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Magnetic Field Measurement

IP.com Disclosure Number: IPCOM000098009D
Original Publication Date: 1961-Nov-01
Included in the Prior Art Database: 2005-Mar-07
Document File: 2 page(s) / 38K

Publishing Venue

IBM

Related People

Middelhoek, S: AUTHOR

Abstract

The device measures magnetic fields based on rotational switching of the magnetization in a thin magnetic film. It is possible to precisely measure external magnetic fields with respect to both strength and direction.

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Magnetic Field Measurement

The device measures magnetic fields based on rotational switching of the magnetization in a thin magnetic film. It is possible to precisely measure external magnetic fields with respect to both strength and direction.

Three coils are placed in close proximity to a thin magnetic film element 1 which exhibits a uniaxial anisotropy in the easy direction epsilon. Driver coil 2 produces a magnetic field perpendicular to the easy direction epsilon and is connected to A. C. generator 3. A pickup coil 4 is connected, via amplifier and voltage rectifier 5, to zero instrument 6. Field compensating coil 7 applies a calibrated field and is connected to battery 8 and adjustable resistance 9.

The current through coil 2 is adjusted such that the generated magnetic driving field has an amplitude larger than the anisotropy field H(K) of 1. The magnetization of 1 rotates between both orientations in the hard direction under the influence of the driving field. When an external field with a field component H(epsilon), parallel to the easy direction, is present, the magnetization M rotates. This is either in the upper or in the lower half-plane, respectively, depending on the polarity of the external field. In this case, an A.C. voltage is induced in the pickup coil 4. When there is no external field component in the easy direction (H(epsilon) = 0), the magnetization of the film splits up and rotates equally, distributed in both half-planes, upper and lower...