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Astroid Plotter

IP.com Disclosure Number: IPCOM000092790D
Original Publication Date: 1967-Feb-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 2 page(s) / 44K

Publishing Venue

IBM

Related People

Kump, HJ: AUTHOR

Abstract

The switching astroid of uniaxial thin films can be obtained from the cross-field loop (M(x) vs h(y)) electrically by assuming Slonczewski's tangent rule. This is discussed by M. Prutton in Thin Ferromagnetic Films, Pg. 59, Butterworths, 1964.

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Astroid Plotter

The switching astroid of uniaxial thin films can be obtained from the cross- field loop (M(x) vs h(y)) electrically by assuming Slonczewski's tangent rule. This is discussed by M. Prutton in Thin Ferromagnetic Films, Pg. 59, Butterworths, 1964.

The rule states that the tangent to the astroid, through the field point, defines the magnetization angle. While the rule is strictly valid only for ideal films, a reasonable accuracy is obtained even for highly dispersed films.

The parametric equations for the rotational astroid of ideal uniaxial thin films are given as:

(Image Omitted)

and the general equation as:

The rotational properties can be transformed from the h(x) vs h(y) plane to the m(x) vs h(y)d plane, the cross-field loop, through Slonczewski's tangent rule. Since:

The astroid can be reconstructed electrically from the cross-field loop using an analog computer arranged to calculate equations (4) and (5). A schematic of the computer is shown where the input can be taken from any loop tracer capable of generating the cross-field loop.

The cross-field loop is displayed on an oscilloscope where the gains of the scope are adjusted such that the loop approximates a circle scribed on the scope face. The input to the analog computer is taken from the plates of the scope so as to preserve the m(x) and h(y)d relative scales. The gains of the input stages of the analog computer are fixed such that the maximum excursion of m2 exactly equals the reference...