Topological skyrmions and the manipulation behavior studied by Lorentz TEM
| Date/Time: | Thursday, 05 Oct 2017 from 4:10 pm to 5:00 pm |
|---|---|
| Location: | Physics 003 |
| Phone: | 515-294-7377 |
| Channel: | College of Liberal Arts and Sciences |
| Actions: | Download iCal/vCal | Email Reminder |
Magnetic skyrmions have drawn particular attention due to the topologically stable
nanometric spin textures together with a variety of manipulation options, thereby
prompting the production of next-generation spintronic devices. The experimental
study of the magnetic skyrmions was pioneered in B20 chiral magnets, where the
Dzyaloshinshy-Moriya interaction (DMI) plays an important role due to the broken
inversion symmetry of noncentrosymmetric structure, but mostly in a limited
temperature-magnetic field region below room termperature. The topological
nanometer domains were further explored in several classes of materials including
ferromagnetic multilayers, artificially-patterned films, and uniaxial dipolar bulk
magnets to get better skyrmion stability.
In this talk, the biskyrmion evolution in a hexagonal MnNiGa magnet is
demonstrated over an extremely wide temperature range of 16K-338K by direct real-
space Lorentz TEM. After an optimized thermal manipulation, robust high-density
biskyrmions can be obtained at zero magnetic field due to the topological protection
and the increased energy barrier. The skyrmion multilayers easily-grown by sputtering
show potentials because the magnetic parameters, spin-orbit coupling (SOC), and
other magnetic interactions can be easily engineered by the layer material, layer
thickness, and trilayer repetition numbers. Here, the robust high-density skyrmions
are electromagnetically generated from the Pt/Co/Ta multilayers using Lorentz
transmission electron microscopy (TEM). The skyrmion density is tunable and can be
significantly enhanced. Remarkably, these generated skyrmions after the optimized
manipulation sustain at zero field with both the in-plane current and perpendicular
magnetic field switched off.