (pentagonal dodecahedral and rhombic triacontahedral) morphologies in solution-grown samples. Structural characterization of the bulk icosahedral phase was accomplished through single-grain high-energy X-ray diffraction. For both growth morphologies, all diffraction peaks could be indexed by a primitive (P-type) icosahedral phase. The two types of morphology do, however, present interesting differences in their respective degrees of quasicrystalline order