Crystal structure and electronic properties of the oxygen deficient Sr$_{3}$Ru$_{2}$O$_{7-y}$ (0$\le $y$\le $0.5) ruthenate

In this work a study of the structural properties of the new non-stoichiometric Ruddlesden-Popper type Sr$_{3}$Ru$_{2}$O$_{7-y}$ compounds is presented. Sr$_{3}$Ru$_{2}$O$_{7-y}$ ($y$ = 0.17, 0.23, 0.28, 0.40 and 0.47) were synthesized by hydrogen reduction of the parent Sr$_{3}$Ru$_{2}$O$_{7}$ ruthenate. Rietveld structure refinements were performed to determine the crystal structure of the reduced compounds. Oxygen content of the samples was studied by redox chemical titration and ESR spectra confirmed the presence of Ru$^{3+}$. Removal of oxygen atoms from the parent compound results in shrinkage of the $c$ and growing of the $a$ lattice parameters, which we related to the Ru$^{4+}$ to Ru$^{3+}$ partial reduction in Sr$_{3}$Ru$_{2}$O$_{7}$. On basis of DFT calculations, with WIEN2k code, we compared the electronic properties of reduced and stoichiometric compounds.