High-resolution x-ray diffraction study of the heavy-fermion compound YbBiPt

YbBiPt is a heavy-fermion compound possessing significant short-range antiferromagnetic correlations below a temperature of $T^{\textrm{*}}=0.7$ K, fragile antiferromagnetic order below $T_{\rm{N}}=0.4$ K, a Kondo temperature of $T_{\textrm{K}} \approx1$ K, and crystalline-electric-field splitting on the order of $E/k_{\textrm{B}}=1\,\textrm{-}\,10$ K. Whereas the compound has a face-centered-cubic lattice at ambient temperature, certain experimental data, particularly those from studies aimed at determining its crystalline-electric-field scheme, suggest that the lattice distorts at lower temperature. Here, we present results from high-resolution, high-energy x-ray diffraction experiments which show that, within our experimental resolution of $\approx6\,\textrm{-}\,10\times10^{-5}$ \AA, no structural phase transition occurs between $T=1.5$ and $50$ K. In combination with results from dilatometry measurements, we further show that the compound's thermal expansion has a minimum at $\approx18$ K and a region of negative thermal expansion for $9<T<18$ K. Despite diffraction patterns taken at $1.6$ K which indicate that the lattice is face-centered cubic and that the Yb resides on a crystallographic site with cubic point symmetry, we demonstrate that the linear thermal expansion may be modeled using crystalline-electric-field level schemes appropriate for Yb$^{3+}$ residing on a site with either cubic or less than cubic point symmetry.Comment: 7 pages, 3 figures, submitted to Phys. Rev.

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

Anisotropic transport and magnetic properties, and magnetic-field tuned states of CeZn11 single crystals

We present detailed temperature and field dependent data obtained from magnetization, resistivity, heat capacity, Hall resistivity and thermoelectric power measurements performed on single crystals of CeZn11. The compounds orders antiferromagnetically at $\sim$ 2 K. The zero-field resistivity and TEP data show features characteristic of a Ce-based intermetallic with crystal electric field splitting and possible correlated, Kondo lattice effects. We constructed the T-H phase diagram for the magnetic field applied along the easy, [110], direction which shows that the magnetic field required to suppress T_N below 0.4 K is in the range of 45-47.5 kOe. A linear behavior of the rho(T) data, H||[110], was observed only for H=45 kOe for 0.46 K<T<1.96 K followed by the Landau-Fermi-liquid regime for a limited range of fields, 47.5 kOe< H<60 kOe. From the analysis of our data, it appears that CeZn11 is a weakly to moderately correlated local moment compound with rather small Kondo temperature. The thermoelectric and transport properties of CeZn11 are mostly governed by the CEF effects. Given the very high quality of our single crystals, quantum oscillations are found for both CeZn11 and its non-magnetic analogue, LaZn11

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.

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