Development of the third generation synchrotron radiation sources has boosted X-ray spectroscopy, as illustrated by the discovery of a variety of new experimental techniques associated with the exploitation of the polarisation properties of X-rays. The great advantage of these techniques is their element- and orbital-selectivity originating from the optical transitions involving the core atomic state. X-ray Magnetic Circular Dichroism (XMCD) is particularly interesting since it offers a capability of quantitative determination of the orbital and spin contributions to the total magnetic moment carried by the absorbing atom. A few microns size of monochromatic x-ray beam with flexible polarization can be routinely achieved at the third generation synchrotrons and that makes spectroscopic techniques suitable for studying materials under high pressure inside diamond anvil cell (DAC). Recently we have demonstrated that the photon energy range of such experiments could be extended down to 2 keV using total fluorescence yield detection mode and a specific asymmetric DAC system using fully perforated diamond with thin plates on one side and a full diamond on the other one [1]. Exceptional performance of this set-up at low photon energies is illustrated with Phosphorus K-edge x-ray spectroscopy studies of the local electron density redistribution caused by the pressure-induced structural collapse in EuCo2P2 compound above 3.1 GPa at room temperature [2]. The same DAC system could be mounted in the main heat exchanger of an “amagnetic” cryostat and inserted in a bore of a superconducting magnet, this makes possible to perform high pressure XMCD experiments at low temperature (down to 2.7 K), high magnetic field ( up to 8 Tesla) and high pressure. Feasibility of this approach is shown with the XMCD results obtained at the Uranium M4,5- absorption edges in ferromagnetic superconductor UGe2[3].
References
[1] F. Wilhelm, G. Garbarino, J. Jacobs, H. Vitoux, R. Steinmann, F. Guillou, A. Snigirev, I. Snigireva, P. Voisin, D. Braithwaite,D. Aoki, J. P. Brison, I. Kantor, I. Lyatun, A. Rogalev, High Pressure Res. 36, 445 (2016)
[2] V. Yannello, F. Guillou, A.A. Yaroslavtsev, Z.P. Tener, F.Wilhelm, A.N. Yaresko, S.L. Molodtsov, A. Scherz, A. Rogalev, and M. Shatruk, Chem. Eur. J. 25, 5865 (2019)
[3] F. Wilhelm, J.-P. Sanchez, D. Braithwaite, J.-P. Brison, D. Aoki, A. B. Shick, and A. Rogalev, submitted to Phys.Rev.X (2019)