The peak velocity of a domain wall in a magnetic bubble film under a large in-plane field

Abstract

When a magnetic field is applied to a domain wall in a bubble domain film, so that it is parallel to the plane of the film and perpendicular to the plane of the wall, very high peak velocities may be observed. It is shown that this behaviour follows from a very simple solution to the Landau‐Lifshitz equation and that this solution is in better agreement with the experimental data than earlier models.

Domain Wall Mass in Magnetic Bubble Films under Large In-Plane Fields

“…while the 2 component of ( 2 ) establishes bhe same relat'ionship, which applies when vY is a constant [29]. We must now restrict our argument to the special case of low drive so that yi may be assumed small and (12) and (13) linearised by setting sin ( V J ) =: y and cos ( y ) = 1.…”

“…The transition from an infinite niediuiii to a thin layer would nornially have a considerable effect upon the wall dynamics [12, 14, 33 to 351 because the wall structure can no longer be assumed one-dimensional, as described by (3) and (4). The yrohleni is no easier when a small in-plane field is applied, below p O H s [36], but for large inplane fields, between poM, and polcI,Q, it is possible to assume a one dimensional wall structure [29,301 and proceed with the problem in a fairly simple way. This is fortunate because the experimental data was obtained under large in-plane fields too and these fields were directed either along y [16 to 221 or along z [23 to 281.…”

“…With these assumptions the x and y coniponents of ( 2 ) both yield 5 ) , (B), and ( 7 ) . We now restrict our discussion to motion near the peak velocity, which was the subject of [29], where it was shown that, as B,/poN, tends towards its maximum possible value Q, the domain wall may move a t a peak velocity for which yi tends to be closer and closer to z . We may then write yl = yo + yil in (25) and (26) where yo = z and yil is a small angle for which sin w1 =: y1 and cos yil x 1.…”

“…Equation (28) shows that the way in which the effective wall mass, the coefficient of dv,/dt, depends upon the in-plane field B, is much more complicated than in the previous case involving B,. This is because the angle yo is a function of both B, and B, [29]. For example, at the peak velocity itself, yo has a value Go given by…”

“…This is the case in which a straight domain wall is stabilised in a magnetic bubble domain film, either by means of an externally applied field gradient El6 to 221 or by making bhe wall one of a set of parallel domain walls 123 to 281. The interesting feature of these two particular experimental configurations is that a large in-plane field may be applied, either perpendicular or parallel to the wall plane, and this greatly extends the range of applied drive fields and wall velocities which may be investigated [29].…”