High-frequency propagation and failure of contiguous disk devices in an ion-implanted 3-μm YSmLuCaGe garnet film were investigated by using high-speed optical sampling. The minimum drive field, the bias field operating margin, and the bubble position with respect to the instantaneous rotating field direction were found to change with the frequency of the drive field. The shape and position of bubbles during the propagation were measured so that the instantaneous velocity dependence of the frequency of the drive field could be calculated. This study was done on a selection of different tracks so that the dependence of the geometry of the tracks could be included. It was found that more uniform instantaneous velocity leads to lower minimum drive field and a higher rotating frequency limit. The cause of high-frequency failure was examined and found generally to be the limitation of the maximum velocity of bubbles causing a phase lag greater than 90°. This limitation can be caused either by a low drive or by a saturation velocity.

Effects of helium ion double implantation on contiguous disk (CD) bubble devices have been examined by x-ray diffraction, FMR, and annealing techniques. The results were compared with static and dynamic performance of CD devices. Samples had a composition of SIllo.29 LUo.40 Y 1.42 Cao.89 Fe4.11 Geo.89 Ol2 with stripe width 3!Lm, He = 143 Oe and were implanted with 190-keV helium at 4.5x 10 15 He+ /cm 2 and 100-keV helium at 3 X 10 15 He + /cm 2 . X-ray diffraction curves show that He ion double implantation gives a more uniform strain profile with a main strain of 0.84% and a strain induced anisotropy field of 3100 Oe. FMR spectrum results show an implantation induced anisotropy field of 3185 Oe which is in good agreement with x-ray diffraction result. The main strain decreases linearly with the annealing temperature Ta extrapolating to zero at 1000 ·C. The implantation induced anisotropy field also decreases with T a , but exhibits an excess of 600 Oe over the strain anisotropy field. This excess is attributed to the suppression of growth induced anisotropy by He ion implantation. The measurements ofthe bubble collapse field and propagation margin on a CD track with 12-!Lm period at 100 kHz show that annealing at temperatures higher than 300·C causes the performance of CD devices to degrade very rapidly. The margin becomes narrow and the minimum drive field increases. Annealing above 500·C will kill the device.