Optimum Design Consideration for Dual Conductor Bubble Devices

A design for dual conductor, current-access bubble devices with 8-μm periods has been optimized with a numerical calculation method for bubble motion in a propagating magnetic field, generated around hole patterns in conductor layers. Magnetic bias field distributions are calculated for an oval hole chain in the conductor layers. Bubble motion equations are obtained with analytical field distribution functions approximating the calculated field distributions. Minimum drive current density Jmin for normal bubble propagation is determined by a solution to the equations. The hole shape has been optimized by the minimization of the drive power the product of jmin and conductor resistance, which is calculated from current distributions around the hole pattern. Optimum layer thicknesses have also been obtained for 8μm period bubble devices. Both registration tolerance between the two conductor layers and bubble skew effects have been studied semiquantitatively on the basis of the equations of motion. The numerical calculation method developed here is found to be a highly effective means to optimize pattern design for smaller period devices.