Magnetic and Magneto-Optical Properties of Fe-Doped EuO Films

Abstract

EuO films with ∼8-wt% Fe have saturation magnetic moments of about 180 emu/g at 4.2°K and Curie temperatures (Tc) as high as 200°K (for pure EuO, σ=232 emu/g, Tc=69.5°K). The temperature dependence of the magnetization does not scale relative to pure EuO but deviates from the normal magnetization curve in that it exhibits a long tail extending from about 100°K up to Tc. Optical absorption data at 6°K in the range 0.3–2.5 μ indicate a characteristic peak at λ=0.6 μ (due to the 4f-5d transition) with α=2.2×105/cm, about 50% higher than pure EuO. The wavelength dependence of the normal Faraday rotation at 4.2°K is similar in shape to pure EuO; both peak at 0.7 μ but the peak rotation of the Fe-doped film (6×105 deg/cm) is about 30% lower than pure EuO. Mössbauer measurements of 151Eu show mainly Eu+ + with an isomer shift of −12.25 mm/s as in bulk EuO. At 4.2°K the 151Eu hyperfine field is 280.8±5.6 kOe (pure EuO≈300 kOe). The isomer shift of the doublet observed on the 57Fe resonance at 300°K is characteristic for metallic iron. We conclude that only a small fraction of the Fe is effectively doping the EuO films.