Editor's Summary
19 January 2006
Artificial spin ice
When a number of interactions compete within a system they can't all prevail, so the resolution of 'frustrated' forces is an important determinant of the overall behaviour of a system. In particular, geometrical frustration among spins in magnetic systems can lead to exotic effects such as 'spin ice', a state where atomic magnetic moments mimic the frustration of hydrogen ion positions in water ice. Wang et al. have created artificial spin ice using lithographically fabricated arrays of nanoscale magnets. Magnetic moments in the lattice follow the two [pointing]-in/ two-out 'ice rule' typical of spin ice. With this model it is possible to study frustration in great detail; this is relevant to magnetic recording, where ferromagnetic elements are being pushed to ever higher densities. On the cover, a magnetic force microscopy representation of the magnetization pattern of artificial spin ice: plateaus and valleys show regions of opposite magnetization.
News and Views: Condensed-matter physics: Great moments in disorder
An array of nanomagnets has been designed to resemble the disordered magnetic state known as 'spin ice'. This could transform our understanding of disordered matter and, potentially, lead to new technologies.
Steven T. Bramwell
doi:10.1038/439273a
Letter: Artificial 'spin ice' in a geometrically frustrated lattice of nanoscale ferromagnetic islands
R. F. Wang, C. Nisoli, R. S. Freitas, J. Li, W. McConville, B. J. Cooley, M. S. Lund, N. Samarth, C. Leighton, V. H. Crespi & P. Schiffer
doi:10.1038/nature04447
