Thin-Film Surface Bias on Magnetic Bubble Materials

A method of reducing the external magnetic bias field to maintain stable cylindrical domains (magnetic bubbles) in uniaxial orthoferrites or garnets is presented. A thin film of a permanent magnetic material is sputtered onto a platelet inducing an exchange coupling interaction across the interface. This interaction manifests itself as an effective bias field which reduces the external applied field required to stabilize bubbles. So far the largest effective bias obtained has been about 25 Oe, using Co3.2Cu1.3Fe0.5Ce0.25Sm0.75 sputtered onto a 15-μ-thick platelet of Sm0.55Tb0.45FeO3. Dynamic properties do not seem to be appreciably altered for low-speed operation in a T-bar rotating field device.