Local Electronic and Magnetic Structure of Ni below and aboveTC: A Spin-Resolved Circularly Polarized Resonant Photoemission Study

We report the measurement of the local Ni $3d$ spin polarization, not only below but also above the Curie temperature $\left(T_C\right)$, using the newly developed spin-resolved circularly polarized $2p\left(L_3\right)$ resonant photoemission technique. The experiment identifies the presence of ${3d}^8$ singlets at high energies and ${3d}^8$ triplets at low energies extending all the way to the Fermi energy, both below and above $T_C$, showing that it is the orbital degeneracy of the $3d$ band and the Hund's rule splitting which is of utmost importance to understand Ni and other $3d$ ferromagnets.