Orbital and spin sum rules in x-ray magnetic circular dichroism

Abstract

X-ray magnetic circular dichroism (XMCD) in the L & 3 absorption spectra of transition metals is a relatively new experimental technique for the investigation of magnetism. XMCD is element specific, giving it obvious advantages over methods which measure averaged magnetic properties. Another potential strength of XMCD is the separate quantitative measurement of (Lz ) and (Sz ) through application of dichroism sum rules. In this paper we present the results from a set of experiments designed to test the applicability of the dichroism sum rules to XMCD spectra measured by total electron yield. We find that with proper experimental control of angle of incidence, degree of polarization and film thickness, the total electron yield measurement of absorption spectra is accurate to within 5%. The uncertainties involved in applying the dichroism sum rules are discussed in detail, including possible effects of diffuse magnetic moments which are known to exist in Fe, Co, and Ni. The magnitude of these uncertainties makes it difficult to obtain absolute values of (Lz ) and (Sz ), however, the dichroism sum rules are shown to be qualitatively accurate and therefore capable of measuring changes in (Lz ) and (Sz ).

Quantitative experimental determination of site-specific magnetic structures by transmitted electrons

“…The site-specific MCD spectra were extracted by least square fitting method from a series of EMCD spectra with the minimal residual errors for different dynamical diffraction conditions. Based on sum rules for MCD spectra, magnetic values are calculated for each atom in NFO 26,27 . Calculations of the magnetic structure of NFO were carried out using the projector augmented-wave method 36 within the density functional theory, as implemented in the VASP code 37 .…”

“…Using the sum rules 4,11,26,27 , which allow a quantitative assessment of spin and orbital magnetic moments from the site-specific MCD spectra (Supplementary Methods), we further calculate the site-specific magnetic moments as shown in Table 1. Compared with the results obtained by XMCD, neutron diffraction and first-principle calculation 20,[28][29][30] , site-specific EMCD method shows the unique capability of solving magnetic structures experimentally and simultaneously achieving very comprehensive magnetic information.…”

Origin of the interlayer exchange coupling in[Co∕Pt]∕NiO∕[Co∕Baruth1, Keavney2, Burton3 et al. 2006Phys. Rev. B

“…23, the oxidation of Co was limited to about 2 Å at the Co/ NiO interface. In order to calculate the fraction of the Co signal that arises from this thin layer at the interface, we follow the procedure outlined by O'Brien and Tonner, 24 where the contribution from a single Co layer of thickness dz is…”

Electron sampling depth and saturation effects in perovskite films investigated by soft x-ray absorption spectroscopy

“…To obtain reliable quantitative results from the observed electron yield signal, investigation of the extent of the saturation effect in the absorption process is essential [6,7,11,18,19,20,21,22,23]. In TEY, saturation arises when the electron sampling depth d becomes comparable to the photon penetration depth λsinθ, i.e.…”