Slow Domain Wall Motion in Homogeneous Vacuum-Deposited Iron-Nickel Films

Abstract

An experimental study has been made of slow speed domain wall velocity as a function of switching field and temperature for a “homogeneous” vacuum‐deposited magnetic film using the Kerr magneto‐optic technique for visual and photographic velocity measurements. The deposited film was in the form of a circle, one centimeter in diameter and about 1500 A thick with a composition of about 78% nickel and 22% iron. In the film studied, domain walls continue in motion until the film is saturated without any increase in the applied magnetic field over that necessary to just nucleate the domain. The general expression obtained for the domain wall velocity as a function of applied field $H$ and temperature $t$ for a contained wall is ${\mathrm{V=\hspace{0.17em}V}}_0\mathrm{(t)\hspace{0.17em}}\exp {\text{\hspace{0.17em}8.8(H\hspace{0.17em}−H}}_0)$ , where $H$ is in oersteds and $V$ is in cm/sec. It was also determined that the domain wall velocity increases with increasing temperature at a fixed value of the applied magnetic field. The plotted data are nonlinear but in general the velocity increases with temperature at a rate greater than the first power of the temperature but less than the square of the temperature. Observations were made over a range of wall velocities from ${\text{3.4×10}}^{\text{−4}}\hspace{0.17em}\mathrm{cm}/\sec \hspace{0.17em}\mathrm{to}{\text{\hspace{0.17em}7.6×10}}^{\text{−2}}\hspace{0.17em}\mathrm{cm}/\sec$ .