Geometrically Tailored Skyrmions at Zero Magnetic Field in Multilayered Nanostructures

Abstract

Magnetic skyrmions are chiral spin structures recently observed at room temperature in multilayer films. Their topological stability will enable high scalability in confined geometries-a sought-after attribute for device applications. Despite numerous theoretical studies examining sub-100-nm Néel skyrmions in nanostructures, in practice their ambient stability and evolution with confinement and their magnetic parameters remain to be established. Here we present the zero-field stabilization of sub-100-nm room-temperature Néel-textured skyrmions confined in Ir/Fe(x)/Co(y)/Pt nanodots over a wide range of magnetic and geometric parameters. The zero-field skyrmion size, here as small as approximately 50 nm, can be tailored by a factor of 4 with variation of dot size and magnetic interactions. Crucially, skyrmions with differing thermodynamic stability exhibit an unexpected dichotomy in confinement phenomenologies. These results establish skyrmion phenomenology in multilayer nanostructures, and prompt the synergistic use of magnetic and geometric parameters to achieve desired properties in devices.

Electric-field-driven non-volatile multi-state switching of individual skyrmions in a multiferroic heterostructure

“…However, few skyrmions are retained at zero magnetic field. This feature further suggests that the magnetic hysteretic effect in our experiments mainly originates from the geometrical pinning effect of the nano-dots, as reported in the previous literatures 9 , 39 , 40 . For the non-volatility of vortex, the case is different.…”

Visualizing the strongly reshaped skyrmion Hall effect in multilayer wire devices

“…The sharp tip profile (diameter ~30 nm), ultra-low moment (~80 emu/cm 3 ), and lift heights of 20–30 nm used during scanning provided high-resolution MFM images while introducing minimal stray field perturbations. Our earlier works have established MFM as a reliable tool for imaging sub-100 nm skyrmions in multilayer films 6 , 45 . In situ electrical pulsing and imaging were carried out in our custom-designed platform consisting of a Tektronix TM AFG3252 pulse generator, SRS TM SIM954 inverting amplifier, Tektronix TM TDS 7404 oscilloscope and the microscope.…”

Isolated zero field sub-10 nm skyrmions in ultrathin Co films

“…Experimental evidence of isolated zero-field skyrmions has been obtained recently in remanence: whereas in a ferrimagnetic material the skyrmion diameter was reported to go down to 16 nm 27 , in FM multilayers the observed skyrmions had a diameter on the order of 100 nm 21 . Isolated zero-field skyrmions were also stabilized in ferromagnets by confinement 19 with diameters down to 50 nm 28 , or in an effective magnetic field due to interlayer exchange coupling 29 where skyrmions with diameters of about 200 nm have been reported 30 . However, there are no reports on isolated zero-magnetic field skyrmions in the virgin state of a FM material, corresponding to the predicted metastable skyrmions.…”