Simple Method of Measuring Mobility in Cylindrical Domain Materials

Abstract

A simple method is described for measuring wall mobility in materials which support cylindrical domains. The mobility is determined from the initial velocity with which a domain wall responds to a field step. A sample, which is demagnetized into the stripe domain state, is subjected repetitively to a fast rise‐time pulsed field. The displacement of the stripe domain walls is observed optically as the domains adjust to the new equilibrium configuration. In the particular case of viscous damping and negligible wall mass, for a field step H₀ which results in an equilibrium displacement x₀, the instantaneous displacement is x=x₀[1‐exp(‐ω_ct)], where ω_c is the ratio of the restoring force constant to the damping constant. The mobility μ=x₀ω_c/H₀. The time‐dependent displacement can be displayed graphically in a few minutes by a sampling technique. Measurements on TmFeO₃ yield results in good agreement with previous data. The mobility for DyFeO₃ is found to be 330 cm (sec Oe)⁻¹.