Evidence for localized 4<i>f</i>states in α-Ce

Abstract

Paramagnetic spectra of \ensuremath{\gamma} and \ensuremath{\alpha}-Ce measured at the same temperature using high-energy neutrons (\ensuremath{\sim}2 eV) yield a 4f occupancy of \ensuremath{\sim}0.8 in \ensuremath{\alpha}-Ce. This phase of Ce also shows single-ion magnetic response but with a high Kondo energy of \ensuremath{\sim}1800 K. In \ensuremath{\gamma}-Ce we observe the $^{2}$${\mathit{F}}_{5/2}$${\ensuremath{\rightarrow}}^{2}$${\mathit{F}}_{7/2}$ spin-orbit (SO) excitation at \ensuremath{\sim}260 meV. Remarkably, \ensuremath{\alpha}-Ce also reveals a broad SO excitation shifted to a higher energy (\ensuremath{\sim}450 meV). These observations reinforce the idea of localized 4f states in \ensuremath{\alpha}-Ce and k-f hybridization as the driving mechanism for the \ensuremath{\gamma}\ensuremath{\leftrightarrows}\ensuremath{\alpha} transition.