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Title: Nickel deficiency in RENi2-xP2 (RE=La, Ce, Pr). Combined crystallographic and physical property studies

Abstract

Large single crystals from RENi{sub 2-x}P{sub 2} (RE = La, Ce, Pr) were synthesized from the pure elements using Sn as a metal flux, and their structures were established by X-ray crystallography. The title compounds were confirmed to crystallize in the body-centered tetragonal ThCr{sub 2}Si{sub 2} structure type (space group I4/mmm (No. 139); Pearson's symbol tI10), but with a significant stoichiometry breadth with respect to the transition metal. Systematic synthetic work, coupled with accurate structure refinements indicated strong correlation between the degree of Ni-deficiency and the reaction conditions. For four different PrNi{sub 2-x}P{sub 2} (x {le} 0.5) samples, temperature dependent dc magnetization measurements indicated typical local moment 4f-magnetism and a stable Pr{sup 3+} ground state. Field-dependent heat capacity data confirmed a ferromagnetic order at low temperature, and the variations of T{sub c} with the concentration of Ni defects are discussed. LaNi{sub 2-x}P{sub 2}, as expected was found to be Pauli-like paramagnetic in the studied temperature regime, while the Ce-analog CeNi{sub 2-x}P{sub 2} (x = 0.28(1)) showed the characteristics of a mixed valent Ce{sup 3+}/Ce{sup 4+} system with a possible Kondo temperature on the order of 230 K.

Authors:
 [1];  [1];  [1];  [1];  [2];  [2]
  1. Los Alamos National Laboratory
  2. U. OF DE
Publication Date:
Research Org.:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
962290
Report Number(s):
LA-UR-08-07752; LA-UR-08-7752
Journal ID: ISSN 0022-4596; JSSCBI; TRN: US200919%%54
DOE Contract Number:
AC52-06NA25396
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Solid State Chemistry
Country of Publication:
United States
Language:
English
Subject:
36; CRYSTALLOGRAPHY; DEFECTS; GROUND STATES; MAGNETIZATION; MONOCRYSTALS; NICKEL; SPECIFIC HEAT; STOICHIOMETRY; TRANSITION ELEMENTS

