Raman spectroscopy of RuSr_2(Eu_(1.5)Ce_(0.5))Cu_2O_(10) magneto-superconductor

摘要

Raman spectroscopy studies are reported for the RuSr_2Eu_(1.5)Ce_(0.5)Cu_2O_(10) (Ru-1222) compound at various temperatures of 300, 250, 200 and 90 K. Three distinct vibrational bands: the first at 110, 140, and 160 cm~(-1), the second at 295 and 347 cm~(-1), and third one at 651 cm~(-1) are seen in Raman spectra of the compound at room temperature. These bands are attached to the Cu atoms' c-direction, the Ru atoms' ab-plane stretching and Ru atoms' c-direction anti-stretching modes. Below 200 K, an extra vibrational mode is also seen at 260 cm~(-1). Also, with a decrease in temperature, though the Cu vibrational modes remain intact, the Ru atoms' αb-plane stretching (295 cm~(-1) ) and c-direction anti-stretching (651 cm~(-1)) modes shift gradually to higher wave number positions. The frequencies of modes at 260 and 651 cm~(-1) showed anomalous softening and line-width broadening below 100 K that corroborates well with the spin ordering seen in susceptibility studies. The studied compound is a ferromagnetic superconductor with magnetic ordering of the Ru spins at 200 K and superconductivity below 30 K. A magnetic and electrical transport characterization of the compound is also presented briefly.