* Corresponding author. Fax: #33-4-76-88-2743. E-mail address: tjernb@esrf.fr (O. Tjernberg) Physica B 281&282 (2000) 723}724 Resonant spin resolved photoemission on Ce O. Tjernberg*, M. Finazzi,L. Duo` , G. Ghiringhelli, P. Ohresser, N.B. Brookes European Synchrotron Radiation Facility, BP 220, F-38043 Grenoble Cedex, France TASC-INFM, Elettra Synchrotron Light Source, 34012 Basovizza, Trieste, Italy INFM-Dipartimento di Fisica, Politecnico di Milano, I-20133 Milan, Italy Abstract Spin resolved resonant photoemission using circularly polarized light has been performed on thick -Ce "lms and the measured photoelectrons show a high degree of polarization in agreement with a simple model calculation. The two near Fermi edge features are shown to in#uence the polarization spectrum in opposite directions, as intuitively expected for states with opposite spin}orbit alignment.  2000 Elsevier Science B.V. All rights reserved. Keywords: Ce; 4f-photoemission; Spin polarization The proper description of the electronic structure of Ce and Ce compounds has been a subject of intense interest and debate for many years (see Refs. [1,2]). The interac- tion between the Ce 4f states and the other conduction states are often described in the single impurity Anderson model (SIAM) where the 4f level is treated as an impurity in the matrix of the other conduction states. Photoemis- sion spectroscopy has played an important role in un- raveling of the electronic structure of these compounds; however, since it is not possible to carry out conventional spin resolved photoemission on Ce (-Ce is paramag- netic), the spin nature of the features observed in normal and resonant photoemission has not been experimentally veri"ed. The new technique of resonant spin resolved photoemission with circularly polarized light is, however, applicable to all compounds where normal resonant photoemission can be applied, independent of the mag- netic properties [3]. In this report, a few results from a spin resolved resonant photoemission study of -Ce are presented and the spin nature of the valence band states is discussed. The measurements were performed at beamline ID12B of the European Synchrotron Radiation Facility (ESRF) in Grenoble, France. A hemispherical analyzer with a &mini-Mott' spin detector [4] was used to collect the photoelectrons over a $203 acceptance angle. The photon energy resolution used was 300 meV and the detector resolution 150 meV giving a combined resolu- tion of 335 meV. The -Ce samples used were thick polycrystalline "lms deposited on a stainless-steel sub- strate by electron-beam evaporation from a high-purity (99.99%) Ce target. During the experiment, the base pressure in the measurement chamber was &310 mbar and new Ce was deposited approximately every 6 h. The measurements were performed at room temper- ature. In Fig. 1, a typical X-ray absorption spectrum (XAS) of such a "lm is shown. The multiplet structure of the Ce M  edge is partly resolved and the shape of the spec- trum is in agreement with previously published XAS spectra for -Ce. The weak satellite features that are visible &5 eV above the main peaks are usually at- tributed to a 4f "nal state. A weak satellite intensity can therefore be interpreted as a high n  count and thus a low hybridization. Indicated in Fig. 1, is also the photon energy at which the spin resolved resonant photoemis- sion spectrum was recorded. At this energy, the absorp- tion "nal state (resonant photoemission intermediate state) is dominantly of (3d  ,I ) J"  character [5]. This point is important for the modeling of the resonance process as discussed below. 0921-4526/00/$ - see front matter  2000 Elsevier Science B.V. All rights reserved. PII: S 0 9 2 1 - 4 5 2 6 ( 9 9 ) 0 1 0 1 9 - 4