Magnetic skyrmions are proposed as binary information carriers in racetrack-type memory device schemes. Therefore, the manipulation of skyrmion arrays in a shift-register-like fashion is one of the key technical requirements for practical device applications. Though moving skyrmions by spin transfer torque has been proven to be effective, the electrical current will eventually dissipate in the form of Joule heat. Here, we demonstrate local Joule heating-free method of manipulation that can translate skyrmions via a magnetic field gradient. A circular field gradient alone is sufficient to drive collective and continuous rotation of the skyrmion lattice. We were able to unambiguously confirm the motion in an in-situ resonant magnetic scattering experiment, as shown in Fig.1. The skyrmion lattice diffraction peaks hereby undergo a continuous rotational motion, generated purely by a set of permanent magnets. We further experimentally rule out other possible driving forces, such as thermal gradients, as well as x-ray-induced effects. We present a theoretical analysis of the skyrmion motion in support of our observations. The rotational motion is accompanied by a skyrmion lattice domain dynamics, which will be discussed in the context of complementary Lorentz transmission electron microscopy experiments.

FIG 1: Real-time evolution of the skyrmion lattice peaks rotating in a circular field gradient.