Citation Formats

Bauer, Eric D, Ronning, Filip, Thompson, Joe D, Sarrao, John L, Bobev, S, and Xia, S. Nickel deficiency in RENi2-xP2 (RE=La, Ce, Pr). Combined crystallographic and physical property studies. United States: N. p., 2008. Web.
Bauer, Eric D, Ronning, Filip, Thompson, Joe D, Sarrao, John L, Bobev, S, & Xia, S. Nickel deficiency in RENi2-xP2 (RE=La, Ce, Pr). Combined crystallographic and physical property studies. United States.
Bauer, Eric D, Ronning, Filip, Thompson, Joe D, Sarrao, John L, Bobev, S, and Xia, S. Tue . "Nickel deficiency in RENi2-xP2 (RE=La, Ce, Pr). Combined crystallographic and physical property studies". United States. doi:. https://www.osti.gov/servlets/purl/962290.
@article{osti_962290,
title = {Nickel deficiency in RENi2-xP2 (RE=La, Ce, Pr). Combined crystallographic and physical property studies},
author = {Bauer, Eric D and Ronning, Filip and Thompson, Joe D and Sarrao, John L and Bobev, S and Xia, S},
abstractNote = {Large single crystals from RENi{sub 2-x}P{sub 2} (RE = La, Ce, Pr) were synthesized from the pure elements using Sn as a metal flux, and their structures were established by X-ray crystallography. The title compounds were confirmed to crystallize in the body-centered tetragonal ThCr{sub 2}Si{sub 2} structure type (space group I4/mmm (No. 139); Pearson's symbol tI10), but with a significant stoichiometry breadth with respect to the transition metal. Systematic synthetic work, coupled with accurate structure refinements indicated strong correlation between the degree of Ni-deficiency and the reaction conditions. For four different PrNi{sub 2-x}P{sub 2} (x {le} 0.5) samples, temperature dependent dc magnetization measurements indicated typical local moment 4f-magnetism and a stable Pr{sup 3+} ground state. Field-dependent heat capacity data confirmed a ferromagnetic order at low temperature, and the variations of T{sub c} with the concentration of Ni defects are discussed. LaNi{sub 2-x}P{sub 2}, as expected was found to be Pauli-like paramagnetic in the studied temperature regime, while the Ce-analog CeNi{sub 2-x}P{sub 2} (x = 0.28(1)) showed the characteristics of a mixed valent Ce{sup 3+}/Ce{sup 4+} system with a possible Kondo temperature on the order of 230 K.},
doi = {},
journal = {Journal of Solid State Chemistry},
number = ,
volume = ,
place = {United States},
year = {Tue Jan 01 00:00:00 EST 2008},
month = {Tue Jan 01 00:00:00 EST 2008}
}
  • Large single crystals from RENi{sub 2-x}P{sub 2} (RE=La, Ce, Pr) were synthesized from the pure elements using Sn as a metal flux, and their structures were established by X-ray crystallography. The title compounds were confirmed to crystallize in the body-centered tetragonal ThCr{sub 2}Si{sub 2} structure type (space group I4/mmm (No. 139); Pearson's symbol tI10), but with a significant homogeneity range with respect to the transition metal. Systematic synthetic work, coupled with accurate structure refinements indicated strong correlation between the degree of Ni-deficiency and the reaction conditions. According to the temperature dependent dc magnetization measurements, LaNi{sub 2-x}P{sub 2} (x=0.30(1)), as expected,more » is Pauli-like paramagnetic in the studied temperature regime, while the Ce-analog CeNi{sub 2-x}P{sub 2} (x=0.28(1)) shows the characteristics of a mixed valent Ce{sup 3+}/Ce{sup 4+} system with a possible Kondo temperature scale on the order of 1000 K. For three different PrNi{sub 2-x}P{sub 2} (x<=0.5) samples, the temperature and field dependence of the magnetization indicated typical local moment 4f-magnetism and a stable Pr{sup 3+} ground state, with subtle variations of T{sub C} as a function of the concentration of Ni defects. Field-dependent heat capacity data for CeNi{sub 2-x}P{sub 2} (x=0.28(1)) and PrNi{sub 2-x}P{sub 2} (x=0.53(1)) are discussed as well. - Graphical abstract: The non-stoichiometric RENi{sub 2-x}P{sub 2} phases (RE=La, Ce, Pr), whose average structure belongs to the ThCr{sub 2}Si{sub 2} type, are shown to exist with a wide range of defects on the transition metal site. The changes in the Ni-underoccupancy affect the magnetism of the synthesized materials.« less
  • Four members of the RE{sub 4}LiGe{sub 4} (RE=La, Ce, Pr, and Sm) system have been prepared by high-temperature reaction method and characterized by X-ray diffractions. All compounds crystallize in the orthorhombic Gd{sub 5}Si{sub 4}-type structure (space group Pnma, Pearson code oP16) with bonding interactions for interslab Ge{sub 2} dimers. The Li substitution for rare-earth elements in the RE{sub 4}LiGe{sub 4} system leads to a combined effect of the increased chemical pressure and the decreased valance electron concentration (VEC), which eventually results in the structure transformation from the Sm{sub 5}Ge{sub 4}-type with all broken interslab Ge–Ge bond for the parental RE{submore » 5}Ge{sub 4} to the Gd{sub 5}Si{sub 4}-type structure for the ternary RE{sub 4}LiGe{sub 4} (RE=La, Ce, Pr, and Sm) system. Site-preference between rare-earth metals and Li is proven to generate energetically the most favorable atomic arrangements according to coloring-problem, and the rationale is provided using both the size-factor and the electronic-factor related, respectively, to site-volume and electronegativity as well as QVAL values. Tight-binding, linear-muffin-tin-orbital (TB-LMTO) calculations are performed to investigate electronic densities of states (DOS) and crystal orbital Hamilton population (COHP) curves. The influence of reduced VEC for chemical bonding including