Fig. 1.

The work by Yu et al. (2) in PNAS reveals that changes of the helicity (i.e., the direction of rotation) are common in magnetic films. The small arrows in A show a magnetic helix with reversal of its helicity (i.e., of the direction of rotation). The helix winds first by 180° in the clockwise direction and then, by 180° in the counterclockwise direction. In small magnetic fields, magnetic bubbles form with a characteristic winding of the magnetic structure. B–D show such configurations (so-called skyrmions) schematically, where the magnetization in the center is opposite to the magnetization in the edge. B and C differ only by their helicity. In B and C, there is only one sense of rotation (i.e., one fixed helicity), whereas in D, an extra twist of the magnetization gives rise to a reversal of the helicity inside the skyrmion.