Operating Bias Field Adjustment of Bubble Propagation Tracks on Ion Implanted-Permalloy Hybrid Type Magnetic Bubble Memory Devices

Abstract

In ion-implanted and Permalloy hybrid bubble memory devices, the operating bias field region of ion-implanted tracks is lower than that of Permalloy tracks when the cell size is less than 4μm × 4μm. This reduces the overall bias field margin. The operating bias field region of Permalloy tracks has been shifted using the garnet film thickness dependence of a bubble collapse field. Thickness of a garnet film under Permalloy tracks is reduced using the ion-milling technique. The ion-milled region has a low coercive field and shows a good bias field margin. It has been confirmed in hybrid bubble memory devices with a 3.5μm × 3.5μm cell size that the operating bias field adjustment made by thinning a garnet film can improve the overall bias field margin.