¹⁵¹Eu Mössbauer spectroscopy and x-ray-diffraction studies on the Pb₂Ba₂EuCu₃O_8+δ system

Simultaneous replacement of Sr by Ba and Y by Eu in the Pb-2213 system was found to yield single-phase Pb2Ba2EuCu3O8+ samples, suitable for Eu151 Mössbauer measurements. The samples were synthesized by a solid-state reaction of metal oxides and carbonates under an inert atmosphere. An oxygen-rich sample corresponding to =1.79 was obtained by annealing the as-synthesized material (=0.16) in oxygen. The oxygen annealing increased the size of the lattice constants and led to an orthorhombic-to-tetragonal phase transition of the structure. The samples were also oriented in an 11.7-T magnetic field. The x-ray-diffraction spectra showed that the c axes tended to orient perpendicular to the applied field. The measured Mössbauer spectra exhibited an electric quadrupole interaction typical of the Eu site in high-Tc cuprates. The average orientation angles obtained from fittings of the Mössbauer spectra were in accordance with the results from the x-ray-diffraction measurements.