International Business Machines Corporation

Pieter Dekker

John Casimir Slonczewski

Bernell E Argyle

Magnetic bubble domains are propagated in a magnetic medium in a desired direction using magnetic fields which have no spatial gradients. This is in contrast with conventional propagation techniques where magnetic overlays have to be used with applied magnetic fields in order to move domains. Depending upon the wall magnetization configurations in the domains, these domains are propagated by using, for example, a combination of a steady magnetic field and a magnetic field which varies with time, such as a pulse field or a sinusoidal field. This type of propagation is termed automotion. Bubbles which can automote are generated and detected in the magnetic medium using the principles of automotion. Embodiments are shown for representation of information using different types of bubbles, and in particular it is shown how to discriminate among bubble domains having wall configurations having a common winding number s. In a particular embodiment, a modulated bias field is superimposed on a steady magnetic field in the plane of the magnetic medium. Depending upon the direction of the in-plane magnetic field and upon the wall magnetization configuration of the bubbles, the bubbles can be made to move in different directions regardless of the directions of the modulated bias field.

Gradientless propulsion of magnetic bubble domains

Magnetic bubble domains are propagated in a magnetic medium in a desired direction using in-plane magnetic fields which are time varying but which have no spatial gradients. In applications such as information storage, the need for conventional propagation structures, such as offset conductor loops, patterned magnetic elements, and patterned ion implantation regions is reduced. Bubble domains having unwinding pairs of Bloch lines in their wall magnetization can be moved by applying appropriate in-plane magnetic fields, without the need for spatial gradients or variations in the magnetic field normal to the plane of the magnetic medium. The continuous movement of these bubble domains occurs by a cyclic process where the Bloch lines switch between two configurations, in an asymmetric way in response to the time varying in-plane field.

Gradientless propulsion of magnetic bubble domains using modulated

A technique for controllably providing state conversions between bubble domains having a common winding number S is described. In particular, controlled conversions between bubble domains having winding number S=1 is achieved by the application of spatially invariant, homogeneous magnetic fields. For the conversion of .sigma. bubbles (having two vertical Bloch lines) to .chi. bubbles (having no vertical Bloch lines), an in-plane field is not required and only a time varying perpendicular z-field is used. For conversion of a .chi..sub.+ bubble to a .chi..sub.- bubble, and vice versa, a time varying field pulse is applied, there being no requirement for an in-plane magnetic field. However, for the conversion of .chi. bubbles to .sigma. bubbles, an in-plane field is used simultaneously with a time varying z-field. For all controlled conversions, the applied magnetic fields do not have spatial gradients. The magnitudes of the applied magnetic fields and the rise and fall times of the z field are controlled within certain ranges in order to have controlled conversion of one state to another.

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Kortenhoef, Netherlands

Pieter Dekker