Infrared Transmission, Magnetic Birefringence, and Faraday Rotation in EuO

Abstract

We have measured the infrared transmission, magnetic birefringence, and Faraday rotation of EuO single crystals in the wavelength range between 2 and 20 μ. These effects have been studied as a function of temperature between 5° and 200°K in magnetic fields up to 9 kG. The most transparent samples have an absorption coefficient less than 0.5 cm−1 in the range between 3 and 9 μ and less than 1.0 cm−1 at 10.6 μ. The transmission decreases gradually at longer wavelengths and is largely independent of temperature and magnetic field except for shifts in the short wavelength absorption edge and effects of domain scattering at low temperature. Below the Curie point at about 70°K these crystals show a strong magnetic birefringence and Faraday rotation. At 20°K and 9 kG the difference in the index of refraction for light polarized perpendicular and parallel to the magnetic field is n⊥-n∥=1.07×10−2 at 10.6 μ and increases gradually to 1.5×10−2 at 2.5 μ. Under these experimental conditions the Faraday rotation is approximately 660 degrees/cm at 10.6 μ corresponding to nr-nl≃3.9×10−3. This rotation increases to about 2.5×104 degrees/cm at 2.5 μ. This corresponds to a specific rotation per unit attenuation in excess of 150 degrees/dB at 10.6 μ and 104 degrees/dB at 2.5 μ.