Jahn-Teller Distortions Cooperating with Magnetic Interaction in the Raman Spectra of La0.75Ca0.25MnO3 Thin Film

摘要

Remarkable changes (additional peaks, frequency shift, and peak width) of Raman spectra of a La0.75 Ca0.25MnO3thin film have been observed during the paramagnetic insulator-ferromagnetic metal transition. The v1 band (230cm-1) hardens by lattice contraction as a result of the rearrangement of MnO6 octahedra. The JahnTeller distortions seem to be responsible for the broadening ofv2 band (485cm-1) above the magnetic transition temperature Tc. It is proposed that the 438cm-1 vibration mode activated in the magnetic ordering state is associated with the rearrangement of MnO6 octahedra. The softening of v3 band (610cm-1) below Tc can be ascribed to the magnetic interaction that brings into spin-phonon coupling terms.