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.