A comparative Mössbauer study of the Nd_1+xBa_2 x(Cu_0.97⁵⁷Fe_0.03)₃O_zsolid solution: the role of low-temperature treatment

Abstract

Local structure features of the Nd1+xBa2−x(Cu0.9757Fe0.03)3Oz solid solution with various oxygen contents and cation compositions were examined for the first time by Mössbauer spectroscopy to explore the effects of cation disorder in the cases of the anomalous pseudocubic x = 0 phase, the x = 0.6 tetragonal solid solution with Nd stochastically substituting Ba and also the x = 0.9 orthorhombic phase with superstructurally ordered Nd and Ba. A new spectral component characterized by an isomer shift and quadrupole splitting was found for all the cases, evidencing the formation of associated defects such as ‘Fe(IV)Cu1O6–NdBa’ and confirming antistructural disordering of Nd3+ and Ba2+ in low-Tc NdBa2Cu3Oz samples.

Disordering effects in the atomic structure of fine-crystalline HTSC YBa2Cu3O y

“…In addition, the similarity in the realization of structure defects in fine crystalline YBa 2 Cu 3 O y and in NdBa 2 Cu 3 O y samples studied in [10,21] cannot remain unnoticed. In these publications, the structure of NdBa 2 Cu 3 O y was also formed in analogous high rate nonequilibrium conditions, and the authors of [10,21] also noted the slow dynamics of ordering of neodymium and barium cations as a factor generating…”

“…Neutron diffrac tion has made it possible to confidently analyze the effects associated with the redistribution of cations and oxygen in the cell (the possibility of taking into account the importance of these effects has been indi cated earlier). For example, a certain extent of mutual substitution of the rare earth cation and barium and simultaneous variation in the occupancy of the oxygen positions was hypothesized in [4,5,10]. However, information about these effects was obtained using macroscopic methods and Mössbauer spectroscopy, which did not provide direct answers to these ques tions.…”