SUB-MICRON DIAMETER BUBBLE-FILMS OF LU-SUBSTITUTED EU-IRON AND SM-IRON GARNETS ON (111) AND (100) ORIENTED NDGG, SMGG AND GDGG SUBSTRATES

Lu (a small ion) is substituted for Eu and Sm (large ions) to satisfy the film/substrate lattice match requirements for iron garnet films grown by isothermal LPE on three different rare earth gallium garnet substrates oriented (100) and (111). Epifilm growth rates, f, are relatively insensitive to growth temperatures, Tg, over a range of Tg ≃820 to 870°C, for the melts used. The value of f depends inversely upon the relative Lu content of the melts with slightly faster growth occurring on (100) than on (111). For (111) films maximum anisotropy energy, Ku, is obtained when large- and small-radius rare earth ions are approximately equal in concentration. These films with maximum stability factor, Q, can be grown on (111) SmGG. In contrast, (100) films have maximum Ku when the largest amount of Sm or Eu is present as in the case of films on NdGG(100). The Ku values for the (100) films are more sensitive to both Tg and film rare-earth concentration than those for the (111) films. Sm-based films have higher saturation magnetization, 4πMs, than Eu based films which results in smaller characteristic lengths, ℓ of 0.04 to 0.06 µm for Sm, compared to an ℓ of 0.06 to 0.12 µm for Eu-based films. The Sm-based films have higher domain wall damping coefficients and g factors than Eu-based films. This high damping reduces bubble mobility, whereas the high g factor is expected to increase bubble saturation velocity. © 1978 IEEE