Domain Wall Dynamics Measured Using Cylindrical Domains

Abstract

An experimental technique is presented for the measurement of the translational dynamic properties of a cylindrical domain held stable in a thin plate of uniaxial magnetic material by a bias field normal to the plate. A second field H_ROT, rotating in the plane of the plate at a frequency ω, saturates and rotates the magnetization in a circular Permalloy film parallel to and in close proximity with the plate. Interaction of the domain with the Permalloy disk pulls the domain underneath the edge of the disk and causes it to follow H_ROT around the circumference. The force driving the domain is proportional to the sine of the angle ψ by which the angular position of the domain lags behind H_ROT. For the rare‐earth orthoferrites, this drive force is balanced by a viscous drag proportional to ω and inversely proportional to wall mobility. For a sample of the mixed orthoferrite Sm_0.55Tb_0.45FeO₃, measurements of ψ at frequencies up to 225 kHz by stroboscopic observation of the domain showed the linear dependence of sin ψ on ω predicted by the viscous damping model and yielded a wall mobility of 970 cm sec⁻¹ Oe⁻¹ in agreement with measurements on the same sample using a previously published technique.