Monitoring covered current paths in IC, thyristor, etc. - placing thin magneto=optic, anisotropic layer over body and detecting hysteresis effect of magnetic shield

摘要

A thin layer (4) of a material, which has magneto-optic characteristics is arranged on the open surface (2a) of the body (2) to be tested. The thin layer of material also has a magnetic anisotropy with a predetermined position of the light direction of the magnetisation and in the light direction of the light direction of the magnetisation. A magnetisation curve in the form of a bistable hysteresis curve has two curve branches with adequately high slope (DELTA M1/DELTA H). - The field strength of the magnetic field (Hs) produced by the current conducting paths (3) in the magneto-optic layer (4), is larger than the 0.3 times the interval (DELTA Hu) required for demagnetising the magneto-optical layer along each of the curve branches. The magneto-optic layer (4) is placed in a magnetic background field (Hh) so that demagnetising results along one of the curve branches. The magnetising position influencing the magneto-optic angle of rotation is made visible in the magneto-optic layer (4) as a contrast image (15) by means of a corresp. magneto-optic unit (14).