title: Synthesis, structural characterization, and physical properties of the early rare-earth metal digermanides REGe(2-x) (x ≈ 1/4) [RE = La-Nd, Sm]. A case study of commensurately and incommensurately modulated structures.
abstract: Rare-earth metal germanides with the general formula RE(4)Ge(7) (RE = La, Ce, Pr, Nd, Sm) have been synthesized using the In-flux technique. Their structures have been established from single-crystal and powder X-ray diffraction, and the structural elucidation has been aided by electron diffraction. These compounds represent superstructures of the α-ThSi(2) structure type through the long- and/or short-range vacancy ordering. RE(4)Ge(7) (RE = Pr, Nd, Sm) appear to be commensurately modulated 4-fold superstructure of REGe(2-x) (x = 1/4), while coexistence of commensurate and incommensurate modulation is revealed in the La- and Ce-analogues. These results shed more light on the structural evolution of the REGe(2-x) phases as function of the vacancy concentration and nature of the rare-earth metal. Measurements of the magnetic susceptibilities on well-characterized single-crystals show ferromagnetic, antiferromagnetic, and even spin-glass-like behaviors. Mean-field theory is used to evaluate the correlations between structural and magnetic property data. Measurements on the electrical resistivities and the heat capacities are also presented and discussed.
authors.affiliation: Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware 19716, United States.
authors.forename: Jiliang
authors.initials: J
authors.lastname: Zhang
authors.forename: Paul H
authors.initials: PH
authors.lastname: Tobash
authors.forename: William D
authors.initials: WD
authors.lastname: Pryz
authors.forename: Douglas J
authors.initials: DJ
authors.lastname: Buttey
authors.forename: Namjung
authors.initials: N
authors.lastname: Hur
authors.forename: Joe D
authors.initials: JD
authors.lastname: Thompson
authors.forename: John L
authors.initials: JL
authors.lastname: Sarrao
authors.forename: Svilen
authors.initials: S
authors.lastname: Bobev