Quasistatic Bubble Propagation in 1.5 μm Period Ion-Implanted Tracks for 64 Mbit Magnetic Bubble Memory Devices
Ion-implanted tracks with a 1.5 μm period for use in 64 Mbit magnetic bubble memory devices have been fabricated and operated. The bubble material used was (BiSmLu)3 (FeAl)5O12 garnet film, supporting 0.45 μm bubbles. The resist mask patterns for implantation were formed using a 1/10 reduction projection aligner, using rectangular patterns on a reticle. The bubble propagation tracks were fabricated by double deuterium implantation and annealed at 400°C for 30 minutes, with an SiO2 layer deposited on the garnet surface to stabilize the implanted layer. An operating bias field margin in excess of 7% was stably obtained in quasistatic bubble propagation. This shows that the ion-implanted devices have great potential for use in 64 Mbit magnetic bubble memory devices.
Design and characterization of ion-implanted tracks for 16 Mbit/cm 2 storage density bubble memory devices
The ion-implanted propagation tracks with contiguous disk patterns (CD tracks) have been confirmed to be better for high density propagation tracks (≥ 16 Mbit/cm2) than those with snake patterns (snake tracks), because of less interactions between bubbles on the other side in the same track. The CD tracks with 1.8 µm × 2.0 µm cell size for 0.5 µm bubbles have been evaluated. The large operating bias field margin of 12.4 percent is obtained at the quasi-static operation with rotating field H R of 60 Oe. The minimum rotating field is 40 Oe. Interdigital folded minor loops are proposed and operated. The proposed minor loops are composed of straight propagation tracks connected alternately to relax the in-side turns. The overall operating margin of 8.4 percent (46 Oe) is obtained at H R = 60 Oe. The feasibility of 16 Mbit/cm2storage density bubble memory devices is confirmed.
Determination of strain distributions in ion‐implanted magnetic bubble garnets applying x‐ray dynamical theory
X‐ray dynamical theory has been applied to determine strain distributions caused by ion implantation into magnetic bubble garnets. Experimental rocking curves obtained by a double‐crystal x‐ray diffractometer were compared with theoretical curves for assumed strain distributions, and after several trials, good fittings were obtained. It is shown that slight change in the assumed strain distribution leads to appreciable change in the theoretical rocking curve. Comparison between dynamical and kinematical treatments shows that dynamical treatment is more accurate. Applying the method, it was confirmed that strain by multiple ion implantation was basically the sum of those by single ion implantation.