Specific features of the reflection of infrared radiation by crystalline dielectrics in a magnetic field

Magnetic-field-induced variations in the reflection spectra R(λ) of the crystalline dielectrics Al₂O₃, LiF, and MgO in the infrared band (λ = 2.5–25 μm) are investigated. It is found that the reflection spectra exhibit specific features in the neighborhood of wavelengths corresponding to the excitation of optical phonon modes in the above-mentioned crystals and that a magnetic field causes an appreciable variation in the reflectivity at these wavelengths. To qualitatively describe the effect of a magnetic field on the reflection of light, the magnetoreflection spectra ΔR/R are investigated. The spectra ΔR/R exhibit sharp peaks in the neighborhood of wavelengths at which the materials under investigation are characterized by minimal reflectivity. The values of ΔR/R for p-polarized infrared radiation in a magnetic field of about 12 kOe amount to about 0.5% for Al₂O₃ at λ ≈ 9.6 μm, 7% for LiF at λ ≈ 11.1 μm, and 0.07% for MgO at λ ≈ 11.7 μm.