FTIR study of cerium doped electron superconductors R1.85Ce0.15CuO4 (R=Nd, Pr, Sm, Eu and Gd)

Systematic FTIR study of electron doped compounds of the T′-series are presented in this paper. Spectroscopic techniques are more sensitive than any other technique to the disorder due to doping in the structure. Polycrystalline ‘as prepared’ bulk samples, allows one to observe c-axis vibrations clearly, avoiding in-plane (a–b) polarizability due to charge carriers. Even though all R2CuO4(R=Nd, Pr, Sm, Eu and Gd) doped compounds belong to T′ structure, due to the different sizes of the rare earth ionic radii, the structure stabilization is very difficult to achieve since copper–oxygen distance vary from compound to compound and hence the phonon characteristic spectrum of the series. The role of apical oxygen in T-structure is discussed in detail from the point of factor group analysis and compared with the V-structure. The IR study of R2CuO4 (214) compound with Ce doping reveals the difference and similarities of the electronic properties between hole doping and electron doping when compared with T-structure compounds.