Study of the Magneto-Optic Kerr Effect of Co Ultra-Thin Films

A system for measurement of the surface magnetooptic Kerr effect (dubbed "SMOKE") has been developed. Measurement sensitivity is 5×10^¿4 degrees, and the absolute value of the rotation angle can be measured. The Kerr rotation, ¿K, and ellipticity ¿K, of Co thin films deposited on glass substrates in ultra-high vacuum were measured in-situ. When the film thickness was greater than 80 Å, experimental values were in good agreement with numerical calculations, in which the n, k and magnetooptic constant ¿0 of 130 Å thick Co film were used. However, ¿K, and ¿K, decrease rapidly for films thinner than 40 Å, and fell nearly to zero for film thicknesses below about 18Å.