Observation of vertical Bloch line propagation

Abstract

The presence of vertical Bloch lines in the wall of a stripe domain of a magnetic ‘‘bubble’’ material can be inferred by observing the transient distortion of the straight wall driven by a uniform field. Because the local mobility depends upon local structure in the wall, rapid motion of the straight wall results in transient bulges of the wall. These hard wall bulge sections were seen by applying a large uniform bias field pulse and then observing the transient shape of the initially straight wall using a high speed optical sampling microscope with 10 ns pulse laser illumination. Bulge phenomenon, such as generation, annihilation, and propagation along the stripes were observed in an as-grown sample, Sm0.4Y2.6Ga1.15Fe3.85O12 with a thickness of 6.26 μm, 4πMs=125 Oe, γ=1.54*107 Oe−1, Hk=2190 Oe, α=0.208, and Q has a value of 17. Several different types of bulges have been seen. They can be different in size and can appear either on one side or both sides along the stripe domains. Shorter bulges usually move more slowly and inconsistently. They can be collected in the stripe bend and become longer bulges. Two bulges traveling in the opposite directions along the same stripe will combine into a shorter one or disappear.