We describe concept, design, and performance of a novel spin polarimeter based on spin-dependent specular reflection of electrons from a Fe(100) surface. The Fe surface is prepared as an ultrathin film on Ag(100). By tuning the energy of the electrons to a critical point in the Fe band structure, a large spin asymmetry combined with a large scattering efficiency is achieved. The polarimeter yields a figure of merit up to 10−2 for the best Fe(100) surfaces.

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We report a dependence of the photoabsorption cross section as measured by total electron yield at the Fe and Co 3p thresholds on the sign of the magnetization for p-polarized light at oblique incidence.Peak-to-peak asymmetries up to 4% are observed. The asymmetry increases towards grazing incidence, where the total sample current is smallest.The transverse magneto-optic Kerr effect measured simultaneously shows a peak-to-peak asymmetry of up to 23% at the Co 3p threshold. The dichroism is used to image magnetic domains on an Fe (100) surface in a photoelectron emission microscope. PACS numbers: 78.20.Ls, 75.60.Ch, 78.70.Dm Spectroscopy of the core levels of the ferromagnetic transition elements has shown in recent years to be surprisingly rich in features caused by the Coulomb and exchange interactions between the core hole and the spinpolarized valence electrons. X-ray absorption experiments (XAS) with linearly polarized light [1] show a change of the spectra when the polarization vector is either parallel or perpendicular to the magnetization axis, according to the selection rules Am = 0 or Am =~1 , respectively. Magnetic circular dichroism (MCD) in x-ray absorption [2,3]can be understood as a spin-dependent excitation of core electrons into empty states above the Fermi level, whichbecause of the ferromagnetism are spin polarized [4].The spin dependence in the excitation arises from coupling between light helicity and the orbital momentum of the excited electron, which is in turn coupled to the spin of the photoexcited electron by spin-orbit interaction. Sum rules, which allow one to extract quantitatively spin and orbital moments, make MCD in absorption a very attractive technique [5]. By measuring the photoabsorption cross section via the total photoelectron yield of the sample, it is even possible to obtain spatially resolved and chemically specific magnetic information [6].In photoemission, even though the final state of the photoelectron far above the Fermi level has only negligible exchange and spin-orbit interactions, related effects can also be observed. It is well known that core level photoelectrons from ferromagnets in general carry a spin polarization due to exchange [7]. Apart from magnetic circular and "conventional" (as described above for XAS) linear dichroisrn, a new type of magnetic linear dichroism was recently reported for photoemission appearing on magnetization reversal [8]. This effect requires that the vectors of magnetization, electric radiation field, and electron emission form a chiral system with the angle between light polarization and electron emission different from 90, and occurs only in angle-resolved experiments. In photoabsorption, the angular acceptance of the excited electrons is not restricted, so that it is, in principle, an angle-integrating experiment. However, Kao and co-workers [9] reported in 1990 for photon energies near the Fe 2p excitation thresholds a change of the refIectivity for obliquely incident p-polarized light when the magnetization is switched between th...

Linear magnetic dichroism is studied for the Fe 2 p level by angle-and spin-resolved photoemission with high energy resolution. The dichroism occurs in angle-resolved experiments for a geometry as in the transverse magneto-optic Kerr effect, i.e., on reversal of sample magnetization in the direction normal to the plane defined by light polarization and electron emission. The large spin-orbit splitting allows us to investigate the jϭ1/2 and jϭ3/2 states separately. Spin analysis allows differentiation between polarization effects related to exchange and spin-orbit interactions. The results are discussed in the framework of an atomic model, where the exchange interaction between the magnetic d shell and the core hole lifts the degeneracy of magnetic sublevels of the core hole spectrum. The model is able to explain the general trend in the spectra, but does not fully account for the observed shapes of the jϭ3/2 peaks. The analysis shows that the dichroism is governed by the spin polarization parameter which determines the spin-orbit-induced spin polarization. This shows that if there is a magnetic dichroism then there is a finite spin-orbit-induced spin polarization. The rich structures observed in our complete experiment are evidence for the influence of many-electron effects in the Fe 2p spectrum.

We have observed a new type of magnetic linear dichroism in angle-resolved, spin-integrated photoemission: For p-polarized light under oblique incidence the Fe 3p core level peak position and line shape change when the sample magnetization is reversed. Spin-resolved measurements show that the effect is due to spin-orbit interaction in the presence of exchange interaction. The effect can be used for chemically specific diagnostics of magnetic structures.