The influence of neutron and gamma irradiation in bubble garnet films

The behaviour of garnet films, containing 3 micronsbubbles, exposed to neutron irradiation and gamma rays is reported. The implanted and non implanted (YSmLuCa)3(FeGe)5O12epitaxial garnet films were irradiated with fast neutrons (10¹⁵n/cm²) and 10⁸rad (Si) gamma rays with 1 MeV energy. In these harsh conditions, the variations of physical characteristic parameters were analysed. In ion implanted films, the coercive field increased from 0.3 to 0.4 oe after neutron irradiation. The gamma rays irradiation brought the strip width back to the value it had before the ion implant. The anisotropy field increased slightly (3%) under both irradiations. The decrease in operating margins of 64 K bit memory chips is presented and a good correlation is made with the previous results. These effects are explained by general phenomena describing the interaction between the irradiation and the material. These experiments show that bubble memories will only fail at a high level of neutron and gamma ray exposure.