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Supplementary information

Supplementary figure 1: Domain wall cascade switching. Majority of bars switch from black to white in

cascades at 43.5Oe and 46.0Oe. The bars remain black mid array at 46 Oe must switch by intraarray

local domain wall nucleation. White indicates a magnetisation component in the negative x-direction,

black indicates a magnetisation component in the positive x-direction.

45 Oe 45.5 Oe

46 Oe 46.5 Oe

47 Oe 47.5 Oe

40.5 Oe 41.5 Oe

43.5 Oe42.5 Oe

44 Oe 44.5 Oe

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Supplementary Figure 2: OOMMF Simulations of a Monopole defect under magnetic pressure.

Micromagnetic simulations of a -3q monopole defect in the application of an applied magnetic field

close to Hd. Note that the zero temperature nature of the OOMMF code means that to make meaningful

comparison to the experimental data, the field scale shown here has been normalised to the monopole

depinning field in the text.

10mT

50mT 52mT

0mT

(a) (b)

(c) (d)