June’07 issue of Physics today features an illuminating review by Chien, Zhu & Zhu of topic of Nanopatterned magnets.
Much of it relates to the work done by nanomagnetism group at Argonne. Basic idea is that in >100nm pancake-flat (thickness ~10 nm) ferromagnetic disks often minimize magnetostatic energy by forming the whirl-like close-loop magnetization patterns known as “vortices” (not to be confused with all kinds of other vortices, such as type-II superconductors). Nanosized or more symmetric ferromagnetic particles typically form single-domain magnetization state, which is less interesting. But vortices can have some interesting dynamic properties. In elliptical magnetic pancakes equilibrium states call for two or more vortices – and even in the case of just two vortices their interactions can get quite complicated.
The same June issue of Physics Today features a review of zeptoliter pipette article mentioned on this site previously (here and here), which also mentions yours truly by name. Friso sounds skeptical, and his criticism may very well be valid – however the role of surface segregation is not easy to address in these type of nanoscopic systems.