Magnetic Properties of Epitaxially Grown Films

With increasing film thickness the electronic structure of the adsorbate overlayer becomes undistinguishable to that of the bulk material this will be demonstrated for Fe evaporated on W(llO) [13]. In the following it will be shown that a thickness of 20 layers is already sufficient to map the transitions in the spin resolved bulk band structure of Fe(llO). The analogous behavior was found for Co(OOOl) films on W(llO) [14]. 

In the upper part of Fig. 5.5 photoelectron spectra of a 7 ML thick iron film on W(llO) taken with left and right circularly polarized light are displayed for opposite magnetization direction (M and M ). The required geometric arrangement was presented in Fig. 2.2. The data clearly show a huge intensity difference in the main iron Jid band directly at the Fermi level [26], the corresponding asymmetry A  

The results presented above were obtained in normal emission. Now, the effect of changing the parallel component of the electron momentum vector, i.e. dispersion, will be discussed. 

In the following it will be demonstrated that magnetic dichroitic effects not necessarily need linearly or circularly polarized light but can already be observed with unpolarized light (being named UMDAD). 

In this experiment [42], the photoelectrons are detected in the direction of the surface normal. The beam of unpolarized light forms an angle 0ph with the surface normal. The direction of the sample magnetization M is perpendicular to both the surface normal and the photon beam. It follows from theory [32] that for this geometry and for the absorption of linearly polarized light with polarization perpendicular to M, MLDAD is defined by the equation  

---