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Nondestructive Low Noise Measuring of Magnetic Properties of Magnetic Storage Media

IP.com Disclosure Number: IPCOM000086476D
Original Publication Date: 1976-Sep-01
Included in the Prior Art Database: 2005-Mar-03
Document File: 2 page(s) / 39K

Publishing Venue

IBM

Related People

Schneider, J: AUTHOR [+2]

Abstract

Utilizing the magneto-optical Kerr effect, the present measuring process serves to measure nondestructively the magnetic properties both of thin-film storage media and of particular layers. Special measures ensure that noise and background signals are largely avoided.

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Nondestructive Low Noise Measuring of Magnetic Properties of Magnetic Storage Media

Utilizing the magneto-optical Kerr effect, the present measuring process serves to measure nondestructively the magnetic properties both of thin-film storage media and of particular layers. Special measures ensure that noise and background signals are largely avoided.

The typical arrangement of the measuring set-up is shown in the figure. Magnetic layer 1 of a magnetic record carrier 2 is magnetized at point 3 by means of an electromagnet EM. At point 3 a laser beam LB is directed at an angle alpha through polarizer P. Polarizer P polarizes the incident laser beam LB either in the plane of incidence or linearly perpendicular thereto. Beam B reflected at point 3 is split in a Wollaston prism W into two light beams B1 and B2 polarized perpendicularly to each other. The main plane of Wollaston prism W is arranged at an angle of 45 degrees in relation to the direction of polarization of laser beam LB, thus yielding two equally intensive beams B1 and B2 polarized perpendicularly to each other. An analyzer A1 for beam B1, a lens L1, and a detector D1 as well as an analyzer A2 for beam B2, a lens L2, and a detector D2 are arranged in the peripheral cones of the area covered by the two beams B1 and B2. The two beam intensities are detected by detectors D1 and D2 (e.g., photocells) and are fed into a differential amplifier whose output signal is plotted on an XY recorder. For plotting the hysteresis curve, the difference signal detected is applied to the Y axis of the recorder, whereas a signal corresponding to the magnetic field of electromagnet EM is fed into the X channel.

As a result of the magnetization of magnetic layer 1 at point 3, the incident l...