4fSpin Dynamics of Isolated Nd, Pr, and Ce Ions in Simple Metals

The $4f$ spin dynamics of extremely dilute Nd, Pr, and Ce ions in liquid metals are microscopically observed by the time-differential perturbed $\gamma$-ray distribution method. The $4f$ spin rates are dominated by strong mixing exchange interaction in all systems investigated, which is, e.g., reflected by a Kondo-like behavior for Nd systems. The pressure-driven valence transition in dilute $\mathrm{La}\mathrm{Pr}$ alloys is probably of the $4f^2\to 4f^1$ type. One has to expect that $4f$ instabilities might occur for all light rare-earth ions in appropriate systems.