SMTMGA-GARNETS AND YSMTMGA-GARNETS FOR SMALL-BUBBLE APPLICATIONS

SmTmGa-garnet has a high growth-induced anisotropy, typical results being Ku = 1.1×105 ergs/cm3 and q = 7 for a sample with l = 0.20 μm. Thus the anisotropy of this material is high enough so that a high-q, 1 μm-diameter bubble material could readily be produced by properly adjusting the Ga content. Rocking experiments indicate that hard bubbles are successfully suppressed by ion implantation even though the implanted layer does not exert the same keepering effect as in lower anisotropy materials. Temperature dependence data show that (ΔHcol/H col)/ΔT at 50°C is only -0.24%/°C in the l = 0.20 μm sample mentioned above. The mobility of this sample is 140 cm sec -1Oe-1. The mobility can be increased (at the expense of reducing Ku and q) by adding yttrium to the composition. We have formulated such YSmTmGa-garnets for use as 2 μm bubble materials and have grown films with μ = 660 cm sec-1Oe-1, Ku = 2.3 × 104 erg/cm3 and μ = 340 cm sec -1Oe-1, Ku = 3.8 ×104 erg/cm3, depending on the yttrium content. An 11 μm-period symmetrical half-disc-type circuit fabricated on the latter film demonstrated an ∼20. Oe margin at 330 kHz with 50. Oe-peak triangular drive field.