Charge and Lattice Dynamics of Ordered State in La${}_{1/2}$Ca${}_{1/2}$MnO${}_3$: Infrared Reflection Spectroscopy Study

Abstract

We report an infrared reflection spectroscopy study of La${}_{1/2}$Ca${}_{1/2}$MnO${}_3$ over a broad frequency range and temperature interval which covers the transitions from the high temperature paramagnetic to ferromagnetic and, upon further cooling, to antiferromagnetic phase. The structural phase transition, accompanied by a ferromagnetic ordering at T${}_C$=234 K, leads to enrichment of the phonon spectrum. A charge ordered antiferromagnetic insulating ground state develops below the Néel transition temperature T${}_N$=163 K. This is evidenced by the formation of charge density waves and opening of a gap with the magnitude of 2${\Delta }_0$ = (320 $\pm$ 15) cm${}^{-1}$ in the excitation spectrum. Several of the infrared active phonons are found to exhibit anomalous frequency softening. The experimental data suggest coexistence of ferromagnetic and antiferromangetic phases at low temperatures.

4 pages, 5 figures

References in corpus (6)

• Colossal Magnetoresistant Materials: The Key Role of Phase Separation
• Phase diagram of the La${}_{1-x}$Ca${}_x$MnO${}_3$ compound for $0.5\le x\le 0.9$
• Raman and Infrared-Active Phonons in Hexagonal HoMnO${}_3$ Single Crystals: Magnetic Ordering Effects
• Magnetization studies of phase separation in La${}_{0.5}$Ca${}_{0.5}$MnO${}_3$
• Optical Evidence of Multiphase Coexistence in Single Crystalline (La,Pr,Ca)MnO3
• Temperature Dependence of Low-Lying Electronic Excitations of LaMnO_3

Cited by in corpus (1)

• Infrared absorption study of charge ordered $La{}_{0.5}Ca{}_{0.5-x}S{r}_{x}Mn{O}_3$ $(0.1\le x\le 0.5$