The temperature-induced γ-α isostructural metal-metal transition in Ce is fundamentally intriguing and provides a rare case for in-depth exploration of strongly correlated $f$-electron systems. However, the transition has yet to be well understood, with many ambiguities regarding the associated structural, electronic, and magnetic properties. In this work, we present a comprehensive study of this transition using combined state-of-the-art low-temperature x-ray diffraction and electrical and magnetic transport measurements. The reversible γ-α transition in Ce is confirmed to be coupled with a metal-to-metal crossover, which is primarily driven by the $4f$-electron instability with the involvement of intricate lattice-charge interactions. The forward $\gamma \to \alpha$ transition is found to be kinetically incomplete, and both phases coexist in a wide temperature range. An unusual ferromagnetic state is identified in γ-Ce, likely due to an indirect magnetic exchange between the localized $4f$ moments mediated by the itinerant $5d6s$ electrons (i.e., the Ruderman-Kittel-Kasuya-Yosida effect). Based on our results, the previously misassigned hexagonal “β-Ce” is excluded, and the ground state of γ-Ce is determined to be antiferromagnetic. These findings not only unravel long-standing ambiguities in Ce but also provide powerful insights into the mechanism underlying its γ-α transition.

Close

PrevNext

View figure in article

• Antiferromagnetism
• Ferromagnetism
• Phase transitions
• Structural phase transition
• Heavy-fermion systems