Polarization rotation of reflected light from a magnetic surface
The Magneto-Optical Kerr Effect (MOKE) rotates the polarization plane of reflected light by a Kerr angle θ_K ∝ M (the magnetization), typically 0.01–1° for ferromagnets. In polar MOKE, normal-incidence light probes the z-component of M. Sweeping the external field H traces out the hysteresis loop: M(H) transitions between ±M_s at the coercive field ±H_c. MOKE is widely used to image magnetic domains.