Design of 2 µm-period minor loops in hybrid bubble memory devices

The folded minor loops for hybrid bubble memory devices with 2 μm period propagation tracks have been developed by designing junctions between permalloy and implanted tracks, as well as designing inside and outside turns. The junction from the permalloy to the implanted tracks has been successfully designed utilizing the deep potential well of the permalloy pattern for bubbles to cross the boundary. The junctions were operated successfully for the first time using 0.6 μm bubbles optimized for 2 μm period tracks. We also designed the outside and inside turns considering the demagnetizing field and the crystalline axis of the implanted layer respectively. As a result, good bias margins of turns were obtained. The bias field levels of all elements agreed quite satisfactorily. Overall bias field margins of 40 Oe has been obtained with the quasi-static drive field of 70 Oe.