Anomalous Fermi Liquid Behavior of the Dilute Uranium Alloys La_1-xU_xRu₂Si₂ (x ≤ 0.07)

Abstract

Low temperature properties of the dilute uranium alloys La_1-xU_xRu₂Si₂ (x≤ 0.07) have been investigated by means of magnetic susceptibility χ, magnetization m, specific heat C_P and electrical resistivity ρ measurements to clarify the single-U-site effects of URu₂Si₂. Local 5f electrons show a strong magnetic anisotropy along the tetragonal c axis, as is observed in other dilute alloys Th_1-xU_xRu₂Si₂ and Y_1-xU_xRu₂Si₂. As temperature is lowered below ∼60 K, the c-axis susceptibility χ_c follows a ln T function, and ρ decreases in proportion to χ_c. The 5f electronic specific heat C_P^5f/T exhibits a broad peak at ∼10 K. The entropy change associated with this anomaly below 30 K is estimated to be only about 0.3Rln 2. Although the local Fermi liquid behavior is observed in χ, C_P and ρ at very low temperatures, the ln T decrease in ρ and the small entropy change provide a remarkable contrast with those expected in the usual magnetic dilute alloys.