Optimized designs of a 4 Mbit permalloy bubble memory device

New modified detector design and arrangement for 4 Mbit permalloy devices operating at 200 kHz and 60 Oe triangular driving field have been developed. The new detector gives the stable output signal waveforms for the variation range of the driving field of 45 Oe to 70 Oe and about three times larger output signal levels compared with that of a 1 Mbit device detector. A minimum required driving field, HRmin, limited by a ω-2ω transition noise at the detector is reduced by optimizing the direction of the detector lines with respect to a bubble holding in-plane field, HDC which is necessary for start/stop operation. By introducing this modified detector pattern and arrangement, we have realized the operation of the 4 Mbit permalloy devices with good characteristics at 200 kHz and 60 Oe triangular driving field in the temperature range of -5°C to 70°C.