October 8, 2015

Computer memory concepts in low-dissipation magnetic information storage or skyrmionics

 (a) The hybrid structure consists of Co dots (red) on top of Co/Pd PMA underlayer (grey) where the
in-plane spin texture of the Co dots (purple arrows) is imprinted into an irradiated Co/Pd region
(light blue) underneath the dots (tilted blue arrows). Green and yellow arrows indicate the moments in
the Co/Pd underlayer and the core region of the (imprinted) vortex, respectively. Major in-plane
(open symbols) and perpendicular (solid symbols) hysteresis loops are shown for (b) the Co/Pd
underlayer as grown, (c) the irradiated Co/Pd witness sample and (d) the hybrid Co+Co/Pd sample.

(October 8, 2015)

The topological nature of magnetic skyrmions leads to extraordinary properties that provide new insights into fundamental problems of magnetism and exciting potentials for novel magnetic technologies. Prerequisite are systems exhibiting skyrmion lattices at ambient conditions, which have been elusive so far. Here, we demonstrate the realization of artificial Bloch skyrmion lattices over extended areas in their ground state at room temperature by patterning asymmetric magnetic nanodots with controlled circularity on an underlayer with perpendicular magnetic anisotropy (PMA). Polarity is controlled by a tailored magnetic field sequence and demonstrated in magnetometry measurements. The vortex structure is imprinted from the dots into the interfacial region of the underlayer via suppression of the PMA by a critical ion-irradiation step. The imprinted skyrmion lattices are identified directly with polarized neutron reflectometry and confirmed by magnetoresistance measurements. Our results demonstrate an exciting platform to explore room-temperature ground-state skyrmion lattices.

The unique spin texture in magnetic skyrmions leads to a host of fascinating phenomena due to the topologically protected quantum state and emergent electromagnetic field, offering great potential for novel concepts in low-dissipation magnetic information storage or skyrmionics. For example, the recent experimental observation that current-driven skyrmion crystal motion only requires current densities that are several orders of magnitude smaller than that necessary for typical current-driven domain wall motion, has sparked intense interest in the field.

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