Nonlinearity of Faraday loops

Faraday loops traced with an extinction method and magnetization hysteresis loops were compared. When a material consists of a magnetic multidomain, the detected apparent Faraday rotation is not proportional to the net magnetization. In addition to this nonlinearity, light diffraction by domains results in loop deformation. The loop traced with a larger part of diffracted light has more nonlinearity than when it is traced using only the zeroth-order diffracted beam. An extreme case for the nonlinearity of Faraday loop tracing appears when the image of the domains of the material is formed on the photodetector. The nonlinearity increases for a material with a larger Faraday effect while the differential fixed analyzer method gives a loop without nonlinearity. It has been shown that the extinction method for identifying polarization is not helpful for examining the magnetization hysteresis instead of evaluating the magnetization loop itself