Infrared properties of ferropericlase Mg1-xFexO:: Experiment and theory

The temperature dependence of the reflectance spectra of magnesium oxide (MgO) and ferropericlase (Mg(1-x)Fe(x)O, for x=0.06 and x=0.27) have been measured over a wide frequency range (approximate to 50-32 000 cm(-1)) at 295 and 6 K. The complex dielectric function has been determined from a Kramers-Kronig analysis of the reflectance. The spectra of the doped materials resemble pure MgO in the infrared region, but with much broader resonances. We use a shell model to calculate the dielectric function of ferropericlase, including both anharmonic phonon-phonon interactions and disorder scattering. These data are useful in understanding the vibrational properties of ferropericlase.