| AVS 60th International Symposium and Exhibition | |
| Actinides and Rare Earths Focus Topic | Monday Sessions |
| Session AC+MI+SA+TF-MoM |
| Session: | Actinides and Rare Earths: Experiment and Electron Correlation |
| Presenter: | G. Kaindl, Freie Universität Berlin, Germany |
| Correspondent: | Click to Email |
The talk addresses some aspects in the use of tunable x-rays in studies of electronic and magnetic properties of lanthanide and actinide materials by x-ray absorption fine-structure (XANES) and resonant elastic x-ray scattering (REXS), emphasizing related features of these 4f and 5f materials.
Based on early applications of L- and M-edge XANES to lanthanide valence studies, the method was applied to U and Th compounds, exploring XANES at various thresholds (L, M, N, O) [1], and then to the more radioactive actinides Np, Pu, and Am as well as to high-pressure studies. Subsequently, the method has been improved both experimentally (e.g. high-resolution XANES [2]) and theoretically [3], and even compounds of Pa, Cm, and Cf in solid and aqueous environments have been investigated by now.
Resonant magnetic x-ray scattering was first applied to Ho metal, where the magnetic scattering cross-section is enhanced by a factor of 50, when the x-ray energy is tuned across the LIII absorption edge of Ho [4]. Subsequently, much larger enhancements up to 5 magnitudes were observed at the MV edges of U in UAs [5] and of Eu in the antiferromagnetic (AFM) semiconductor EuTe [6]. In the latter, an epitaxial thin EuTe(111) film was studied, and virtually background-free magnetic Bragg-peaks with pronounced Laue oscillations were found. From these, the AFM order in the EuTe(111) film could be derived with atomic-layer resolution. The magnetization of the outermost layer was found to decrease significantly stronger with temperature than that of the bulk layer [6]. In a further pioneering experiment that employed a synchrotron slicing source for the production of tunable soft x-rays with pulse widths as short as 100 fs (probe pulses) and synchronized pump pulses of 400 nm wavelength, the dynamics of the AFM order could be studied by fs soft x-ray diffraction [7].
References
[1] G. Kalkowski, G. Kaindl, W. D. Brewer, W. Krone, Phys. Rev. B 35, 2667 (1987).
[2] J.-P. Rueff, S. Raymond, A. Yaresko, D. Braithwaite, Ph. Leininger, G. Vanko, A. Huxley, J. Rebizant, N. Sato, Phys. Rev. B 76, 085113 (2007).
[3] J. G. Tobin, K. T. Moore, B. W. Chung, M. A. Wall, A. J. Schwartz, G. van der Laan, A. I. Kutepov, Phys. Rev. B 72, 085109 (2005).
[4] D. Gibbs, D. Mills, C. Vettier, Phys. Rev. Lett. 61, 1241 (1988).
[5] S. Langridge, W. G. Stirling, G. H. Lander, J. Rebizant, Phys. Rev. B 49, 12010 (1994).
[6] E. Schierle, E. Weschke, A. Gottberg, W. Söllinger, W. Heiss, G. Springholz, G. Kaindl, Phys. Rev. Lett. 101, 267202 (2008).
[7] K. Holdack, N. Pontius, E. Schierle, T. Kachel, V. Soltwisch, R. Mitzner, T. Quast, G. Springholz, E. Weschke, Appl. Phys. Lett. 97, 062502 (2010).