M. A. Hossain, I. Zegkinoglou, Y. -D. Chuang, J. Geck, B. Bohnenbuck, A. G. Cruz Gonzalez, H. -H. Wu, C. Schussler-Langeheine, D. G. Hawthorn, J. D. Denlinger, R. Mathieu, Y. Tokura, S. Satow, H. Takagi, Y. Yoshida, Z. Hussain, B. Keimer, G. A. Sawatzky, A. Damascelli
Resonant elastic x-ray scattering (REXS) is an exquisite element-sensitive tool for the study of subtle charge, orbital, and spin superlattice orders driven by the valence electrons, which therefore escape detection in conventional x-ray diffraction (XRD). Although the power of REXS has been demonstrated by numerous studies of complex oxides performed in the soft x-ray regime, the cross section and photon wavelength of the material-specific elemental absorption edges ultimately set the limit to the smallest superlattice amplitude and periodicity one can probe. Here we show -- with simulations and REXS on Mn-substituted Sr$_3$Ru$_2$O$_7$ -- that these limitations can be overcome by performing resonant scattering experiments at the absorption edge of a suitably-chosen, dilute impurity. This establishes that -- in analogy with impurity-based methods used in electron-spin-resonance, nuclear-magnetic resonance, and M\"ossbauer spectroscopy -- randomly distributed impurities can serve as a non-invasive, but now momentum-dependent probe, greatly extending the applicability of resonant x-ray scattering techniques.
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http://arxiv.org/abs/1308.0185
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