SEARCH · Search NASA

Results for “CeNi”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

6 records

All sources NASA NTRS DOE OSTI

DOE OSTI2019

Dynamic magnetic response across the pressure-induced structural phase transition in CeNi

We report that the intermediate-valence compound CeNi experiences a pressure-induced first-order structural phase transition with an abrupt change in the unit cell volume, and as such constitutes an attractive system to study pressure-driven f-electron delocalization behavior in a system with an unstable f-electron shell. The inelastic neutron scattering study of the dynamic magnetic response of CeNi reveals that the structural transition increases the characteristic energy of magnetic fluctuations due to enhanced Ce 4f–Ni 3d hybridization. At the same time, the inelastic 4f magnetic form factor remains unchanged.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

DOE OSTI2017

Materials Data on CeNi by Materials Project

CeNi crystallizes in the orthorhombic Cmcm space group. The structure is three-dimensional. Ce is bonded in a 7-coordinate geometry to seven equivalent Ni atoms. There are a spread of Ce–Ni bond distances ranging from 2.84–3.03 Å. Ni is bonded in a 9-coordinate geometry to seven equivalent Ce and two equivalent Ni atoms. Both Ni–Ni bond lengths are 2.72 Å.

36 MATERIALS SCIENCE↗

DOE OSTI2018

Features of Electronic Structure of Intermetallic Compounds CeNi{sub 4}M (M = Fe, Co, Ni, Cu)

The evolution of the electronic structure of CeNi{sub 4}M (M = Fe, Co, Ni, Cu) intermetallics depending on the type of nickel substitutional impurity is explored. We have calculated band structures of these compounds and considered options of substituting one atom in nickel 3d sublattice in both types of crystallographic positions: 2c and 3g. The analysis of total energy self-consistent calculations has shown that positions of 2c type are more energetically advantageous for single iron and cobalt impurities, whereas a position of 3g type is better for a copper impurity. The Cu substitutional impurity does not change either the nonmagnetic state of ions or the total density at the Fermi level states. Fe and Co impurities, on the contrary, due to their considerable magnetic moments, induce magnetization of 3d states of nickel and cause significant changes in the electronic state density at the Fermi level.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

DOE OSTI2022

Flux Growth of Cerium Nickel Gallides Studied by In Situ Neutron Diffraction

In this work, reactions of cerium and nickel in excess molten gallium were monitored by neutron diffraction during heating and cooling. The formation of binary intermediates CeGa 2 and Ni 2 Ga 3 was observed during heating. During cooling of the molten mixture from 900 °C, precipitation of BaAl 4 -type CeNi 0.74 Ga 3.26 occurred at 850 °C. Upon cooling to 650 °C, this compound reacted in the flux to form Ce 2 NiGa 10 and then Ce 2 NiGa 12 , the latter of which persisted to room temperature. Making use of this information, subsequent reactions were quenched at 750 °C to isolate crystals of CeNi 0.74 Ga 3.26 for further study. Similar reactions replacing Ce with La and quenching above 750 °C yielded LaNi 0.35 Ga 3.65 crystals. Magnetic susceptibility studies on CeNi 0.74 Ga 3.26 indicate that the cerium is trivalent; the Ce 3+ moments undergo a strongly anisotropic ferromagnetic ordering with moment perpendicular to the c axis below 7 K. Heat capacity data show little evidence of heavy fermion behavior. Resistivity measurements show that both LaNi0.35Ga3.65 and CeNi 0.74 Ga 3.26 exhibit metallic behavior. Density of states calculations support this and indicate that Ni/Ga mixing in the compound stabilizes the structure.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2018

Ferromagnetic quantum critical point in CePd 2 P 2 with Pd → Ni substitution

Here, an investigation of the structural, thermodynamic, and electronic transport properties of the isoelectronic chemical substitution series Ce(Pd 1– x Ni x ) 2 P 2 is reported, where a possible ferromagnetic quantum critical point is uncovered in the temperature-concentration ( T–x ) phase diagram. This behavior results from the simultaneous contraction of the unit cell volume, which tunes the relative strengths of the Kondo and Ruderman–Kittel–Kasuya–Yosida (RKKY) interactions, and the introduction of disorder through alloying. Near the critical region at x cr ≈ 0.7, the rate of contraction of the unit cell volume strengthens, indicating that the cerium f valence crosses over from trivalent to a noninteger value. Consistent with this picture, x-ray absorption spectroscopy measurements reveal that while CePd 2 P 2 has a purely trivalent cerium f state, CeNi 2 P 2 has a small (<10 %) tetravalent contribution. In a broad region around x cr , there is a breakdown of Fermi-liquid temperature dependences, signaling the influence of quantum critical fluctuations and disorder effects. Measurements of clean CePd 2 P 2 furthermore show that applied pressure has an initial effect similar to alloying on the ferromagnetic order. From these results, CePd 2 P 2 emerges as a keystone system to test theories such as the Belitz-Kirkpatrick-Vojta model for ferromagnetic quantum criticality, where distinct behaviors are expected in the dirty and clean limits.

36 MATERIALS SCIENCE↗

DOE OSTI2021

RR Lyrae Stars in the Newly Discovered Ultra-faint Dwarf Galaxy Centaurus I*

We report the detection of three RR Lyrae (RRL) stars (two RRc and one RRab) in the ultra-faint dwarf (UFD) galaxy Centaurus I (Cen I) and two Milky Way (MW) δ Scuti/SX Phoenicis stars based on multi-epoch giz DECam observations. The two RRc stars are located within two times the half-light radius (r $_{h}$) of Cen I, while the RRab star (CenI-V3) is at ∼6 r $_{h}$. The presence of three distant RRL stars clustered this tightly in space represents a 4.7σ excess relative to the smooth distribution of RRL in the Galactic halo. Using the newly detected RRL stars, we obtain a distance modulus to Cen I of μ $_{0}$ = 20.354 ± 0.002 mag (σ = 0.03 mag), a heliocentric distance of D $_{⊙}$ = 117.7 ± 0.1 kpc (σ = 1.6 kpc), with systematic errors of 0.07 mag and 4 kpc. The location of the Cen I RRL stars in the Bailey diagram is in agreement with other UFD galaxies (mainly Oosterhoff II). Finally, we study the relative rate of RRc+RRd (RRcd) stars (f $_{cd}$) in UFD and classical dwarf galaxies. The full sample of MW dwarf galaxies gives a mean of f $_{cd}$ = 0.28. While several UFD galaxies, such as Cen I, present higher RRcd ratios, if we combine the RRL populations of all UFD galaxies, the RRcd ratio is similar to the one obtained for the classical dwarfs (f $_{cd}$ ∼ 0.3). Therefore, there is no evidence for a different fraction of RRcd stars in UFD and classical dwarf galaxies.

79 ASTRONOMY AND ASTROPHYSICS↗