M.B. Tchoula Tchokonté

Specific heat, susceptibility, magnetotransport and thermoelectric power of the Kondo alloys (Ce1-xLax)Cu5In

The influence of substituting Ce with La in the Kondo compound CeCu5In has been investigated using x-ray diffraction, specific heat (Cp), electrical resistivity (?(T)), magnetoresistivity?(MR) and thermoelectric power?(TEP) measurements. Cp of CeCu5In and the (Ce1?xLax)Cu5In alloys shows enhanced values at low temperatures. Between?10 and 20?K the equation Cp/T = ?conv+?T2 fits the data for all alloys with ?conv scaling linearly with Ce concentration. Below 10?K a pronounced upturn in Cp values occurs. Susceptibility data above 100?K follow the Curie?Weiss relation and give effective moment ?eff values in fair agreement with that of a Ce3+-ion. The ?(T) studies illustrate the evolution from Kondo lattice to single-ion Kondo behaviour with increase in La content in the (Ce1?xLax)Cu5In alloy series. MR measurements on Ce dilute alloys are interpreted within the single-ion Bethe ansatz description and values of the Kondo temperature TK are calculated. A compressible Kondo lattice model has been used to describe the decrease in TK and in Tm? (the temperature at which a maximum in ?(T) occurs for the coherent dense Kondo alloys) with decrease in Ce concentration for these alloys. The TEP is positive and shows a maximum at approximately 45?K for several investigated (Ce1?xLax)Cu5In alloys.

Magnetic and electrical properties of the Kondo system CePt2(Si1−xGex)2

Magnetic susceptibility X(T), electrical resistivity ρ(T) and magnetoresistivity of CePt 2 (Si 1-x Ge x ) 2 alloys (0 ≤ x < 1) are reported. For X(T) of these, the Curie-Weiss relationship is followed with effective moments in close agreement with μ eff = 2.54 μ B expected for Ce 3+ . A maximum in ρ(T) is observed at a temperature T max ∼ T K ∼ exp(-1/|JN(E F )|). From the decrease in T max with increasing x it is deduced that |JN(E F )| x=0 = 0.11 ± 0.02.

Kondo behaviour of Ce1−xLaxCu5In and CeCu5In1−xMx (M=Al or Ga)

Abstract Electrical resistivity ρ(T) measurements for compounds of the Ce1−xLaxCu5In and CeCu5In1−xMx (M=Al or Ga) series indicate the evolution from coherent Kondo to incoherent Kondo behaviour as x is increased. The magnetic susceptibility of the compounds follows a Curie–Weiss relation.

Electrical and thermodynamics properties of RE8Pd24Sn

We report on X-ray diffraction, the electrical resistivity (ρ(T)), the magnetic susceptibility (χ(T)), the magnetization (σ(μ0H)) and the heat capacity (Cρ(T)) of the alloy system RE8Pd24Sn (RE = Pr, Nd, Gd, Tb, Dy, Ho, Er and Tm) which has the cubic AuCu3-type structure. Compounds with RE = Gd and Tb order magnetically: Gd8Pd24Sn exhibits two magnetic transitions observed in its χ(T) and ρ(T) whereas Tb8Pd24Sn exhibits only one magnetic transition observed in its χ(T). Measurements of ρ(T) of the Gd and Tb compounds indicate a minimum above TN. χ(T) of all compounds follows the Curie-Weiss behaviour with high-temperature effective moment values close to that expected for the free RE3+ -ion. σ(μ0H) measurements taken at 1.7 K are presented for all members of the RE8Pd24Sn system. Metamagnetic behaviour is observed for Tb8Pd24Sn. Cρ results for the Gd and Tb compounds confirm the magnetic ordering indicated by the χ(T) and ρ(T) studies. In the paramagnetic region Cρ/T = γ + βT2 for both the Gd and Tb comprounds.