Magnetic and elastic properties of CeAg

Magnetic and elastic measurements in single crystals of CeAg and Ce_0.09La_0.91 Ag are presented. The magnetic susceptibility of Ce_0.09La_0.91 Ag can be quantitatively interpreted with taking Γ₈ as the ground state of the crystal field split $\text{J =}\text{5}\text{2}$ state of the Ce³⁺-ion. In CeAg we confirm a ferromagnetic phase transition at T_c = 5.3 K and a structural transition at 15 K. This latter one is clearly observed with the elastic constant measurements where c₁₁ - c₁₂ exhibits appreciable softening. This structural transition is probably due to a phonon softening at the zone boundary. The magnetic properties of CeAg, especially the small magnetic moment in the ordered region, are discussed.