Apparatus for measuring the hysteresis loop of hard magnetic films on large magnetic recording disk

摘要

A magneto-optic Kerr effect hysteresis loop measuring apparatus is provided which employs a small relatively low weight ring magnet having a small gap and a high magnetic field strength in the deep gap and in the adjacent external gap. The spot on the product which is to be non- destructively tested is placed in the external gap field next to the small gap in a region of saturating magentic field. A laser beam having a high polarization ratio is directed along an incident path to the spot on the surface of the product to be non-destructively tested and the reflected beam is processed in a Kerr effect detector to provide hysteresis loop data which is capable of providing information sufficient to determine the squareness of the hysteresis loop and the coercivity of the material being non-destructively tested.