XMCD under pressure at the Fe K edge on the energy‐dispersive beamline of the ESRF

The present paper demonstrates the feasibility of X‐ray absorption spectroscopy (XAS) and X‐ray magnetic circular dichroism (XMCD) at high pressure at the Fe K edge on the ID24 energy‐dispersive beamline of the ESRF. In 3 d transition metals, performing experiments at the hard X‐ray K edge rather than at the magnetically interesting soft X‐ray L edges represents the only way to access the high‐pressure regime obtainable with diamond anvil cells. The simultaneous availability of a local structure (XAS) and of a magnetic (XMCD) probe on the sample under identical thermodynamical conditions is essential for studying correlations between local structural and magnetic properties. The state‐of‐the‐art theoretical understanding of K ‐edge XMCD data is briefly summarized, and the set‐up of beamline ID24 for high‐pressure XMCD experiments is illustrated and the conditions required to perform measurements at the K edges of 3 d transition metals are underlined. Finally, two examples of recent high‐pressure results at the Fe K edge in pure Fe and Fe 3 O 4 powder are presented.