Surface and image-potential states of gadolinium investigated with spin- and time-resolved 2PPE

It is still an open question which microscopic processes are responsible for the laser-induced ultrafast demagnetization in ferromagnetic materials. Most of the experiments performed so far lack spin-resolution. Our first goal is to investigate the occupied majority and unoccupied minority 5dz2 surface state (SS) of Gd. We investigate exchange splitting ΔEex, binding energy and spin polaristion of the SS and their dependence on the temperature. Here the fundamental of our Ti:Sa laser serves as IR pump and the frequency tripled UV as probe pulse (photon energies 1.5 and 4.5 eV, respectively, pulse durations ∼0 fs). In a second step we will focus on the image-potential states which are also expected to show ΔEex and spin dependent lifetimes (frequency doubled photons at hν=3 eV will serve as pump and 1.5-eV-photons as probe). As samples we use 100-A-thick Gd(0001) films grown in situ on W(110).