In bubbles carrying at least 100 Bloch lines, called superhard bubbles, the phenomenon of static conversion of the Bloch wall has been observed. Two experiments will be described in detail: (i) the dependence of the number of Bloch lines as a function of the temperature at which the material has been treated and (ii) the phenomenon of the self-collapse of bubbles having Bloch lines in a supercompressed state.

New functional elements have been tested for 16 μm-period current-access circuits in single and double mask structures. Improved propagate patterns exhibit 15% operating margins at 1 MHz frequency and 20 mA current. Heat dissipation drops to 0.3 mW per conductor period. In conventional CaGe-garnet films it has been possible to increase the maximum frequency to 1.9 MHz at 60 mA. In the first orthorhombic films to be processed, 4 MHz has been reached already at 20 mA current. High-frequency current-access stretching of bubbles prior to detection is discussed. Operating margins of 10% are obtained up to 700 kHz in a pattern that stretches bubbles normal to their propagation direction. High-frequency writing is obtained by combining a number of field-access generators with an annihilator in the conductor track. A compact current-field-access swap gate allows the closest possible packing of the field-access minor loops. These elements have not yet been combined for the same conductor structure. In principle, however, the functions required for a field and current-access major-minor loop chip are now available.

A highly sensitive magnetic bubble detector in an essentially singlemask overlay ABSTRACT Bubble propagation has been investigated in conductor structures on 5 /.lm-bubble (Y, Sm, Lu, Ca)3(Fe, Ge)5012' The conductors consist either entirely of permalloy or of a sandwich of permalloy on gold. A static in-plane field is used for unidirectional bubble propagation.The dependence of bubble motion on current amplitude and inplane field magnitude has been measured at low and high frequencies.The bubble motion was observed to consist of a first slow step where the current acts against the in-plane field, and a second quick step where both act together. Attainable frequencies increase with increasing in-plane field and current intensities up to a maximum of 1.1 MHz. The sandwich conductor has a 12% operating margin at 830 kHz frequency and 30 mA current. It performs better than the ali-permalloy conductor at the same overall spacing of the permalloy to the epifilm.An improved transfer gate from current to field-access has an 18% margin, from field to current-access 16%, at 100 kHz. The overlap with the conductor margins is 7% at in-plane fields from 30 Oe. The gates can be combined to obtain a field-current swap gate.