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

TitleStructural, thermal, magnetic, and electronic transport properties of the LaNi2(Ge1-xPx)(2) system
Publication TypeJournal Article
Year of Publication2012
AuthorsGoetsch RJ, Anand VK, Pandey A, Johnston DC
Journal TitlePhysical Review B
Date Published02
Type of ArticleArticle
ISBN Number1098-0121
Accession NumberWOS:000300931900005
Keywordsbloch-gruneisen function, ceni2ge2, crystal-structure, earth, HEAT-CAPACITY, lani2ge2, lanthanoid-nickel-phosphides, layered, mgb2 superconductor, quaternary compound, thcr2si2 type-structure

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 C-p, magnetic susceptibility chi, and electrical resistivity rho 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 rho(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 C-p measurements yield a rather large Sommerfeld electronic specific heat coefficient gamma = 12.4(2) mJ/mol K-2 for x = 0, reflecting a large density of states at the Fermi energy that is comparable with the largest values found for the AFe(2)As(2) class of materials with the same crystal structure. The gamma decreases approximately linearly with x to 7.4(1) mJ/mol K-2 for x = 1. The chi measurements show nearly temperature-independent paramagnetic behavior across the entire range of compositions except for LaNi2Ge2, where a broad peak is observed at approximate to 300 K from chi(T) measurements up to 1000 K that may arise from short-range antiferromagnetic correlations in a quasi-two-dimensional magnetic system. High-accuracy Pade approximants representing the Debye lattice heat capacity and Bloch-Gruneisen electron-phonon resistivity functions versus T are presented and are used to analyze our experimental C-p(T) and rho(T) data, respectively, for 1.8 K <= T <= 300 K. The T dependences of rho for all samples are well-described over this T range by the Bloch-Gruneisen model, although the observed rho(300 K) values are larger than calculated from this model. A significant T dependence of the Debye temperature determined from the C-p(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.

URL<Go to ISI>://WOS:000300931900005
Alternate JournalPhys. Rev. B