Advanced Laboratory Course

Magneto-optic Kerr effect (experiment number 53, 2 days)

Our group offers a 2-day experiment on the subject of magnetism within the framework of the advanced laboratory course.

With rewritable mini-discs, you can listen to your favorite music while shopping or driving. The memory technology is based on the magneto-optic Kerr effect. The information is optically written and read with the methods of laser technology. In addition, the magneto-optic Kerr effect provides the widest application in the methodology for the investigation of magnetic properties of solids. Magneto-optical measurement methods are used in research and industry to investigate hysteresis curves, time-resolved magnetization processes (switching speed) and micro-magnetic behavior (magnetic domains, Weissian districts).

Magneto-optical effects describe the changes in the polarization properties of the light under reflection (Kerr effect) or transmission (Faraday effect) at magnetized samples. The rotation of the light polarization vector can be explained by the following model: Polarized light is an electromagnetic wave, in which the electric field vector oscillates in a plane. The oscillating electric field stimulates the electrons to vibrate at the surface of the solid state, so that they emit dipole radiation (see also keyword: Brewster’s angle). Due to the Lorentz force, the electrons are deflected in the magnetic field. As a result, the oscillation plane of the electrons and thus also the polarization plane of the reflected or transmitted light is rotated.

The aim of the lab-course experiment is to determine the influence of the magnetization of a reflecting metal surface on the polarization properties of the reflected light. The experiment consists of two parts. A Kerr magnetometer as well as a Kerr microscope with which one can visualize the magnetic domains of a reflective surface.

Information on the functional principle of a Kerr magnetometer

The script for the experiment is available for download under "Downloads" on the left hand side as well as on the website of the advanced laboratory course.