the formation of interslab Ge{sub 2} dimers is also discussed. The magnetic property measurements prove that the non-magnetic Li substitution leads to the ferromagnetic (FM)-like ground state for Ce{sub 4}LiGe{sub 4} and the co-existence of antiferromagntic (AFM) and FM ground states for Sm{sub 4}LiGe{sub 4}. - Graphical abstract: Reported is a combined effect of the chemical pressure and the reduced VEC caused by the smaller monovalent non-magnetic Li substitution for the larger trivalent magnetic rare-earth metals in the RE{sub 4}LiGe{sub 4} (RE=La, Ce, Pr, and Sm) system. This results in the structure transformation from the Sm{sub 5}Ge{sub 4}-type to the Gd{sub 5}Si{sub 4}-type structure and the changes in magnetic properties. Display Omitted - Highlights: • Four Li-containing intermetallic compounds RE{sub 4}LiGe{sub 4} (RE=La, Ce, Pr and Sm) were synthesized. • The combined effect of the chemical pressure and the reduced VEC caused by Li substitution for a rare-earth metal results in the structure transformation. • Electronic structures and magnetic properties of title compounds were thoroughly investigated.« less
  • This paper reports the crystal structure of Ce{sub 3}B{sub 2}N{sub 4} (space group Immm, a = 0.35653(5) nm,b = 0.63160(21) nm,c = 1.07131(50) nm) was derived from X-ray powder photographs; precise atom parameters, atom occupancies, atom order, and interatomic distances obtained from room-temperature neutron powder diffraction data employing the Rietveld profile analysis method. The final reliability values of the refinement were R{sub F} = 0.059 and R{sub 1} = 0.068. Boron atoms in triangular prismatic metal coordination (Ce{sub 6}B) are at a distance of 0.1785(7) nm and form pairs. In a tetrakaidecahedral surrounding (Ce{sub 6}B)BN{sub 2}, each boron atom formsmore » single bonds with two nitrogen atoms at a distance of 0.1464(4) nm. Nitrogen atoms thus are in rectangular pyramidal metal coordination (Ce{sub 5}N) with one additional boron atom completing a distorted octahedron (Ce{sub 5}BN).« less
  • Six quaternary rare-earth-containing sulphides RE{sub 3}MInS{sub 7} (M=Fe, Co, Ni) have been prepared by reactions of the elements at 1050–1150 °C. They are the first examples of chalcogenides RE{sub 3}MM'Ch{sub 7} adopting related La{sub 3}CuSiS{sub 7}- or ordered Ce{sub 3}Al{sub 1.67}S{sub 7}-type structures in which the M' component is indium. They crystallize in the noncentrosymmetric hexagonal space group P6{sub 3} with Z=2 and cell parameters in the ranges of a=9.95–10.15 Å and c=6.25–6.29 Å for RE{sub 3}FeInS{sub 7} (RE=La–Pr), RE{sub 3}CoInS{sub 7} (RE=La, Ce), and La{sub 3}NiInS{sub 7}. The crystal structure consists of parallel chains of face-sharing M-centred octahedra andmore » stacks of In-centred tetrahedra, all pointing in the same polar direction, with seven-coordinate La atoms in the intervening spaces. X-ray photoelectron spectra support the valence assignments implied by the formulation (RE{sup 3+}){sub 3}(M{sup 2+})(In{sup 3+})(S{sup 2−}){sub 7}. Magnetic measurements are suggestive of antiferromagnetic coupling between the M moments. Band structure calculations reveal that a band gap of 0.25 eV is present in La{sub 3}FeInS{sub 7}, whereas the increased electron count in La{sub 3}CoInS{sub 7} and La{sub 3}NiInS{sub 7} causes the Fermi level to cut narrow bands. - Graphical abstract: RE{sub 3}MInS{sub 7} (M=Fe, Co, Ni) consists of chains of face-sharing M-centred octahedra and stacks of In-centred tetrahedra. - Highlights: • Six members of noncentrosymmetric sulphide series RE{sub 3}MInS{sub 7} have been prepared. • They are the first examples of chalcogenides RE{sub 3}MM'Ch{sub 7} with In atoms in M' site. • X-ray photoelectron spectra support the formulation (RE{sup 3+}){sub 3}(M{sup 2+})(In{sup 3+})(S{sup 2−}){sub 7}. • Band structure calculations suggest semiconducting or metallic behaviour.« less
  • Investigations on phase relationships and crystal structures have been conducted on several ternary rare-earth titanium antimonide systems. The isothermal cross-sections of the ternary RE-Ti-Sb systems containing a representative early (RE=La) and late rare-earth element (RE=Er) have been constructed at 800 deg. C. In the La-Ti-Sb system, the previously known compound La{sub 3}TiSb{sub 5} was confirmed and the new compound La{sub 2}Ti{sub 7}Sb{sub 12} (own type, Cmmm, Z=2, a=10.5446(10) A, b=20.768(2) A, and c=4.4344(4) A) was discovered. In the Er-Ti-Sb system, no ternary compounds were found. The structure of La{sub 2}Ti{sub 7}Sb{sub 12} consists of a complex arrangement of TiSb{sub 6}more » octahedra and disordered fragments of homoatomic Sb assemblies, generating a three-dimensional framework in which La atoms reside. Other early rare-earth elements (RE=Ce, Pr, Nd) can be substituted in this structure type. Attempts to prepare crystals in these systems through use of a tin flux resulted in the discovery of a new Sn-containing pseudoternary phase RETi{sub 3}(Sn{sub x}Sb{sub 1-x}){sub 4} for RE=Nd, Sm (own type, Fmmm, Z=8; a=5.7806(4) A, b=10.0846(7) A, and c=24.2260(16) A for NdTi{sub 3}(Sn{sub 0.1}Sb{sub 0.9}){sub 4}; a=5.7590(4) A, b=10.0686(6) A, and c=24.1167(14) A for SmTi{sub 3}(Sn{sub 0.1}Sb{sub 0.9}){sub 4}). Its structure consists of double-layer slabs of Ti-centred octahedra stacked alternately with nets of the RE atoms; the Ti atoms are arranged in kagome nets. - Graphical abstract: La{sub 2}Ti{sub 7}Sb{sub 12} contains sectioned layers consisting of Ti-centred octahedra linked by corner- and face-sharing.« less