Raman scattering study of RuSr2R2-xCexCu2O10+delta (R=Gd,Eu)

FAINSTEIN A, PREGLIASCO RG, WILLIAMS GVM, TRODAHL HJ

PHYSICAL REVIEW B - CONDENSED MATTER AND MATERIALS PHYSICS

Año: 2002 vol. 65 p. 184517 - 184517

0163-1829

We report a detailed Raman scattering study of polycrystalline samples of the magnetic superconducting ruthenocuprate RuSr2R2-xCexCu2O10+delta (R=Gd,Eu). Samples with varying Ce content (x=0.5,0.7,1.0) and with isotopically substituted O-18 have been studied. The assignment of the peaks is analyzed by comparison with the structurally related RuSr2RCu2O8 and Gd2-xCexCuO4 oxides. Additional phonon peaks not expected for the reported I4/mmm RuSr2R2-xCexCu2O10+delta space group are observed and are assigned to vibrations rendered Raman active by a symmetry reduction involving rotations of the RuO6 octahedra. In addition, for x=1 we observe several well defined spin-ordering-dependent features. As a function of decreasing temperature a diffusivelike contribution disappears and below the magnetic ordering temperature (T-M) an underdamped low-energy peak develops and shifts up to similar to130 cm(-1). A phonon line observed at similar to260 cm(-1) hardens, narrows, and strengthens strongly below T-M. Finally, a phonon line appears below T-M close to the O(Sr) A(1g) peak. All these features, which are also observed for RuSr2RCu2O8, interestingly do not appear for x=0.5. These results point into a structural distortion accompanying the magnetic order, and suggest a complex interplay of spin and lattice degrees of freedom in these ruthenocuprates.