Stripe-domain dynamics in bubble-domain circuits

It is widely known that bubble domains can exist when the bias field is between the elliptic instability (runout) field H
e
and the bubble collapse field H
bc
. Values for H
e
and H
bc
were calculated by Thiele. It is not widely recognized that long stripe domains can also exist in the bottom 20% of this range. Stripes are stable up to the "stripe contraction" field, H
sc
, which is about 0.02 M/μ
0
above H
e
for thickness over intrinsic length,
h/l
, values from 4 to 10. (H
bc
is about 0.10 M/μ
0
above H
e
.) Values for H
sc
were calculated by Kooy and Enz of Philips Research Labs. in 1960, although the importance of their result to bubble-domain devices was not apparent at the time. The velocity of the domain tip during stripout and contraction such as occurs during domain detection or transfer is important for calculating maximum circuit speeds. This is given by
V = cG (H-H_{sc})
, where
H
is the field (bias field plus local field from currents or Permalloy elements),
G
is the wall mobility, and
c
is a constant approximately equal to 0.5.