Radio-Frequency Determination of New Growth-Induced Anisotropy in Garnets for Bubble Devices

Abstract

A new type of magnetocrystalline anisotropy has been observed under {110} faces in several fluxgrown mixed rare-earth iron garnets. This anisotropy is different in direction and magnitude from that previously reported in similar garnets under {211} faces. In Eu2ErGa0.6Fe4.4O12 with 4πM near 350 G at 300°K, microwave resonance measurements have shown that {110} face material has a large effective uniaxial anisotropy. The [100] in the growth plane is the easy axis, [011] normal to this plane is medium, and [011̄] parallel to this plane is hard. Using a resonance equation appropriate to the orthorhombic magnetic symmetry and neglecting the relatively small cubic terms, the effective uniaxial anisotropy field is ∼1300 Oe. This anisotropy leads to a new cutting procedure (type 3 cut) for bubble devices: {100} platelets are cut normal to the natural {110} faces. Using 15-μ-thick platelets of this type, bubbles ∼8μ in diameter were propagated. The domain wall mobility is ∼170 cm/sec/Oe. These properties are comparable to those of {111} platelets cut under {211} surfaces of the same crystals.