An improved BiYIG composition for one-micron bubbles

Robertson et al.1 have described a Ga-substituted BiYLuIG composition with very narrow linewidth, high Faraday contrast, and low coercivity. In this work, the temperature dependence of magnetic properties has been improved by replacement of the Ga in the above material by Ca,Si. The approximate composition of the improved material is Y1.9Bi0.5Ca0.6Fe4.4Si0.6O12, and it has a 4πM of 800 G at RT. The Curie temperature is 525 °K higher than that of the Ga-substituted equivalent. An anisotropy energy of 75 000 erg/cm3 and a stability factor Q of 3.8 have been measured. The temperature dependence of the collapse field was reduced from −0.35% to −0.22% per degree. The magnetostrictive coefficient λ111 was measured and used to estimate strain corrections to the anisotropy energy. The growth-induced anisotropy was correlated with Bi content. The Faraday rotation was measured at RT and at 1.4 °K over the range (1.5–2)×104 cm−1. In triply implanted films, bubble propagation has been observed on 4-μm period Ion Implanted Propagation Patterns with wide margins and normal symmetry properties.