The Eu-chalcogenides, EuO, EuS, EuSe, and EuTe exhibit remarkably large magneto-optical effects in the visible and infrared spectral regions arising from highly polarized europium 4f7 → 4f65d optical transitions. Faraday rotations as large as 8.5 × 105 deg/cm have been observed in EuO at 20° K and a wavelength of 0.7 µ, comparable to the value observed in iron. However, in contrast to the metallic ferromagnets, the Eu-chalcogenides are relatively transparent in this wavelength region. For example, at 0.75 µ and 4.2°K EuSe has a Faraday rotation of 1.4 x 105 deg/cm and an absorption coefficient of only 66 cm-1. This results in a specific rotation per unit attenuation of 500 deg/dB, approximately four orders of magnitude greater than that of iron. In the infrared, at energies below the semiconducting band-gap, the absorption is less and the specific rotation per unit attenuation can be even larger. The specific rotation of EuO at low temperatures is in excess of 2 x 104 deg/dB at 2.5 µ and 230 deg/dB at 10.6 µ These materials also exhibit remarkably large Kerr effects with longitudinal Kerr rotations as large as 2ϕ = 2.1° being observed in EuO at 12°K, 0.56 µ and 30° angle of incidence. The Kerr effects can also be considerably enhanced by antireflection coating and/or by depositing the film on a mirror substrate. These very large effects are of considerable technological importance and the possible use of the Eu-chalcogenides for magneto-optical memory systems, amplitude and phase modulation of light beams and optical isolators for laser systems will be briefly indicated.
Faraday Rotation Kerr Effect Specific Rotation Metallic Ferromagnet Mirror Substrate
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