Figure 1.
(a) Schematic of a rectangular zigzag wire with a head-to-head (HH) domain wall (DW) at the vertex, associated field HDW, and a trapped magnetic particle (gray circle). (b) Array of zigzag wires patterned on platform with perpendicular (Hz) and in-plane (H//) magnetic fields. Sketch in (a) is an enlarged view of the dotted circle around a vertex. (c) Schematic of electromagnets and coil to create H// and Hz. Cell movement observed by optical microscope (Reichert) with 20× objective lens and high speed camera. (d) Image of superparamagnetic spheres (2.8 μm diameter, dark circles) selectively attracted from solution and trapped only at HH and TT (tail-to-tail) domain walls under no external fields. The FeCo wires patterned on Si are 2 μm wide, 40 nm thick with 16 μm between adjacent vertices.