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, θ
_K
, and ellipticity η
_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 Q
₀
of 130 Å thick Co film were used. However, θ
_K
, and η
_K
, decrease rapidly for films thinner than 40 Å, and fell nearly to zero for film thicknesses below about 18Å.