H. B. Rose

Magnetic linear dichroism in soft X-ray core level photoemission from iron

Abstract We have observed magnetic linear dichroism in soft x-ray core-level photo-emission from ferromagnets: With linearly polarized light, the Fe 3p lineshape depends strongly on the relative orientation of the light electric field vector E and the magnetization vector M . For s-polarized light and collinear orientation of E and M the core level line shows a single peak. With E ⊥ M a double-peaked line is observed. We attribute this change to the MLD effect as predicted recently 1 .

High-efficiency spin polarimetry by very-low-energy electron scattering from Fe(100) for spin-resolved photoemission

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.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.

Linear magnetic dichroism in photoemission

Results for the linear magnetic dichroism of Fe 2p spin-resolved photoemission with high energy resolution are reported. The results are qualitatively similar to those for the 3p level, with the advantage that the fine structure split sublevels (j = 1/2 and j = 3/2) are well separated, facilitating comparison with theoretical models. The finite dichroism in the energy region between the two photoemission peaks is not caused by secondaries, but appears to be a nontrivial effect. The 3p dichroism depends on photon energy: it is maximum at 140 eV, and vanishes around 300 eV photon energy.

Magnetic linear dichroism in angle-resolved valence band photoemission from Fe(001)

Abstract We report the observation of magnetic linear dichroism in angle resolved valence band photoemission from Fe(001), manifesting itself in a change of the spectrum upon reversal of the magnetization direction.

A new magnetic linear dichroism in photoabsorption at the Fe M2,3 edge

Abstract We have found a new type of magnetic linear dichroism in photoabsorption spectra at the Fe M 2,3 edge. The spectra excited by p-polarized light at oblique incidence show dichroism when the magnetization direction changes from parallel to antiparallel to n × q , where n is a vector perpendicular to the sample surface and q is the photon momentum. The dichroism is enhanced when the light impinges on the sample towards grazing incidence.

A new type of magnetic linear dichroism at Fe and Co M2,3 edges

We have found a new type of magnetic linear dichroism in photoyield spectra at the Fe and Co M2,3 edges. Spectra excited by p-polarized light at oblique incidence show cross section dependence on the sign of the magnetization. The experimental geometry is the same as that of the transverse magneto-optic Kerr effect (T-MOKE). The dichroism is enhanced when the light impinges on the sample towards grazing incidence. The T-MOKE at the Co M edge also measured simultaneously. The new type of dichroism can be applied for imaging of magnetic domains of surfaces by a photoelectron microscopy.

INFLUENCE OF PHOTOELECTRON DIFFRACTION ON MAGNETIC LINEAR DICHROISM

We studied the influence of photoelectron diffraction on magnetic linear dichroism and spin polarization in Co and Fe 3p photoemission excited by linearly polarized synchrotron radiation. We find a strong variation of the magnetic linear dichroism with emission direction. The spin polarization related to the spin–orbit interaction varies in a similar manner. This angular variation closely tracks that of the magnetic dichroism. In contrast, the exchange-induced spin polarization (-12+2)% does not vary appreciably with emission angle. These findings suggest that the main cause for the observed effects is the angular momentum character of the photoelectron wave.

Element-specific magnetic domain imaging based on linear and circular magnetic dichroism in photoabsorption

The discovery of magnetic dichroism in core level spectroscopy opened the route to magnetic domain imaging. By employing light in the soft X-ray regime one obtains chemically specific information. Besides the commonly used circular magnetic dichroism (MCD), we demonstrate feasibility of using linear magnetic dichroism in absorption for domain imaging in the photo electron emission microscope (PEEM). By combining different light polarizations, one obtains vectorial information on the magnetic moment distribution close to the surrface.

Angular dependence of the magnetic linear dichroism in Fe 3p photoemission

We investigate the angular dependence of the magnetic linear dichroism in the angular distribution (MLDAD). An atomic description predicts a sin(2θ) dependence. We find deviations from this behaviour, which can only partly be explained by photoelectron diffraction.

Magnetic linear dichroism in spin-resolved Gd 4f photoemission

Abstract Gd 4f photoemission excited by linearly polarized radiation is shown to exhibit a magnetic dichroism, similar to that reported earlier for Fe 3p and 2p photoemission. The dichroism can be observed if electric radiation field, sample magnetization, and electron emission form a chiral system. The results show similarities to data obtained with circularly polarized radiation. Spin-resolved studies show that the exchange-related spin polarization has a constant sign throughout the Gd 4f spectrum, while the spin-orbit-related polarization switches its sign.