X-Ray Absorption Spectroscopy of 4f Compounds and Future Directions Toward Time-resolved Measurements

Abstract

4f electron compounds like Yb systems are often called heavy electron systems, and show various anomalous quantum properties such as Kondo effects and superconductivity. However, compared to more common d electron systems, little has been studied about photoinduced phase transitions in f electron compounds. Here, we first describe the construction of soft X-ray time-resolved measurement instruments. We recently succeeded in time-resolved X-ray magnetic circular dichroism (XMCD) measurements in soft X-ray beamline BL07LSU in SPring-8. By using Fe L edge (soft X-ray), we observed demagnetization dynamics of FePt thin films with perpendicular magnetic anisotropy. As for dynamics study of Yb systems, we used both soft X-ray time-resolved and hard X-ray Yb L₃ edge absorption measurements. Here, we describe our static temperature-dependent measurements in SPring-8 and our challenges for time-resolved measurements in SACLA. We would like to continue systematic studies of 4f electron dynamics.