Successful PhD defence of Dr. Zihan Yin
Tuning magnetic skyrmions in low-dimensional materials
Congratulations to Zihan Yin, who defended her doctoral thesis, "Investigations of Néel-type Skyrmions in Low-dimensional Systems," at the Max Planck Institute of Microstructure Physics on 19 June 2026.
Skyrmions are nanoscale magnetic whirls. Small, stable, and movable by low currents. That mix makes them candidates for a range of future low-power spintronic devices, among them the racetrack memory proposed by NISE director Stuart Parkin.
Yin's work creates and controls Néel-type skyrmions using a single lever: a strain gradient. Strain that varies through a material breaks the inversion symmetry, generating the Dzyaloshinskii–Moriya interaction (DMI) that twists neighbouring spins, and so stabilises the skyrmions.
She showed this in two systems, both built on the same freestanding Co-Al / Ir-Al membrane (the metallic alloys cobalt-aluminium and iridium-aluminium): one uses its flat areas, the other its wrinkled, three-dimensional areas. In the flat system, varying the thickness of the buffer layer tunes the epitaxy-induced strain gradient, and with it the skyrmions. In the wrinkled system, the three-dimensional curvature makes a mechanically-induced strain gradient vary across each wrinkle, extending strain-gradient control of skyrmions into three-dimensional geometries, a step toward potential 3D spintronic applications.
She imaged the magnetism directly with Lorentz transmission electron microscopy, chosen for its direct imaging and its nanoscale resolution; tilting the sample also lets it distinguish Néel-type skyrmions from Bloch-type ones.
"I really enjoy using the transmission electron microscopy to analyse the material and understand the physics principles behind it," Yin says.
She has extended her time at the institute as a postdoc.
The thesis was supervised by Prof. Stuart Parkin and reviewed by Prof. Mathias Kläui (Johannes Gutenberg University Mainz) and Prof. Ingrid Mertig (Martin Luther University Halle-Wittenberg).
