Measurement of Kerr Rotation and Fresnel  Reflection Coefficients using a Rotating Polarizer Method

The magneto-optical Kerr effect (MOKE) occurs when polarized light reflects from a magnetized surface, causing a small change in the polarization angle and state. Measurement of the complex Kerr angle is well established and typically performed close to the null configuration in a polarizer-analyzer geometry [1]. In this work, we developed a method to measure the Kerr rotation and Fresnel reflection coefficients by varying the incident beam polarization angle and measuring the s- and p-polarized reflected light intensities using a Wollaston prism. We will present a Jones Matrix analysis of our setup as a function of the incident polarization angle and fit the equations to our experimental MOKE hysteresis loop data. In addition to being a multi-point analysis method, this process allows us to measure the Kerr rotation and the Fresnel coefficients, including the magneto-optic reflection terms. Using cobalt thin film as an example, we estimated the Kerr rotation of 1 mrad, |r_p/r_s|= 0.77, and |r_ps/r_s|=0.12 at a 45-degree angle of incidence. Such values will be compared with the literature and presented.

 

Reference:

[1]          D. H. Suzuki and G. S. D. Beach, “Measurement of Kerr rotation and ellipticity in magnetic thin films by MOKE magnetometry,” Journal of Applied Physics, vol. 135, no. 6, p. 063901, Feb. 2024, doi: 10.1063/5.0185341.