Observation of the transverse second-harmonic magneto-optic Kerr effect from Ni₈₁Fe₁₉ thin film structures

We report second-harmonic magneto-optic Kerr measurements on air-exposed, polycrystalline Ni₈₁Fe₁₉ thin films, ranging in thickness from 1 nm to 2 μm, on Al₂O₃ coated Si (001). For samples thicker than 20 nm, in the transverse Kerr geometry, we observe a factor of 4 change in second-harmonic intensity upon magnetization reversal. For thin samples, we observe interference between second-harmonic fields from the various interfaces and deterioration of ferromagnetism in the 1 and 2 nm films. Modeling suggests that the Ni₈₁Fe₁₉/Al₂O ₃ interface has a larger second-order susceptibility than the air/Ni₈₁Fe₁₉ surface.