Radial expansion of bubbles and gradient bubble propagation experiments were conducted in a double layer garnet film with perpendicular anisotropy in both layers. Implanted and as-grown samples are compared. In radial expansion the side walls of the bubble exhibit a linear mobility much lower than calculated from γΔ/α. Saturation occurs at high drives (35 Oe). At drives above 50 Oe the saturation velocity of 27 m/s occurs only in the first 120 ns of the motion. After that the velocity drops to 17.5 m/s still independent of drive. This break in velocity does not occur in implanted samples, where the saturation velocity depends on implantation conditions. In gradient propagation saturation occurs at fields an order of magnitude smaller. The saturation velocity is independent of implantation, but overshoot depends strongly on it. No creep was detected. The 180° head-on domain wall between the two layers is found to have little effect on the dynamics of the side walls of the bubble. The motion of the head-on wall is also investigated and its velocity estimated. This head-on wall exhibits a linear mobility and a saturation velocity at high drives.

Dynamic behavior of domain walls in double layer self-biasing bubble garnet films

Herein disclosed is a laminated magnetic bubble device of a multiple layer structure composed of at least one thin magnetic film having low coercive force and vertically oriented anisotropy which can allow easy generation and erasure of a magnetic bubble, and at least one thin magnetic film having high coercive force and vertically oriented anisotropy which will not be affected by a magnetic field of low level used for generating the magnetic bubble in the thin film of low coercive force.

Laminated magnetic bubble device

Numerical solutions for domain‐wall dynamics are found which take into account interface pinning of magnetic moments at the boundary between sublayers of a multilayer bubble garnet film. Dynamic domain‐wall structure and velocity are calculated for drive field values up to 100 Oe. The effect of magnetic‐moment pinning at one or both of the bubble layer surfaces on the wall structure and its velocity is discussed. It is found theoretically that a form of stationary motion of the wall may occur when magnetic‐moment pinning is present even when the value of the drive is high. The results of the theory are compared with high‐speed photography data on bubble expansion in self‐biasing double layer garnet films and in ion‐implanted double‐layer self‐biasing (triple layer) films. It is concluded that the high drive stationary motion may occur in the ion‐implanted films and, also, that the exact structure of the sublayer accompanying the bubble layer is of secondary importance to domain‐wall dynamics in multilayer...

Effect of interface pinning in multilayer bubble garnet films on the dynamics of domain walls

Numerical solutions of the equations of motion of a flat, thin domain wall are solved with asymmetric boundary conditions. Absolute inhibition of the precession of magnetic moments is assumed at one film surface while force-free boundary conditions are assumed at the other film surface. The numerical calculations are shown to give good agreement with high speed photography data on the velocity of bubbles in radial expansion in double layer self-biasing films. A form of stationary motion at high drives is found.

Dynamics of domain walls at high drives with boundary conditions asymmetric due to magnetic moment pinning

Bubble wall states have been investigated in double layer garnet films. All seven wall states which exist in ion-implanted garnet films also exist in the double layer films. In the double layer films, two of these states (1/2,2, 1) and (1,2,2) cannot be obtained by translating the bubbles but are sometimes formed during nucleation. The transition S=0\rightarrow 1 cannot occur during bubble translation but can be produced by radial motion of the bubble wall due to a bias field pulse. The collapse field of S=1 bubbles is 1 Oe higher than that of S=0 bubbles. The results of wall state coding in a device using permalloy elements are described.

Study of wall coding in a 180&#176; capped double layer LPE film

Wall state transitions and stability measurements were performed on a series of double-layer films which contain 2μm bubbles. The film comprises a capping layer with uniaxial anisotropy but low saturation magnetization and a bubble layer with high saturation magnetization. Both types of domain wall states, "0" and "1", are found to be stable over a wide range of in-plane field values and even down to zero field. A theoretical explanation of the domain wall transitions and structure is also given. For bubble lattice devices, the new composite films may remove the in-plane field constraints on device functions imposed by the bubble wall states.

H. Hu

Papers

Wall state stability of bubbles in uniaxial double-layer LPE films