Browse Prior Art Database

Magnetic Field Measurement

IP.com Disclosure Number: IPCOM000090199D
Original Publication Date: 1969-Mar-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 2 page(s) / 36K

Publishing Venue

IBM

Related People

Hutchison, JD: AUTHOR [+2]

Abstract

A scanning electron microscope can be used to measure local magnetic fields and gradients in situations where the field is essentially constant in one direction. Field source 2 is held by support 4 so the direction of constant field is parallel to scanning electron beam 10. After passing source 2, beam 10 traverses a drift space 6 before converging to a focus on reference surface 8. This surface is normal to beam 10 and can be at surface having a known physical structure. For convenience in measurement, grids or diffraction gratings represent preferred structures.

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Magnetic Field Measurement

A scanning electron microscope can be used to measure local magnetic fields and gradients in situations where the field is essentially constant in one direction. Field source 2 is held by support 4 so the direction of constant field is parallel to scanning electron beam 10. After passing source 2, beam 10 traverses a drift space 6 before converging to a focus on reference surface 8. This surface is normal to beam 10 and can be at surface having a known physical structure. For convenience in measurement, grids or diffraction gratings represent preferred structures.

In the absence of local magnetic fields, beam 10 generates a micrograph of surface 8 conventionally. When fields are present, for example from object 2, the field components parallel to surface 8 produce distortions of the micrograph of surface 8. The distortions are quantitatively related to the direction and magnitude of the local fields.

In a similar arrangement, magnetic field gradients can be detected and measured by observation of astigmatism in the micrographs of the reference surface. A micrograph of a surface of regular granularity is distorted by the field gradient into lines of equal astigmatic correction. The lines of equal astigmatic correction appear similar to field lines. Using a calibrated focus control, the separation between the two astigmatic focal planes is found. The magnitude of the field gradient can then be calculated exactly as it is proportional to t...