Observation of Robust Néel Skyrmions in Metallic PtMnGa

Over the past decade the family of chiral noncollinear spin textures has continued to expand with the observation in metallic compounds of Bloch-like skyrmions in several B20 compounds, and antiskyrmions in a tetragonal inverse Heusler. Neel like skyrmions in bulk crystals with broken inversion symmetry have recently been seen in two distinct nonmetallic compounds, GaV4 S8 and VOSe2 O5 at low temperatures (below approximately 13 K) only. Here, the first observation of bulk Neel skyrmions in a metallic compound PtMnGa and, moreover, at high temperatures up to approximately 220 K is reported. Lorentz transmission electron microscopy reveals the chiral Neel character of the skyrmions. A strong variation is reported of the size of the skyrmions on the thickness of the lamella in which they are confined, varying by a factor of 7 as the thickness is varied from approximately 90 nm to approximately 4 microm. Moreover, the skyrmions are highly robust to in-plane magnetic fields and can be stabilized in a zero magnetic field using suitable field-cooling protocols over a very broad temperature range to as low as 5 K. These properties, together with the possibility of manipulating skyrmions in metallic PtMnGa via current induced spin-orbit torques, make them extremely exciting for future spintronic applications.