Relativistic kinematics of a magnetic soliton

Abstract

Magnetic special relativity Magnetic materials have domains, patches of ordered spins that are separated from one another by boundaries called domain walls. These boundaries can be driven by electrical currents, a phenomenon forming the basis of the so-called racetrack memories. The speed of the domain walls has steadily increased as experimenters have perfected these devices. Caretta et al. now show experimentally that this speed is fundamentally limited (see the Perspective by Daniels and Stiles). Just as no object can travel faster than the speed of light, the speed of the domain walls saturates to a constant determined only by the properties of the magnetic host material. Science , this issue p. 1438 ; see also p. 1413