Resonant magnetic x-ray scattering in the antiferromagnet Ce(Fe1-xCox)2
Résumé
Magnetic resonant x-ray scattering experiments have been performed in Co-doped CeFe2 at Ce L2,3 and Fe K edges in the antiferromagnetic state. We could confirm a previous result that Ce moments lie parallel to the distortion rhombohedral axis ⟨111⟩ and Fe magnetic moments are arranged in a noncollinear structure by combining experimental data and numerical ab initio calculations at the Fe K edge. Interestingly, we were also able to qualitatively reproduce the main three peaks in the energy scan at Ce L edges by means of single-particle relativistic multiple-scattering calculations, provided that we extend the cluster radius up to the third shell of Ce nearest neighbors. We not only proved the main dipolar character of these resonances but also identified a non-negligible quadrupolar contribution. These results have suggested analyzing the orbital character of each peak through an azimuth scan. Experimentally, only the lower-energy peak showed the azimuth modulation expected for a quadrupolar transition. These findings, pointing to a single energy-position of 4f states, have a natural theoretical framework in a "monovalence" model, instead of the usually adopted "mixed-valence" model. Further analysis in the future would be desirable to clarify this fundamental issue. Finally, the magnetic phase diagram under applied magnetic field is also reported and compared to previous neutron scattering data.