Domain drag effect in the presence of variable magnetic field or variable transport current

Publisher Website
Google Scholar
Abstract
The predicted dragging of ferromagnetic domain walls by hydromagnetic forces generated by a current crossing the walls has recently been observed in amorphous Gd‐Co‐Mo films. We extend the basic theory to the case where a uniform external field parallel to the easy direction is changing the sample magnetization. Dragging of walls in a specific direction becomes possible at arbitrarily small d.c. current density and in materials with arbitrarily small Hall angle and arbitrarily large coercive field. At external fields large enough to force successive walls to move in opposite directions, the ’’excess’’ resistivity δρ associated with walls decreases. Inversely, the presence of a d.c. current and associated dragging forces changes the macroscopic magnetic properties: for example, the coercive field decreases or even vanishes. We also treat the case of dragging of walls by an a.c. transport current of angular frequency ω. Reversible bowing of pinned walls is induced at arbitrarily small current magnitude. At small current, δρ decreases with increasing frequency according to δρ (ω) =δρ (0) ωo/(iω+ωo), where ωo is a characteristic frequency of order 104 rad./s. in the case of pure metals at low temperature.