R.A. Gordon

Magnetic properties of several Ce2T2M phases with T=Ni, Pd and M=In, Sn, Pb

Abstract Four new ternary intermetallic compounds were prepared: Ce 2 Pd 2 In, Ce 2 Pd 2 Sn, Ce 2 Pd 2 Pb and Ce 2 Ni 2 Sn. The first three are isotypic, adopting the tetragonal U 3 Si 2 structure. The structure of Ce 2 Ni 2 Sn is of the orthorhombic Mo 2 CoB 2 type, but extensive solid solutions occur between it and Ce 2 Pd 2 Sn. Magnetic susceptibility measurements were performed on each ternary and the known Ce 2 Ni 2 In phase. Cerium is tetravalent in Ce 2 Ni 2 In and trivalent in the remaining phases at room temperature. Kondo behaviour is present in Ce 2 Ni 2 Sn with T K near 9 K. Ferromagnetic behaviour with T c near 4.2 K is seen in both Ce 2 Pd 2 In and Ce 2 Pd 2 Sn. Anti-ferromagnetic ordering is observed in Ce 2 Pd 2 Pb with a Neel temperature of 6.2 K. An apparently second-order transition involving a reduction in the effective cerium moment also occurs in Ce 2 Pd 2 Pb at 120 K.

Substitution in Ce2TSi3 intermetallic compositions with T = (Cr, Mn, Fe, Co, or Ni)x(Pd or Au)1−x

Abstract Alloys of composition Ce 2 (3d/T)Si 3 , with 3d one of Cr, Mn, Fe, Co or Ni and T being Pd or Au, were prepared and examined by powder X-ray diffraction. Select single phase compositions were further examined by magnetic susceptibility, by resistivity for the Pd and Co end-members, and by specific heat for Ce 2 CoSi 3 . For compounds not containing cobalt, effective cerium moments consistent with trivalent cerium were observed. A re-examination of the AlB 2 related structure of Ce 2 CoSi 3 by single crystal methods revealed ordering of cobalt within the CoSi 3 hexagonal layer. Magnetic susceptibility, resistance and specific heat measurements suggest valence fluctuation behavior of the cerium in Ce 2 CoSi 3 . A return to trivalent cerium magnetic behavior occurs on increasing the palladium or gold substitution for cobalt.

Electric and magnetic behaviour of Ce8Pd24M compounds with M(Ga, In, Sn, Pb, Sb and Bi)

Abstract We have prepared and examined the resistivity and magnetic susceptibility of a series of ternary compounds with composition Ce 8 Pd 24 M, where M is one of Ga, In, Sn, Sb, Pb or Bi, and the related composition La 8 Pd 24 In. All members of this series are cubic with effective cerium moments consistent with trivalent cerium. The lanthanum compound behaves as a simple metal in resistivity and has a small, negative susceptibility at 295 K. All the cerium compounds but the gallide exhibit antiferromagnetic ordering below 10 K. Metallic behaviour is observed for all. The properties of the stannide, plumbide, antimonide and bismuthide reflect some weak interactions with crystal-field-split cerium states above 30 K and changes in slope at low temperature coincident with the second-order antiferromagnetic phase transitions. Resistivities for the gallide and indide display broad features near 15 and 50 K, respectively, suggesting that a strong Kondo interaction is present in these materials.

Crystal structure and physical properties of Ce3Pd6Sb5

Abstract A new ternary antimonide, Ce 3 Pd 6 Sb 5 , was prepared by arc melting of the elemental components and subsequent annealing at 750°C. Its orthorhombic crystal structure was determined from single-crystal X-ray data: space group, Pmmn ; Z = 2; a = 1348.1(2) pm, b = 445.9(1) pm and c = 1005.0(1) pm; V = 0.6041(2) nm 3 , wR 2 = 0.045; 1432 F 2 values; 48 variables. The structure of Ce 3 Pd 6 Sb 5 is of a new type, built from three pseudo-body-centered subcells of the cerium atoms. Palladium and antimony atoms form a three-dimensional infinite polyanion [Pd 6 Sb 5 ] with an atomic arrangement derived from the well-known ThCr 2 Si 2 and CaBe 2 Ge 2 structures. The crystal chemistry of this new compound is discussed together with the related Dy 3 Co 6 Sn 5 -type structure. The magnetic susceptibility exhibits significant anisotropy with an effective high temperature moment per cerium of 2.67 μ B and antiferromagnetic ordering at 6 K. The resistance shows a minimum near 17 K, possibly suggesting some Kondo-type interactions, and an anomaly at 6 K which corresponds to the antiferromagnetic ordering.

