Magneto-Optically Measured High-Speed Switching of Sandwich Thin Film Elements

Abstract

A technique employing the Kerr magneto-optic effect has been used for measuring switching times as short as 10 nsec in thin ferromagnetic films, both individually and when coupled together in a sandwich structure. The switching speed of individual 1-mm-diam Permalloy bits has been found to be dependent on film thickness, the thicker bits switching more slowly. It was further observed that the time to switch 90% of a film is much more sensitive to film thickness than the time to switch 50% of the same film. When two similar films, magnetized in a head-to-tail fashion, are placed on either side of a drive line strip, the time to switch 50% of the films is essentially the same as for individual bits. However, the time required to switch 90% of the material is considerably shorter for sandwich elements than for the corresponding single bits. These results suggest that the slower switching of thick bits may be attributed to an incoherent rotational mechanism associated with the inhomogeneous demagnetizing field.