A comparison of frequency limited bubble device performance and material characteristics

We have observed the propagation margins as a function of frequency and temperature for a simple half-disk type test circuit fabricated on an (YSmLuCa)
3
(FeGe)
5
O
12
film. We have also measured the temperature dependence of the stripe width, anisotropy field, collapse field, mobility and dynamic coercivity. The frequency dependence of the margin demonstrates that in this circuit, the material is velocity limited above 300 kHz. In the range -20°C to +60°C, the upper and lower margin limits at a given frequency track the collapse field. Over this same temperature range, the mobility varies from 500 to 850 cm/sec-Oe and we conclude that the mobility is not the parameter which limits the device performance. The calculated saturation velocity is independent of temperature in this region and we propose that it is responsible for the failure of the circuit at the highest frequency. In the range from -20°C to +60°C, the coercivity becomes appreciable and the circuit performance deteriorates due to a decrease in the effective drive field.