A measuring system for analyzing AC dynamic domain wall motions in bubble materials

A measuring system is described which is capable of rapidly analyzing dynamic ac domain wall displacements monitored by Faraday photometric signals from bubble materials placed in a polarizing microscope. An audio modulated rf drive field used in conjunction with signal processing electronics produces a signal proportional to the derivative of the displacement amplitude with respect to the peak drive field. This signal is the basis of plots produced automatically of versus frequency (10 kHz - 32 MHz), versus hp, and versus hp. Data obtained on an epitaxial garnet film of Eu0.7Y2.3Fe3.85Ga1.15O12are presented showing domain wall resonances and nonlinearities between wall velocity and drive field.