Magnetic EXAFS at Gd L-edges: the spin-pir-distribution function of Gd neighbors

The purpose of the experiment is to study the normal and the Magnetic EXAFS (MEXAFS) since EXAFS is the method of choice to investigate the local pair - and spin-pair-distribution function. We present MEXAFS and EXAFS measurem ents at the L-edges of a Gd single crystal in the temperature range of 10 K to 250 K. Therefore we are able to investigate the MEXAFS in a wide range of the reduced temperature t =T/T-c of 0.04 less than or equal to t less th an or equal to 0.85 with T-c = 293 K. We find a strong decrease of the near est neighbor EXAFS which retains only about 35% of its 10 K value already a t 250 K. This highlights the importance of lattice vibrations. To analyze t he individual scattering contributions to the MEXAFS and the EXAFS, ab init io calculations (FEFF code) have been carried out. The comparison of the te mperature-dependent damping of the normal EXAFS with the spin-dependent MEX AFS allows us to separate the influence of lattice vibrations (Debye temper ature 160 K) from the magnetic ordering (Curie temperature) on the MEXAFS.