Intrinsic coercivity induced by valence fluctuations in Ce(Co1-xCux)5 permanent magnet

In rare-earth permanent magnets, magnetization and Curie temperature are mainly dominated by 3d-electrons of Fe-group elements, and magnetic anisotropy arises from 4f-electrons, typically as an outcome from the combination of the crystal field effect and the spin-orbit interaction (SOI). Here we propose enhancement of an intrinsic coercivity due to the valence fluctuation derived from the 4f-electrons in Ce-based rare-earth magnets. Valence-fluctuations combined with SOI bring an effective magnetic anisotropy driven by kinetic energy in the hybridization of delocalized 4f-electrons and conduction electrons. This kinetic-energy-driven anisotropy has an order of magnitude stronger energy scale than the magnetic anisotropy driven by potential energy of well localized 4f-electrons in the crystal fields. The relatively strong coupling between 4f-3d electrons make such kinetic-energy driven anisotropy robust against high temperatures. This mechanism of intrinsic magnetic anisotropy is not only scientifically intriguing but also promising for application to permanent magnets.
International Conference on Strongly Correlated Electron Systems (SCES 2020/21)