R. Akimoto et al., ELECTRON-PHONON INTERACTION AT MAGNETIC EXCITON-STATE IN EUROPIUM CHALCOGENIDES, Journal of the Physical Society of Japan, 63(12), 1994, pp. 4616-4628
Temperature and magnetic field dependences of the photoluminescence sp
ectra of EuS, EuSe, and EuTe have been studied systematically. Photolu
minescence band having a nearly Gaussian line shape has been analyzed
by the configuration coordinate model, and the Huang-Rhys factors and
phonon energies for the relaxed exciton state have been determined for
the first time. From an oscillatory structure in the spectra, it has
been found that the magnetic exciton state couples with the LO phonons
strongly. Further, it has been found that the half-width of the photo
luminescence band changes depending on the phase transition from param
agnetic to antiferromagnetic or ferromagnetic phase, which has been in
terpreted by the change in the electron-phonon coupling strength due t
o the change in the spatial extension of the exciton wave function at
the magnetic phase transition.