Modification of local magnetic properties of steel surfaces by a Q-switched Nd:YAG laser beam

Using a Q-switched Nd:YAG laser, we have successfully obtained laser-induced ripple patterns on various ferric metal surfaces. Changes of magnetic properties associated with the rippled areas were then investigated using a simple magnetic detecting system, which consisted of an audio recorder head, an audio amplifier and an oscilloscope. Significant magnetic changes associated with the formation of the ripples were found on a steel substrate pre-coated with a layer of chromium. This technique can be used as the basis of a machine readable laser marking system on steel surfaces, or even other surfaces that could be cotated with a steel/chromium film.