Coupling between flat films

Abstract

The magnetization distribution in a rectangular film, magnetized parallel to one side, is approximated by assuming that the magnetization <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">\overrightarrow{M}</tex> has the same direction everywhere in the film and that its magnitude rises from zero at the edge to the saturation magnetization M <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">s</inf> at a distance <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</tex> from the edge, maintaining this magnitude throughout the remainder of the film area. The function representing the magnitude of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">\overrightarrow{M}</tex> in the edge region is chosen in such a way that the resulting field has no singularities, <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</tex> is determined by the coercive force, which is set equal to the sum of the maximum demagnetizing field and an applied reversing field. This model lends itself better to the discussion of demagnetizing effects in single or coupled films than either the ellipsoid or the line-charge model. It takes account of the fact that the width of the edge region, where curling and domain walls occur, varies with the applied field, and, in this respect, it agrees fairly well with experiment. It, furthermore, permits the definition of a disturb sensitivity for memory elements consisting of single or coupled films.