Real-Space Observation of Skyrmion Lattice in Helimagnet MnSi Thin Samples

TLDR

Observing and characterizing spin distributions on the nanometer scale is crucial for understanding nanomagnetism and its spintronic applications. The authors used in situ Lorentz microscopy to study the helix‑to‑skyrmion transition in MnSi thin samples derived from bulk material. At zero field below 22.5 K stripe domains appear, while a 6‑fold symmetric skyrmion lattice with an 18‑nm lattice constant emerges at 0.18 T and remains stable over a broad temperature and field range compared to bulk MnSi.

Abstract

Observing and characterizing the spin distributions on a nanometer scale are of vital importance for understanding nanomagnetism and its application to spintronics. The magnetic structure in MnSi thin samples prepared from a bulk, which undergoes a transition from a helix to a skyrmion lattice, was investigated by in situ observation using Lorentz microscopy. Stripe domains were observed at zero applied field below 22.5 K. A skyrmion lattice with 6-fold symmetry in real space appeared when a field of 0.18 T was applied normal to the film plane. The lattice constant was estimated to be 18 nm, almost identical to the helical period. In comparison with the marginally stable skyrmion phase in a bulk sample, the skyrmion phase was stable over a wide range of temperatures and magnetic fields in the thin samples.