MCD Observed by Photoemission on the 2P Lines of Iron Films Under an External Applied Field
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MCD OBSERVED BY PHOTOEMISSION ON THE 2p LINES OF IRON FILMS UNDER AN EXTERNAL APPLIED FIELD.
C. Boeglin*, E. Beaurepaire*, B. Carri~re*, K. Hricovini** and G. Krill**. *IPCMS-CNRS, Universitý Louis Pasteur, F-67070 Strasbourg, France. **LURELP CNRS, Universitý de Paris-Sud, F- 91405 Orsay, France.
ABSTRACT Circular Dichroic X-ray Photoemission Spectroscopy (CDXPS) experiments have been performed on the 2p core level spectra of polycrystalline Fe film which was magnetized by a low excitation field. The ability to perform the CDXPS experiments in a non remanent mode at a photon energy of 2100 eV opens new and interesting possibilities for the MCD technique in the study of surface and interface magnetism. Our work on this polycrystalline iron gives some new insights into the understanding of the MCD mechanism. First results show a similar angular variation for the measured asymmetry, as those observed on a Fe bcc (100) single crystal remanently magnetized in the [100] direction. Our results make clear that the parameters governing the behaviour of the asymmetry factor (A) are not completely described by the relative direction of the magnetization (M) with the polarization vector of the incident beam (q) and the direction of detection of the photoelectrons (z). The specific outcoming of this work is to clearly show that this behaviour of A is not connected to the crystalline structure of the film for our
geometries. INTRODUCTION. Magnetic circular dichroism (MCD) is now widely used to study the local magnetic properties of atoms in any magnetic materials. If the absorption experiments are now rather
well described for localized and itinerant magnetic systems [1 - 61, the MCD effect observed by photoemission is to first order explained by a simple extended "absorption model" [31 where the emission direction is not explicited. Recently new experiments showed interesting results on a Fe(1 10) single crystal face since a magnetic asymmetry was observed on the Fe2p levels in a "forbidden geometry" considering absorption measurements [7]. On the contrary to absorption experiments, where the electrons produced by the absorption process are not analysed, photoemission experiments involve the detection of photoelectrons with a well-defined direction with
respect to the magnetization M, the surface normal and the wave vector q of the photon. Thus, the asymmetry factor A=[I(-M)-I(+M)]/[I(-M)+I(+M)] can be shown to be strongly dependent on the detection angle [7,8,12]. Recently, a CDXPS experiment has been performed on the Ni 3p core level from a Ni(110) surface [9]: the importance of the orbital magnetic moment on the surface layer has been
invoked in order to explain the large discrepancy concerning the magnitude of the asymmetry, within the above mentioned model. Analytical calculations [13] has shown that the asymmetry A is dependent on both, the rate
of the circularly polarized light and the rate of the linearly polarized light.
Mat. Res. Soc. Symp. Proc. Vol. 313. c 1993 Materials Research Society
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