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Title: Structural, thermal, magnetic, and electronic transport properties of the LaNi₂(Ge1-xPx)₂ system

Polycrystalline samples of LaNi₂(Ge1-xPx)₂ (x=0,0.25,0.50,0.75,1) were synthesized and their properties investigated by x-ray diffraction (XRD) measurements at room temperature and by heat capacity Cp, magnetic susceptibility χ, and electrical resistivity ρ measurements versus temperature T from 1.8 to 350 K. Rietveld refinements of powder XRD patterns confirm that these compounds crystallize in the body-centered-tetragonal ThCr₂Si₂-type structure (space group I4/mmm) with composition-dependent lattice parameters that slightly deviate from Vegard's law. The ρ(T) measurements showed a positive temperature coefficient for all samples from 1.8 to 300 K, indicating that all compositions in this system are metallic. The low-T Cp measurements yield a rather large Sommerfeld electronic specific heat coefficient γ=12.4(2) mJ/mol K² for x=0, reflecting a large density of states at the Fermi energy that is comparable with the largest values found for the AFe₂As₂ class of materials with the same crystal structure. The γ decreases approximately linearly with x to 7.4(1) mJ/mol K² for x=1. The χ measurements show nearly temperature-independent paramagnetic behavior across the entire range of compositions except for LaNi₂Ge₂, where a broad peak is observed at ≈300 K from χ(T) measurements up to 1000 K that may arise from short-range antiferromagnetic correlations in a quasi-two-dimensional magnetic system. High-accuracymore » Padé approximants representing the Debye lattice heat capacity and Bloch-Grüneisen electron-phonon resistivity functions versus T are presented and are used to analyze our experimental Cp(T) and ρ(T) data, respectively, for 1.8K≤T≤300 K. The T dependences of ρ for all samples are well-described over this T range by the Bloch-Grüneisen model, although the observed ρ(300 K) values are larger than calculated from this model. A significant T dependence of the Debye temperature determined from the Cp(T) data was observed for each composition. No clear evidence for bulk superconductivity or any other long-range phase transition was found for any of the LaNi₂(Ge1-xPx)₂ compositions studied.« less
Authors:
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Publication Date:
OSTI Identifier:
1099267
Type:
Publisher's Accepted Manuscript
Journal Name:
Physical Review. B, Condensed Matter and Materials Physics
Additional Journal Information:
Journal Volume: 85; Journal Issue: 5; Journal ID: ISSN 1098-0121
Publisher:
American Physical Society
Sponsoring Org:
USDOE
Country of Publication:
United States
Language:
English