Raman scattering from magnons and excitons in the 3-D ordered phases of CsCoBr3
1982; American Institute of Physics; Volume: 53; Issue: 11 Linguagem: Inglês
10.1063/1.330281
ISSN1520-8850
AutoresD. J. Lockwood, I W Johnstone,
Tópico(s)Solid-state spectroscopy and crystallography
ResumoHexagonal CsCoBr3 contains chains of Co2+ ions and exhibits three magnetic phases comprising a fully ordered triangular Ising lattice (T≲10 K), a partially disordered lattice (14 K≲T<28 K), and a disordered lattice that still retains significant intrachain spin correlations along the c axis. We have investigated the temperature dependence of the magnon and lowest excitons using Raman spectroscopy. For T≳30 K the magnon scattering appears as an asymmetric peak near 100 cm−1 superimposed on a broader band. On cooling, the spectrum is remarkable for the appearance of a series of discrete lines. The integrated intensities of prominent bands at 97, 102, and 105 cm−1 provide a measure of the 3-D magnetic ordering. The Co2+ excitons observed at 324, and 360, and 385 cm−1 in the 1-D phase each split into narrow components at the onset of 3-D order. For example, the 324 cm−1 band branches into lines at 322, 324, 327, and 329 cm−1. The relative intensities of the 324, 327, and 329 cm−1 lines have a similar temperature dependence to those at 97, 102, and 105 cm−1, respectively. The splittings of this exciton are one half that of the magnon indicating it experiences a smaller effective interchain exchange.
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