Phonon Raman spectra of polycrystalline (La1-xSrx)2NiO4 crystals have been measured at room temperature and at liquid nitrogen temperature for x=0, 0.1, 0.2, 0.25, 0.3, 0.35, 0.4, 0.5. We have observed two Raman active phonons at about 450cm-1 and at about 240cm-1. We assign the mode at 450cm-1 to NiO stretching along c-axis (Alg) and that at 240cm-1 to optical oxygen along a- or b-axis (Eg). The frequencies of the Alg mode does not show a distinct Sr dependence. While the energy of the Eg mode strongly depends on x; with increasing x, the energy of the Eg mode decreases for x<0.3 and slightly increases for x>0.3. We have found that the x value of the minimum energy corresponds to the characteristic concentration, where the electronic conduction changes from semiconductive to metallic. We suggest that the Eg mode couples with the electronic state of (Lal-xSrx)2NiO4.
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics
- Energy Engineering and Power Technology
- Electrical and Electronic Engineering