Vortex dynamics in arrays of nanomagnets

Observation of vortex dynamics in arrays of nanomagnets.
W. Yu, P. S. Keatley, P. Gangmei, M. K. Marcham, T. H. J. Loughran, R. J. Hicken, S. A. Cavill, G. van der Laan, J. R. Childress, and J. A. Katine
Phys. Rev. B 91, 174425 (2015)

TRSKM images, XPEEM images, and SEM images of arrays of 250-nm squares with separation of 500 nm in (a) and (b), and 50 nm in (c). After acquisition of the TRSKM images in (a), the equilibrium state was reinitialized before acquiring the TRSKM images in (b). In all TRSKM images the horizontal white bar has length of 1 μm. In (c) the white arrows in the TRSKM images denote regions of contrast with size comparable to, or larger than, that of a single element, while the dashed white rectangle in the XPEEM image highlights a cluster of elements with vortex equilibrium states. (d) Enlarged view of (c), in which the black grid position is a guide to the eye to show where the individual elements lie, and the white boxes highlight regions of contrast