Room-temperature stabilization of antiferromagnetic skyrmions in synthetic antiferromagnets

Abstract

Room-temperature skyrmions in ferromagnetic films and multilayers show promise for encoding information bits in new computing technologies. Despite recent progress, ferromagnetic order generates dipolar fields that prevent ultrasmall skyrmion sizes, and allows a transverse deflection of moving skyrmions that hinders their efficient manipulation. Antiferromagnetic skyrmions shall lift these limitations. Here we demonstrate that room-temperature antiferromagnetic skyrmions can be stabilized in synthetic antiferromagnets (SAFs), in which perpendicular magnetic anisotropy (PMA), antiferromagnetic coupling and chiral order can be adjusted concurrently. Utilizing interlayer electronic coupling to an adjacent bias layer (BL), we demonstrate that spin-spiral states obtained in a SAF with vanishing PMA can be turned into isolated antiferromagnetic skyrmions. We also provide model-based estimates of skyrmion size and stability, showing that room-temperature antiferromagnetic skyrmions below 10 nm in radius can be anticipated in further optimized SAFs. Antiferromagnetic skyrmions in SAFs may thus solve major issues associated with ferromagnetic skyrmions for low-power spintronic devices.

Chiral edge currents for ac-driven skyrmions in confined pinning geometries

“…Other methods of introducing confining boundaries in the sample include using inhomogeneous pinning strength so that skyrmions in one region of the sample are more strongly (or less strongly) pinned than skyrmions in adjacent regions. It would be interesting to examine the effects of confinement on different types of skyrmions, such as antiferromagnetic skyrmions [75][76][77]. If the Magnus force is absent, the skyrmion dynamics would be con- sistent with what is found in an overdamped system and the edge transport would be absent.…”

Magnetic Skyrmions in a Hall Balance with Interfacial Canted Magnetizations

“…[ 31,32 ] Unfortunately, completely compensated magnetizations in ideal antiferromagnets result in challenges related to the detection and manipulation of antiferromagnetic skyrmions. [ 33–35 ] Fortunately, chiral behavior including interlayer Dzyaloshinskii–Moriya interactions (DMI) and stabilized skyrmions has been demonstrated in synthetic antiferromagnets (SAFs), [ 36–39 ] where the alignment of the magnetic moments can be tuned by manipulating two ferromagnetic layers coupled antiferromagnetically. [ 40,41 ] However, the microscopic origin of skyrmion generation is complicated, where opposite skyrmions in SAFs with two ferromagnetic layers have been theoretically proposed.…”

Noncollinear spintronics and electric-field control: a review

“…Thus, how to attain a stable nanoscale skyrmion under room temperature and a small applied field is a crucial task for device applications. Recently, Legrand et al [31] utilized magnetic force microscopy to image the skyrmions in the synthetic antiferromagnets at room temperature ( Fig. 3).…”

“…MFM observations of the BL-SAF system under external applied perpendicular field for μ0Hext = g 20 mT, h 60 mT and i 100 mT. [31] Unusual bulge and dent in the Hall resistance curves as a function of magnetic field are considered to be the features of the topological Hall effect, which stems from the scalar spin chirality in real space and is extensively utilized to detect the presence of chiral spin structure such as skyrmions. In 2009, Neubauer et al [21] reported that the topological Hall effect in the A phase of the transition metal compound MnSi, which testified the skyrmions structure with topological properties ( Fig.…”