PURPOSE: To test both the surfaces of a sample at the same time without any destruction by arranging the sample in the gap of a pair of pole pieces which have uniform magnetic flux density and generate high magnetic field intensity and are equal in magnetic pole polarity. CONSTITUTION: Lines of magnetic flux radiated by the surfaces of the magnetic pole pieces 51a and 51b having the same magnetic polarity repel each other and deflected along a passage parallel to the surfaces of the magnetic pole pieces 51a and 51b, so that the magnetic field becomes high intensity and uniform at the peripheries of the magnetic pole pieces. When the thin film magnetic layer 56 of a sample 57 is arranged between the magnetic pole pieces 51a and 51b in the uniform magnetic field area, the magnetic fields on the respective surfaces become uniform. When the top or/and reverse surfaces of the magnetic layer 56 are irradiated with a polarized laser beam 54, its reflected beam 59 is rotated in proportion to variation in the magnetic intensity of a spot 58 to be tested to show magnetic optical Kerr effect, so that the light beam is transmitted to a detecting device 53 through an opening part 62 and an analyzer 55. Similarly, the laser reflected beam on the other surface is sent to a detecting device 62 deg.. Consequently, both the disk surfaces can be tested at the same time without destroying the article to be tested or disturbing the manufacture line.
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