Temperature-dependent magnetic EXAFS investigation of Gd

Abstract

Magnetic EXAFS (MEXAFS) is the helicity-dependent counterpart of the well-established EXAFS technique. By means of MEXAFS it is possible not only to analyze the local magnetic structure but also to learn about magnetic fluctuations. Here we present the MEXAFS of a Gd single crystal at the L 3,2-edges in the temperature range of 10–250 K. For the first time MEXAFS was probed over a large range in reduced temperature of 0.04⩽ T/ T C⩽0.85 with T C=293 K. We show that the vibrational damping described by means of a Debye temperature of θ D=160 K must be taken into account for the spin-dependent MEXAFS before analyzing magnetic fluctuations. For a detailed analysis of the MEXAFS and the EXAFS, the experimental data are compared to ab initio calculations. This enables us to separate the individual single- from the multiple-scattering contributions. The MEXAFS data have been recorded at the ID 12A beamline of the European Synchrotron Radiation Facility (ESRF). To ensure that the degree of circular polarization is kept constant, the undulator gap was scanned so that the maximum photon flux at every energy point was used.