Low Temperature Magnetic Properties of Pr(Cu,Ga)13with Orbitally Degenerate Ground State

Abstract

Magnetic susceptibility χ( T ) and the specific heat C ( T ) of a cubic compound Pr(Cu,Ga) 12.85 were measured at low temperatures down to 0.1 K. χ( T ) shows Curie–Weiss behavior down to ∼1 K and turns to saturate at lower temperatures. This behavior is best understood by assuming a Γ 5 magnetic triplet for the crystalline electric field ground state of Pr 3+ (4 f 2 , J =4). The C ( T ) data indicate a continuous releasing of the Γ 5 entropy below ∼12 K, with no evidence of a phase transition down to 0.1 K. At low temperatures below 0.5 K, a 141 Pr nuclear Schottky tail is found to develop in zero field, which can be ascribed to a hyperfine field from the Pr moment. The estimated Pr moment value (1.3 µ B ) is found to be significantly smaller than the full moment value of 2 µ B for the Γ 5 triplet, which is interpreted by fluctuating Pr moments in the ground state whose time scale is comparable to the Pr nuclear spin relaxation time. The analysis yields a large C / T value of 2.2 J/mol·K 2 at low tempera...