Realization of isolated and high-density skyrmions at room temperature in uncompensated synthetic antiferromagnets.

Magnetic skyrmions are swirling spin textures with nontrivial spin topology and novel physical properties that show promise as an essential building block for novel spintronic applications. Skyrmions in synthetic antiferromagnets (SAF) have long-term been proposed to have many advantages than those in ferromagnetic materials, which suffer from fundamental limits for size and efficient manipulation. Thus experimental realization of skyrmions in SAF is intensely pursued. Here we report the observation of zero-field stable magnetic skyrmions at room temperature in SAF [Co/Pd]/Ru/[Co/Pd] multilayers with Lorentz transmission electron microscope (L-TEM), where uncompensated moments of the SAF provide a medium for the skyrmion characterization. Isolated skyrmions and high-density skyrmions via magnetic field and electromagnetic coordinated methods have been observed, respectively. These created high-density skyrmions sustain at zero-field even both the in-plane current and perpendicular magnetic field are removed. The use of skyrmions in SAF would advance the process towards practical non-volatile memories based on spin topology.