Synchrotron X-Ray Absorption Spectroscopy (XAS) Studies on Structural and Magnetic Properties of T’-Pr_2-xCe_xCuO₄ Nanocrystals

Abstract

We have succeeded in synthesizing electron-doped cuprates T’-Pr2-xCexCuO4 (PCCO) with x = 0 and 0.10 nanocrystals prepared by the chemically dissolved method. Reduction annealing of the PCCO samples at 700°C under a flowing argon gas atmosphere has been performed for the removal of excess oxygen in the apical sites. The XRD data showed that the reduction annealing process decreases c-axis length indicating successful removal of the excess oxygen. The bond distortion of PCCO including coordination number and bond distance between the absorber atoms with the nearest neighboring atoms (Cu-O) was investigated by extended x-ray absorption fine structure (EXAFS) using Cu K-edge. The implication of our results is discussed on the basis of tremendous influence of oxygen vacancies on the magnetism of the nanosized T’-cuprates at the normal state.

Possible Defect Recovery in T’-Pr_2-<i>x</i>Ce<i>_x</i>CuO₄ with <i>x</i> = 0.10 Nanoparticles Analyzed by Neutron Diffraction

“…The present results support the finding of the disappearance of WFM behavior in PCCO nanoparticles as reported in Ref. [6,18]. The recovery of oxygen vacancy on the surface influences the number of crystalline defects which is probably responsible for the net magnetic moment at the surrounding Cu atoms.…”

“…This gives an idea of selfhealing driven through the oxygen diffusion mechanism during the annealing process. Regarding the previous EXAFS studies on T'-PCCO with x = 0.10 [18], there is an increase in R distance between the absorbance atom (Cu) and the in-plane oxygen atom (O(1)). This confirms a relatively small relaxation after the annealing in argon atmosphere.…”

A Structural Investigation of T’-Pr2-xCexCuO4 nanocrystals with x = 0.13

“…The existence of the crystalline defect [2,5], defect recovery [6], and the local structure [7] on this T'-type structure has been well studied in gaining a fundamental understanding of the structural behavior at room temperature. The structural studies at the under doped regime [5] and upper doped regime [2,8] of the T'-type cuprates have been explored in detail on the Ce-doping dependence in related to the crystalline defects due to annealing effect. Unfortunately, the detailed study of specific moderate tetravalent ionic doping has not been studied well.…”