Effects of Nuclear Radiation on Magnetic Bubble Domain Materials and Devices

This program was undertaken to provide an initial experimental assessment of radiation effects in available magnetic bubble-domain materials and devices. Permanent damage experiments were performed on three types of magnetic garnet films and on several types of device structures in both Co(60) gamma and nuclear reactor (neutron) environments. Materials tested were films of Ga:YIG, Ga:ErIG, and Ga:(YGdTm)IG. Properties measured were saturation magnetization, wall energy, defect density, optical transmission, domain wall mobility, coercivity, and saturation velocity. No change was found in these properties after approx 10 to the 15th power n/sq cm (1 MeV equivalent) or 50 Mrads (Si) of Co(60) gamma-rays. Device structures studied included Y-bar, T-bar, chevron, 2 bar chevron, and 3 bar chevron propagation loops and magnetoresistive permalloy domain detectors. Properties measured were propagation margins of the loops and magnetoresistive coefficient, coercivity, and dispersion of the permalloy detectors. No changes in these properties were observed on devices having hard bubble suppression after 50 Mrads (Co(60)) and approx 10 to the 15th power n/sq cm (1 MeV equivalent).