Polarized XAFS study of Mg K-edge for MgB2 on ZnO

Abstract

Polarization-dependent Mg K-edge XAFS study was carried out for MgB 2 films epitaxially deposited by MBE method on ZnO single crystal.

Local Structure Analysis of MgB₂ Thin Films by Polarized XAFS

“…The dampling factor S 2 0 is determined from 50 nm film results. The local structure of 50 nm MgB 2 film is almost same as crystal one [3]. On the other hand the interatomic distances (r) for 30 nm film are slightly shorter than that for 50 nm film.…”

“…There is a clear difference between thinner (10 and 20 nm) MgB 2 films and thicker (30 and 50 nm) films. The structure of 50 nm MgB 2 film is almost same as 150 nm film and shows hexagonal structure [3]. The result suggests that the local structure of the 10 nm and 20 nm thick sample was disturbed from the MgB 2 crystal.…”

“…We have previously analyzed the local structure of 50 nm and 150 nm MgB 2 thin films and obtained result that they show almost same structure as MgB 2 hexagonal crystal and their structural change was significant [3]. For application of the superconducting films to the industry, to study the structure for thinner films is important.…”

Enhancement in High-Field Jc Properties and the Flux Pinning Mechanism of ZnO-Buffered MgB2 Films

“…Local structure studies using Raman spectra and EXAFS measurements have revealed the presence of local lattice distortion in MgB 2 films owing to the application of a ZnO buffer layer. , While the Mg–Mg bond ordering showed insignificant fluctuation, the Mg–B bond ordering was found to be heavily affected by the ZnO thickness . To find a correlation between the local structure distortion and the second pinning mechanism, renormalization of the Fourier transform of the Mg–B bond ordering with respect to the Mg–Mg bond ordering was measured by Mg K-edge EXAFS, for which the results are shown in Figure a. − Renormalization to the Mg–Mg bond was proposed to reduce the probability of miscalculation caused by the backscattering process and other disturbances. Based on the assumption that the local structural distortion affects the secondary pinning behavior, the p values of the pinning functions are plotted as a function of the relative bond ordering in Figure b.…”