VELOCITY ASYMMETRY DURING STRIPE HEAD PROPAGATION IN ION-IMPLANTED BUBBLE GARNET-FILMS

Stripe head propagation has been investigated in ion-implanted garnet films using high speed photography with 10 nsec laser pulse illumination. For a given in-plane field applied along the stripe, the stripe head velocity increases linearly with drive until a peak drive is reached, beyond which the velocity drops. The peak velocity increases with in-plane field magnitude and depends on which of the two directions parallel to the stripe that the in-plane field is applied. Numerical calculations of the dynamic wall structure are made to predict the peak velocity as a function of in-plane field magnitude and direction. The effect of the implanted layer is taken into account by using a surface pinning condition. Results show that velocity breakdown occurs when a horizontal Bloch line (HBL) is nucleated. The velocity asymmetry with respect to in-plane field direction occurs because the HBL nucleates at opposite surfaces for the two in-plane field directions. The implanted layer inhibits HBL nucleation by pinning the surface spins, thus producing a higher peak velocity.