as observed by Michael Faraday in 1845.
The magneto optical effects are characterised by the Kerr effect being proportional to the magnetisation. This makes it particularly useful in the study of surface magnetism since it is highly sensitive to the magnetisation within the skin depth region, typically 10-20nm in most metals [Bland et al (1989)]. The effect has been utilised to obtain hysteresis loops or domain images and is a relatively simple technique to implement.