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 dx/dh_{p} of the displacement amplitude with respect to the peak drive field. This signal is the basis of plots produced automatically of dx/dh_{p} versus frequency (10 kHz - 32 MHz), dx/dh_{p} versus h p , and x versus h p . Data obtained on an epitaxial garnet film of Eu 0.7 Y 2.3 Fe 3.85 Ga 1.15 O 12 are presented showing domain wall resonances and nonlinearities between wall velocity and drive field.