Transient bubble and stripe domain configurations in magnetic garnet materials

Abstract

Transient dynamic bubble and stripe domain configurations in magnetic garnet materials (Y1.57Eu0.78Tm0.65Ga1.05Fe3.95O12) has been observed using a stroboscopic optical microscope capable of making a series of single exposure 10 nsec pictures of the dynamic domain configuration at various times during and after the application of a 3 μsec bias field pulse that reduces the bias field. Wave-like distortions are observed in the widening stripe after approximately 1.5 μsec of initial uniform widening. This random distortion continues to grow until the end of the pulse. During the relaxation the gross shape of the stripe continues to become more distorted for the next couple of microseconds after the end of the pulse as the stripe attempts to return to its original narrow state. Random protuberances are observed on the wall at times as long as 10 μsec after the end of the pulse. Bubble domains in both implanted and non-implanted samples exhibit distortions as they are expanded and during relaxation. For moderate pulse amplitude, the bubbles grow and become distorted after about 1 1/2 μsec and exhibit characteristic but highly distorted shapes by the end of the 3 μsec pulse. Upon termination of the pulse as the bubble attempts to relax back in a bias field very near bubble collapse, the bubble takes on extreme yet characteristic shapes during relaxation. In nonimplanted material, some bubbles are much less affected by the pulse than others and are considered "harder". Conversions from "harder" to "softer" and "softer" to "harder" can be seen to occur typically taking one pulse to become hard and a couple of pulses to become soft.