Longitudinal Kerr Magneto-Optic Effect in Thin Films of Iron, Nickel, and Permalloy*

Abstract

The longitudinal Kerr magneto-optic effect can be characterized by four parameters n, k, Q0, and q. The first two parameters, n and k, are the ordinary optical refractive index and index of absorption, and the last two parameters, Q0 and q, are the magneto-optic amplitude and phase. These parameters were determined for opaque, high-vacuum deposited films of iron, nickel, and Permalloy for wavelengths between 0.360 and 0.620 μ. To find n, k, Q0, and q, the rotation and the ellipticity of the light reflected from the surface of these films were measured with a photoelectric ellipsometer. This ellipsometer employed a “Faraday cell” which sinusoidally rotated the polarization of the reflected light. To find the ellipticity, a calibrated retardation plate was placed in front of the Faraday cell. From the reflection coefficients derived by Voigt, the four parameters were computed from these data. As a check, the Kerr rotation and ellipticity for angles of incidence between 16° and 65° were then calculated from Voigt’s theory. These results compared satisfactorily with the experimental measurements at these same angles of incidence.The complex magneto-optic conductivity σ¯1 was calculated from the four optical parameters for each kind of film. The change of σ¯1real and σ¯1imag with the frequency of the incident radiation was compared with the predictions of Argyres’s theory. This comparison indicated that the predicted frequency dependence did appear in σ¯1real and σ¯1imag; however, the data extended over such a short frequency range that the results were inconclusive.