Magnetic behavior of new CePdSn ternary compounds

Abstract We have prepared and measured the magnetic susceptibility of several new ternary compounds in the CePdSn system: CePd0.5Sn2, Ce8Pd24Sn, “Ce4Pd7Sn4” and the solid solution based on Ce2Pd2Sn. In CePd0.5Sn2, an effective magnetic moment of 2.60(3)μB is observed but no ordering is apparent above 4.2 K. Complete nickel substitution for Pd in Ce(Pd1−xNix)0.5Sn2 results in the known lower limit to the CeNi1−xSn2 solid solution. We have determined the extent of the solid solution based on Ce2Pd2Sn to have the form Ce4Pd4+2xSn2−x−y in a roughly triangular region with limits of x = 0, y = 0; x = 0, y ≈ 2 3 and x ≈ 2 3 , y = 0. Magnetic behavior consistent with trivalent cerium moments is observed at these limits with ferromagnetic ordering present for x = 0, y = 2 3 . Cubic Ce8Pd24Sn has an effective high temperature moment of 2.49(4)μB and antiferromagnetic ordering at 7.5 K. A hexagonal phase dominates the composition “Ce4Pd7Sn4”, but a structural solution has remained elusive. An effective cerium moment of 2.53(4)μB is observed in “Ce4Pd7Sn4” with a Weiss constant of −23 K, suggesting antiferromagnetic interactions, but no ordering is observed above 4.2 K.

Crystal Structure and Magnetic Susceptibility of Ce8Pd24Sb

Abstract The ternary compound Ce8Pd24Sb is very close in composition to the intermediate valent binary CePd3. A single crystal study yielded a cubic cell with a = 8.461 (1)Å, Pm3̄m symmetry with wR2 = 0.0412 based on 1453 reflections (222 unique) and 16 parameters. This new structure type is composed of distorted perovskite and Cu3Au subcells arranged with the perovskite-like units centred on the corners of the cube. Fitting the magnetic susceptibility data above 100K to a Curie-Weiss expression yielded a Weiss constant of -15(3)K (antiferromagnetic) and an effective high temperature moment per cerium of 2.45(4)/μв indicating trivalent cerium. No ordering was observerd above 3K.

Magnetic behaviour of two AlB2-related germanides: CePd0.63Ge1.37 and CeAu0.75Ge1.25

Abstract The title compounds were prepared from the elemental components by arc-melting and subsequent annealing at 1020 K and 1170 K. Both CePd 0.63 Ge 1.37 and CeAu 0.75 Ge 1.25 crystallize in the AlB 2 structure type with a statistical distribution of the transition metal and germanium atoms on the boron site. The structure of CeAu 0.75 Ge 1.25 was refined from single crystal X-ray data: P6/mmm, a =433.5(1) pm, c =422.6(1) pm, V =0.0688(1) nm 3 , Z =1, wR 2=0.0504 for 157 F 2 values and 7 variables. Magnetic susceptibility data for both compounds show a full cerium moment and ferromagnetic ordering at 6.0(5) K for CeAu 0.75 Ge 1.25 and 3.0(5) K for CePd 0.63 Ge 1.37 . The crystal structure and properties of CeAu 0.75 Ge 1.25 are compared with those of equiatomic CeAuGe which adopts the NdPtSb structure type, an ordered variant of AlB 2 .

Crystal structure, electric and magnetic behaviour of Ce2Pd9Sb3

A new ternary compound in the Ce–Pd–Sb system has been observed and studied by single-crystal diffraction, magnetic susceptibility and resistivity. This new compound, Ce2Pd9Sb3, was determined to crystallize in the Y2Co3Ga9 structure type: Cmcm, a, = 13.769(2)A, b= 8.0412(8)A, c= 9.348(1)A, wR2 = 6.7%, 709 F2 values and 42 variables. An anti-site relationship exists between the p block and transition elements relative to the parent structure type. The magnetic susceptibility exhibits Curie–Weiss behaviour with an effective cerium moment of 2.51(3)µB, comparable to the free ion value of 2.54 µB and negligible exchange [θ= 2(2) K]. No ordering of moments is observed above 4.2 K. Resistivity measurements indicate simple metallic behaviour with no apparent evidence for interaction between the local cerium moments and conduction electrons.

Physical properties of CePd3As2

Abstract CePd 3 As 2 was prepared from the elements by first melting the reactants at 850°C and subsequent annealing of a pressed pellet at 750°C. It adopts the monoclinic ( C 2/ m ) structure of GdPd 3 As 2 , as confirmed by a single crystal X-ray study, with a = 1667.3(2) pm, b = 412.05(4) pm, c = 999.8(1) pm, β = 108.045(4)°. Magnetic susceptibility measurements indicate trivalent cerium moments of 2.46(3) μ B and suggest some weak anti-ferromagnetic exchange (θ = −11(2) K). No apparent magnetic ordering is observed in the magnetic susceptibility. Resistance measurements indicate metallic behavior with a decrease in magnetic scattering below 100 K arising from thermal depopulation of cerium crystal field levels.