Magnetic and Thermal Properties of Cubic Single-Crystal PrCu4Ag

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We succeeded in synthesizing a new cubic intermetallic compound PrCu4Ag in a fcc structure. Measurements of X-ray diffraction, magnetic susceptibility, magnetization, specific heat, electrical resistivity, thermal expansion, and elastic constants have been performed on single crystals of PrCu4Ag. A maximum value of $\chi(T)$ with a corresponding peak in $C(T)$ suggests that an antiferromagnetic phase transition occurs at $T_{\text{N}} = 2.4$ K, where a sudden decrease in $\rho_{4f}(T)$ and a sharp peak in the thermal expansion coefficient $\alpha(T)$ were observed. Characteristic Curie-type softening was observed in the temperature dependence of the transverse mode for $(C_{11} - C_{12})/2$ and $C_{44}$ from 70 K down to $T_{\text{N}}$, which implies that the crystalline electric field (CEF) ground state is the magnetic triplet $\Gamma_{5}$. The anisotropic properties in $M(T,H)$ and $C(T,H)$ are studied when the external magnetic field is applied in the $\langle 100\rangle$, $\langle 110\rangle$, and $\langle 111\rangle$ directions. Another anomaly observed at approximately 10 K in $\chi(T)$ is considered to be related to possible disorder behavior. The low-$T$ behavior and the possibility of quadrupole fluctuation are discussed with respect to the CEF effect. All the experimental results in the present study are summarized in a magnetic phase diagram.
2010-11-15