Vortex is ubiquitous in nature including spiral arms of galaxy, planet rotation, hurricane (tornado). A vortex is a typical and well-known magnetic domain structure in dimensionally confined nanostructures with a symmetry determined by its polarity and circulation.
Reversible control of low-dimensional spin structures at nanoscale with low energy consumption is highly desirable for future applications of spintronic devices. Especially, magnetic vortex at nanoscale has been explored for the next-generation data-storage devices.
For the past decades, magnetic field and spin-polarized current have been employed to flip the core and/or reverse circulation of vortex. However, the electric-field deterministic control of a magnetic vortex, which offers much higher storage density and much lower power consumption, is challenging due to the absence of planar magnetic anisotropy of the spin structure.
Chinese researchers discover a deterministic reversal of magnetic vortex circulation in a Ni79Fe21 (NiFe) island on top of a layered-perovskite Bi2WO6 (BWO) thin film using an electric field. The space-varying strain from BWO film under a bi-axial planar electric field drives the magnetic vortex circulation reversal in this magnetoelectric device.
Phase-field simulation directly reveals the mesoscale dynamic reversal mechanism: the traveling strain drags the vortex core from its center to the edge of the NiFe island, then a new core emerges with opposing vortex circulation, leading to the vortex circulation reversal.
This study provides a new framework to deterministically manipulate nanoscale chiral spin texture (vortex, skyrmions etc.) with ultralow-energy consumption. Especially in physical mechanism research, it revealed new magnetoelectric coupling mechanism for more efforts to realize the electric-field control of order parameters (charge, spin and orbital) in functional thin film devices in future.
The work in Beijing Normal University is supported by the National Key Research and Development Program of China (2016YFA0302300), the National Natural Science Foundation of China (11974052, 51972028) and the support from CAS Interdisciplinary Innovation Team.
R.R. is funded by the Director, Office of Science, Office of Basic Energy Sciences, Materials Science and Engineering Department of the US Department of Energy (DOE) in the Quantum Materials Program (KC2202) (DE-AC02-05CH11231).
J.L. acknowledges the support by the Science Alliance Joint Directed Research & Development Program and the Transdisciplinary Academy Program at the University of Tennessee. Use of the Advanced Light Source is supported by the Director, Office of Science, Office of Basic Energy Sciences, of the US DOE (DE-AC02-05CH11231).