SPIN FLIP IN RESONANT PHOTOEMISSION FROM GD

We report the observation and theoretical analysis of magnetic circular dichroism of low-spin Gd $4f$ photoemission (PE) lines in the Gd ${M}_{5}$ photoexcitation region. With circularly polarized x rays tuned to previously unresolved absorption lines of magnetized Gd metal, low-spin and high-spin $4f$ PE lines become nearly equally strong. The observations are in excellent agreement with a state-of-the-art atomic multiplet calculation proving that spin-flip processes in resonant PE from lanthanides occur predominantly during the photoexcitation step.