Heavy Fermi and non-Fermi liquid behavior, superconductivity, and magnetism inf-electron metals

Measurements of the low temperature specific heat C, magnetic susceptibility χ, and the electrical resistivity ρ of the U_1−x Y_xPd₂Al₃ system reveal non-Fermi liquid (NFL) behavior for yttrium concentrations 0.65 ≤ x ≤ 0.85. This system exhibits characteristic NFL temperature dependences at low T; C/T ∼ −lnT or T−1+λ, χ ∼ 1 − cT1/2, and ρ ∼ 1 − a(T/T₀)n with 1 ≤ n ≤ 1.5. The antiferromagnetic transition temperature decreases with increasing concentration x for 0 ≤ x ≤ 0.25, while a spin glass regime persists from x = 0.25 to x = 0.65. With increasing Y concentration x, the spin glass freezing temperature is suppressed to 0 K. The onset of the NFL properties coincides with this T = 0 K phase transition, which suggests that the NFL behavior originates from a quantum critical point.; Details of both construction and implementation of a new calorimeter system are discussed. The reduced addenda for this system enables us to measure small (∼40 mg) samples. Two systems investigated with this apparatus, CeRh_1−xCo_xIn₅ and Lu_1−x Yb_xNi₂B₂C, are discussed in detail.; Specific heat measurements of the CeRh_1−xCo_xIn ₅ system reveal the occurrence of superconductivity in compounds with 0.4 ≤ x ≤ 1.0 and antiferromagnetic order in compounds with 0.2 ≤ x ≤ 0.7. Superconductivity and antiferromagnetism appear to coexist for concentrations in the range 0.4 ≤ x ≤ 0.7. The total entropy under the superconducting and antiferromagnetic transitions is constant for the samples with 0 ≤ x ≤ 0.8, indicating that the same electrons are participating in the two processes.; The interplay between superconductivity and heavy fermion behavior in the Lu_1−xYb_xNi₂B₂C system was investigated with specific heat measurements. The system shows a sharp decrease in the superconducting transition temperature and a monotonic increase in the electronic specific heat coefficient with increasing Yb concentration x. The curve of reduced specific heat jump ΔC/ΔC₀ vs T_c/T_c0, where ΔC₀ and T_c0 refer to the LuNi₂B₂C matrix, does not conform to the BCS theory, but is consistent with magnetic pair breaking theory or the theory for superconductivity in the presence of the Kondo effect for T_K/T _c0 ∼ 103, where T_K is the Kondo temperature.