COMPARISON OF 8 MIXED GARNET SYSTEMS FOR 7 MU-M-PERIOD BUBBLE-DEVICES

An extensive investigation of eight mixed garnet systems, totally 22 compositions with the same l values (0.2μm), was carried out for realization of high bit density bubble memory chips employing 1.8μm diameter bubbles in 7μm-period devices. The eight systems are YSmLuCaGe, YSmTmCaGe, YEuLuCaGe, YEuTmCaGe, YSmLuGa, YSmTmGa, YEuLuGa and YEuTmGa garnets grown on (111) GGG substrates. In order to fill in the material gap between Sm- and Eu-based garnets, YSmEuLuCaGe and YSmEuTmCaGe garnets were also studied. Comparison was made with respect to static (4πMs, Ku, HK, TC, A) and dynamic (μw, cursive-theta sign) properties, as well as Hco1 temperature dependence. Q-factor was varied by changing rare earth content ratio, but l and film lattice parameters were left essentially unchanged. From the dynamic and temperature properties viewpoints, it was revealed that YSmLuCaGe, YSmTmCaGe, EuLuCaGe, YSmEuLuCaGe, and YEuTmGa garnet systems are candidate materials, with l=0.2μm and Q≃4, for practical applications which utilize 7μm-period patterns.