On the punch-through of Bloch loops in magnetic bubbles

Bubble translational motion in gradient drive fields has been carefully studied for both as-grown and ion-implanted films of (YEuTmCa) 3(GeFe)5O12 by using the rocking method. At a critical gradient amplitude which is found to depend on the drive pulse width, the motion of a bubble in an as-grown film becomes nonreproducible as evidenced by the fuzzy appearance of the bubble. Under the same critical amplitude drive condition, the skew angle of an S=1 bubble in an ion-implanted film decreases abruptly. This is attributed to punch-through of nucleated Bloch loops. The punch-through time was measured as a function of drive, and a reasonably linear relation between the inverse punch-through time and gradient drive field was found.