Journal of Electron Spectroscopy and Related Phenomena 110–111 (2000) 287–304 www.elsevier.nl / locate / elspec Magnetic circular dichroism in soft X-ray emission of itinerant and localized magnets * L.-C. Duda Department of Physics, Uppsala University, Box 530, S-75121 Uppsala, Sweden Abstract I present spin-resolved valence band studies of magnetic 3d-transition metal materials using magnetic circular dichroism in soft X-ray emission (SXEMCD). The non-resonantly excited SXEMCD of Fe, Co, and Ni, as well as several compounds with ferromagnetically aligned Mn atoms are compared. A simple model picture accounts for the basic principles involved. Quantitative estimates show that it is likely that substantial valence-band relaxation due to the intermediate-state core hole takes place in itinerant systems. A z 1 1 approximation shows that the magnitude of SXEMCD is proportional to the magnetic moment of such a core hole impurity. Magnetic circular dichroism in resonant inelastic X-ray scattering (RIXS) is discussed. For strongly localized 3d-electrons as found in some Mn compounds RIXS probes dd-excitations and the corresponding MCD. For more itinerant systems, such as iron, it is argued that RIXS leads to the observation of a convolution of the occupied and (parts of) the unoccupied 3d-bands. Finally, an overview of possible future developments in helicity-resolved SXES is given.  2000 Elsevier Science B.V. All rights reserved. Keywords: X-ray emission; Magnetism; Circular dichroism; Transition metals; dd-excitations 1. Introduction been known for a long time to be strongly related with the occupied partial density of states (PDOS). Magnetic dichroism in soft X-ray spectroscopies MCD in SXES (or short: SXEMCD), predicted by has been a topic of intense study for the last decade. Strange et al. [2] who used the term ‘dichroic Especially magnetic circular dichroism (MCD) in fluorescence’, is the spin-resolved version of the (soft) X-ray absorption (XA), predicted by Thole et SXES, in analogy to spin-resolved electron spec- al. [1] in 1985, has matured to a standard technique troscopy for Auger and photoelectron spectroscopy. used to probe site- and element-specific magnetic All these later techniques probe spin-dependent moments. MCD in soft X-ray emission spectroscopy valence band states and are highly surface sensitive. (SXES) is an instrumentally much more demanding On the other hand, SXES is a highly selective spectroscopic technique and has developed sub- spectroscopy which combines probing depth (pure sequently. The information contained in the spectra photon spectroscopy), local information (core level 1 of ‘ordinary’ soft X-ray emission (fluorescence) has spectroscopy), and symmetry selectivity (dipole selection rules). Since SXES does not involve the *Tel.: 146-18-18-351; fax: 146-18-18-3524. detection of electrons it is possible to apply strong E-mail address: laurent@fysik.uu.se (L.-C. Duda). 1 electrostatic or magnetic fields during measurement. This term is introduced as a means of distinguishing X-ray The final state of continuum excited SXES — a hole fluorescence from resonant X-ray scattering which may give a large contribution in a spectrum. See Section 3.2. in the valence band — is similar to that of X-ray 0368-2048 / 00 / $ – see front matter  2000 Elsevier Science B.V. All rights reserved. PII: S0368-2048(00)00169-9