Infrared and Raman Study of (La_1-<i>x</i>Sr_<i>x</i>)₂NiO₄and La₂(Ni_1-<i>x</i>Cu_<i>x</i>)O₄

Abstract

Motivated by the observation of the close correlation between disappearance of the infrared absorption peak at about 680 cm -1 and the appearance of high- T c superconductivity in (La 1- x M x ) 2 CuO 4 (M=Ca, Sr, and Ba), we have measured infrared absorption spectra of (La 1- x Sr x ) 2 NiO 4 ( x =0.0, 0.01, 0.02, 0.03 0.04, 0.07, 0.10 and 0.15), La 2 (Ni 1- x Cu x )O 4 ( x =0.0, 0.20, 0.40 0.60, 0.70, 0.80, 0.85, 0.90, 0.95 and 1.00), and Raman spectrum of La 2 NiO 4 . No disappearance of the infrared absorption peak at about 680 cm -1 has been observed in (La 1- x Sr x ) 2 NiO 4 . By assigning the peaks to characteristic lattice vibrational modes, discussions have been devoted to the possible origin of the infrared anomaly.