Abstract
Measurements of the electrical resistivity ρ as a function of temperature T, and low-temperature specific heat C as a function of T and magnetic field H, have been performed for Pr concentrations 0≤x≤1 in the system (δ≊0.05). The superconducting critical temperature (x) in the metallic phase (0≤x≲≊0.5) was determined from the resistivity ρ(x,T), while the Néel temperature (x) in the insulating phase (≲x≤1) was inferred from specific-heat anomalies due to antiferromagnetic (AFM) ordering of the Pr ions. The effect of ‘‘chemical’’ pressure on (x) in the system is opposite to that of applied hydrostatic pressure. The Pr contributions to the specific heat in the insulating phase have the form C(T)= for T<, characteristic of three-dimensional AFM magnons. In contrast, the Pr contribution to C(T) in the metallic phase takes the form of a broad anomaly that can be described by a spin-1/2 Kondo model. The entropy associated with the Pr specific-heat anomalies in both the metallic and insulating phases is close to R ln2, indicative of a doublet ground state for Pr in the crystalline electric field and a Pr valence close to 4+.
- Received 17 May 1991
DOI:https://doi.org/10.1103/PhysRevB.44.6999
©1991 American Physical Society