X-ray magnetic circular dichroism study of uranium/iron multilayers

Abstract

X-ray magnetic circular dichroism ͑XMCD͒ measurements were performed at the U M 4,5 edges and Fe K edge on well-defined uranium/iron multilayers with different compositions. The multilayers have layer thicknesses in the range 9 -40 Å for uranium and 9 -34 Å for iron. At both 10 K and room temperature, the U layers are magnetically polarized in all of the multilayers studied. To deduce the magnetic moment on the uranium from the XMCD results requires assumptions about the magnetic dipole operator ͗T Z ͘ in the analysis, and this is discussed in detail. Given the most likely scenario of strong hybridization between the U 5f and Fe 3d states, the largest value of the induced U moment is ϳ0.12 B , which is located primarily at the interface and oscillates within the uranium layer.

Profile of the U5fmagnetization inU∕Femultilayers

“…3, determined from the fitted calculations of the charge scattering, are similar in shape and magnitude to those measured across the U M 4 edge in other uranium systems 24 . The good agreement between the fluorescence measurements, corrected for self absorption effects 12 , and the imaginary part of the resonant scattering factor, shown in Fig. 3 (b), may be attributed to the large number of energies sampled.…”

“…A moment of about 1µ B was predicted, but was found to be considerably smaller (∼ 0.1µ B )in XMCD studies 12 . This can be attributed to differences between the idealized model calculation and the real multilayers.…”

“…The insert of Fig. 3 (b) shows a comparison of the self-absorption corrected fluorescence data 12 with the imaginary part of the resonant scattering factor. The magnetic-charge interference scattering, (I + − I − ), was calculated separately for each sample.…”

“…At these energies, it is most often the L edges of the rare-earth elements which are of interest 9 , but some progress has been made in understanding the induced moment in 5d transition metal systems also 10 . Preliminary measurements at the U M 4 edge have reported an induced magnetic moment on the U site 11 and later, the separation of spin and orbital components of this moment, using x-ray magnetic circular dichroism (XMCD) 12 . The total magnetic moments in this case are small (∼ 0.1µ B ).…”

Resonant elastic X-ray scattering from 5f systems

“…There is no magnetism in uranium, but REXS may be able to help with understanding the interfacial features -up to now efforts have been concentrated on resonant reflectivity and understanding how the induced moments (by hybridisation with neighbouring Fe layers) are distributed within the U layers of the multilayers [29]. In this respect XMCD measurements, another element-specific technique, are also very valuable [30].…”