Direct optical observation of Bloch lines and their motion in uniaxial garnet films using a polarizing light microscope

Abstract

Recently, the first direct optical observation of vertical Bloch lines using a laser scanning microscope has been reported (A. Thiaville, L. Arnaud, F. Boileau, and G. Sauron, EMMA Conference, Salford, Great Britain, 1987, paper AD-19). Here we describe a different way of direct observation that uses a polarizing light microscope. This method has the advantage of lower thermal disturbance of the domain structure and the ability of real-time observation. To obtain one-sided dark-field illumination, the incoming light beam is coupled into the garnet film by means of a glass microprism. On examining the Bi-containing film, the Bloch lines can be directly observed through the eyepiece of the microscope. Movement of Bloch lines caused by in-plane field pulses, and also by asymmetric bias field pulses, is observed.